PAPERmaking! Vol.8 No.1 2022 by pita.co.uk

PAPERmaking! The e-magazine for the Fibrous Forest Products Sector

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Paper Technology International®

Volume 8 / Number 1 / 2022

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

CONTENTS: FEATURE ARTICLES: 1. Tissue: Energy saving by efficiency scheduling under Time-of-Use tariffs. 2. Pulping: Using Green Chemistry for a Circular Economy. 3. Nanocellulose: Application of NCC suspensions to papermaking. 4. Fillers: Nano-silica papermaking fillers prepared from rice straw ash. 5. Corrugated: Modelling warp in corrugated cardboard. 6. Pulp: Coffee silverskin as a pulp substitute in the context of Circular Economy. 7. Wood Panel: Flexural rigidity and modelling of moduli of elasticity of OSB. 8. Water Treatment: A new strategy for handling papermaking waste water. 9. Biopolymers: Sustainable additives in pulp and paper – a comprehensive review. 10. Leadership: The 8 most common leadership styles. 11. Management: How to develop a project plan – 12 steps to success. 12. Meeting Etiquette: 8 rules to improve professional meetings. SUPPLIERS NEWS SECTION: News / Products / Services: Section 1 – PITA Corporate Members: ABB / ARCHROMA / BUCKMAN / VALMET Section 2 – PITA Non-Corporate Members VOITH DATA COMPILATION: Events: PITA Courses & International Conferences / Exhibitions Installations: Overview of equipment orders and installations since November 2021 Research Articles: Recent peer-reviewed articles from the technical paper press Technical Abstracts: Recent peer-reviewed articles from the general scientific press

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper ® Technology International and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Contents

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Energy Saving for Tissue Paper Mills by Energy-Efficiency Scheduling under Time-of-Use Electricity Tariffs 1

ZHIQIANG ZENG , XIAOBIN CHEN AND KAIYAO WANG . Environmental concerns and soaring energy prices have brought huge pressure of energy saving and emission reduction to tissue paper mills. Electricity is one of the main energy sources of tissue paper mills. The production characteristics of tissue paper mills make it easy to decrease energy cost by using time-ofuse (TOU) electricity tariffs. This study investigates the bi-objective energy-efficiency scheduling of tissue paper mills under time-of-use electricity tariffs, the objectives of which are makespan and energy cost. First, considering the processing energy cost, setup energy cost, and transportation energy cost, an energy cost model of a tissue paper mill under TOU electricity tariffs is established. Second, the energy-efficiency scheduling model under TOU electricity tariffs is built based on the energy cost model. Finally, on the basis of decomposition and teaching–learning optimization, this study proposes a novel multi-objective evolutionary algorithm and further combined with the variable neighborhood search to solve the problem. The case study results demonstrate that our study of tissue paper mill energy saving is feasible, and the proposed method has better performance than the existing methods. Contact information: 1 Faculty of Intelligent Manufacturing, Wuyi University, Jiangmen 529020, China. 2 College of Chemical and Material Engineering, Quzhou University, Quzhou 324000, China. Processes 2021, 9, 274. https://doi.org/10.3390/pr9020274 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Article 1 – Tissue & Energy

processes Article

Energy Saving for Tissue Paper Mills by Energy-Efﬁciency Scheduling under Time-of-Use Electricity Tariffs Zhiqiang Zeng 1, * , Xiaobin Chen 2 and Kaiyao Wang 1 1 2

Faculty of Intelligent Manufacturing, Wuyi University, Jiangmen 529020, China; wang.kaiyao@outlook.com College of Chemical and Material Engineering, Quzhou University, Quzhou 324000, China; xbchen24264@163.com Correspondence: zhiqiang.zeng@outlook.com

Abstract: Environmental concerns and soaring energy prices have brought huge pressure of energy saving and emission reduction to tissue paper mills. Electricity is one of the main energy sources of tissue paper mills. The production characteristics of tissue paper mills make it easy to decrease energy cost by using time-of-use (TOU) electricity tariffs. This study investigates the bi-objective energy-efﬁciency scheduling of tissue paper mills under time-of-use electricity tariffs, the objectives of which are makespan and energy cost. First, considering the processing energy cost, setup energy cost, and transportation energy cost, an energy cost model of a tissue paper mill under TOU electricity tariffs is established. Second, the energy-efﬁciency scheduling model under TOU electricity tariffs is built based on the energy cost model. Finally, on the basis of decomposition and teaching– learning optimization, this study proposes a novel multi-objective evolutionary algorithm and further combined with the variable neighborhood search to solve the problem. The case study results demonstrate that our study of tissue paper mill energy saving is feasible, and the proposed method has better performance than the existing methods. Citation: Zeng, Z.; Chen, X.;

Keywords: tissue paper mill; energy saving; time-of-use electricity tariffs; multi-objective optimization

Wang, K. Energy Saving for Tissue Paper Mills by Energy-Efﬁciency Scheduling under Time-of-Use Electricity Tariffs. Processes 2021, 9, 274. https://doi.org/10.3390/ pr9020274 Received: 8 December 2020 Accepted: 27 January 2021 Published: 31 January 2021

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁliations.

Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/

1. Introduction The paper industry is an energy-intensive industry. In 2019, its energy consumption reached 1483.2 trillion British thermal units (Btu), of which electricity consumption was 205.3 trillion Btu. [1]. At the same time, the carbon dioxide emissions of the paper industry reached 48 million tons in 2019, accounting for 4.45% of the total carbon dioxide emissions of the manufacturing industry [2]. Under the pressure from environmental degradation and rising energy costs, the papermaking industry is faced with huge energy-saving and emission reducing pressure. Studying the energy-efficiency scheduling under the time-ofuse (TOU) electricity tariffs is of great significance for papermaking enterprises to improve energy efficiency. In general, one day can be divided into three periods based on the electricity demand, namely, the on-peak period, the mid-peak period, and the non-peak period. Due to the imbalance in the demand for electricity, waste will be generated in the off-peak or mid-peak periods, while the demand will exceed the supply during the on-peak period. To deal with this issue, the TOU pricing scheme is used to encourage users to use electricity in the mid-peak period and off-peak period, thus balancing the demand of electricity. In the production process, the electricity consumption of each job is different, indicating that the operation with high electricity consumption is arranged in off-peak or mid-peak periods and the operation with low electricity consumption is arranged in an on-peak period, so that the electricity cost can be decreased. The energy-efficiency scheduling under TOU electricity tariffs is based on above idea, which has attracted more attention in recent years.

4.0/).

Processes 2021, 9, 274. https://doi.org/10.3390/pr9020274

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Mouzon and Yildirim are the pioneers that regard energy consumption as the objective of production scheduling [3]. Energy-efficiency scheduling mainly improves energy efficiency in two ways: reducing energy consumption and reducing energy cost by scheduling. The existing research on energy-efficiency scheduling focuses on how to decrease energy consumption in different stages, such as decreasing the energy consumption in the processing stage, the setup stage, and the standby stage [4–9]. Recently, energy-efficiency scheduling decreases energy cost considering both energy consumption and energy price. Energy-efficiency scheduling under TOU electricity tariffs is an efficient way to reduce energy cost. Scholars have carried out a lot of research on energy-efficiency scheduling under TOU electricity tariffs in different generic manufacturing systems. Simple manufacturing systems, such as single machine and parallel machine, have been studied by many researchers [10–13]. However, there are few reports on complex manufacturing systems, such as flow shop, flexible flow shop, job shop, flexible job shop, etc. [14–16]. The generic manufacturing systems are different from the real manufacturing systems. In order to study the energy-efficiency scheduling models in line with the actual manufacturing system, some scholars have investigated energy-efficiency scheduling in the actual production and manufacturing system, such as hardware manufacturing and iron and steel industry [17–22]. According to different production stages, the energy cost mainly consists of processing energy cost, setup energy cost, standby energy cost, etc. [23]. Many studies discuss processing energy cost, which accounts for the largest proportion of the total energy cost [24,25]. Setup energy cost cannot be ignored in many industries, especially in the processing industry. In addition, transport energy cost may be negligible in many industries, but it cannot be ignored in heavy industry. Setup time and transportation time may span multiple time periods, leading to different electricity prices in the same setup stage or transportation stage. Consequently, it is difficult to build an efficient energy cost model. Many research studies on energy-efficiency scheduling under TOU electricity tariffs fails to consider the setup energy cost and the transportation energy cost. The feasibility of reducing material wastage and energy consumption in tissue paper mills has been proved through production scheduling [26]. Energy consumption in tissue paper mills can be decreased by combining process optimization and production scheduling [27]. However, the previous research fails to consider TOU electricity tariffs. This study investigates the energy-efficiency scheduling under TOU electricity tariffs for tissue paper mills. There are three main contributions in this paper: First, a new mathematical model of energy-efficiency scheduling under TOU electricity tariffs is established for tissue paper mills. Energy cost includes processing energy cost, setup energy cost and transportation energy cost. Second, a novel Multi-Objective Evolutionary Algorithm based on Decomposition and Teaching–Learning-Based Optimization (MOEA/DTL) is proposed, which further improves the performance of the MOEA/DTL by Variable Neighborhood Search (IMOEA/DTLB). Third, the effectiveness of the proposed IMOEA/DTL is verified by carrying out a case study. Lastly, the energy-saving potential of the IMOEA/DTL is evaluated based on a practical scheduling problem in a tissue paper mill. This paper is structured as follows. In Section 2, the production process and the energy-efficiency scheduling of tissue paper mills under electricity tariffs are described. Moreover, an energy cost model under TOU electricity tariffs is built, and the energyefficiency scheduling model under TOU electricity tariffs is built. Section 3 introduces the proposed IMOEA/DTL method. Section 4 verifies the feasibility of the study and the effectiveness of the proposed algorithm by carrying out a case study. Finally, Section 5 summarizes the study and proposes the future research direction. 2. Problem Description and Modeling As shown in Figure 1, the production of a tissue paper mill mainly includes two stages, namely the pulping and papermaking stage and the conversion stage. In the pulping and papermaking stage, the first production unit is the stock preparation system, which is

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composed of a pulper, a refiner, and a chest. The pulper is the first equipment used in the pulping and papermaking stage. The paperboard is first mixed with water and then disintegrated by the pulper to obtain the pulp with a certain concentration. The obtained pulp is stored in the chest (there are usually multiple chests). However, the quality of the pulp disintegrated by the pulper cannot meet the requirements of papermaking. Therefore, it is necessary to further improve the quality of the pulp using the refiner. The pulp obtained by the refiner will be stored in other chests. The pulper and the refiner operate intermittently, which mainly depends on the liquid level of the chest. Afterwards, the pulp is sent to the forming sector through the approach flow system. The forming sector removes part of the water, and finally, the paper is formed. Next, the paper is further dehydrated by the press section. The dryness of the paper from the press section falls far short of the requirements. Paper is dried in the dryer section to make the dryness of the paper meet the requirements. The last step of the pulping and papermaking stage is the winding section. The paper is reeled by the reel cylinder, thus forming the parent roll. The parent roll will be further processed in the conversion stage.

Figure 1. Production process of tissue paper mills.

In the conversion stage, a certain number of parent rolls are simultaneously rolled into reels using the winder, and the number of the parent rolls depends on the numbers of paper layers in the finished product. The reel paper is cut into small reels with a cutter. Finally, the small reels are packaged into the finished product by the packaging machine. Discrete production mainly occurs in the pulping process and the processing between the pulping and papermaking stage and the conversion stage. The processing is continuous in the papermaking or conversion stage. The interval time between two stages is uncertain. Different from other flow shops, only when enough parent rolls are produced in the papermaking stage can the conversion stage be started, rather than after finishing a roll of parent roll in the papermaking stage. The interval time between two stages is related to the product characteristics and the machine speed. Too long of an interval time

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will increase the pressure on work-in-process inventory. However, a short interval time is likely to cause frequent downtime of the machine in the conversion stage. Therefore, it is important to determine the optimal interval time in the production scheduling. The scheduling of a tissue paper mill, which is two-stage flexible flow shop scheduling, is composed of the pulping and papermaking stage and the conversion stage. Each job is processed by a production line in the pulping and papermaking stage and a production line in the conversion stage. The energy consumption in the processing stage accounts for the vast majority of energy consumption in tissue paper mills. Product characteristics can determine the processing energy consumption. Different product characteristics mean different process parameters, and the energy consumed by machines under different process parameters varies significantly. For example, the products with high grammage will consume more energy in the papermaking stage, and vice versa. Under TOU electricity tariffs, the energy cost can be reduced in two ways: (i) arranging the job to the production line with low processing energy consumption; and (ii) arranging the job with high grammage production in the off-peak or mid-peak period and the job with low grammage production in the on-peak period. When there are two different consecutive jobs, production changeover will occur in tissue paper mills. The parameters of the machine should be adjusted to process the new later job, which will consume a lot of energy in the setup stage. In general, the setup energy cost can be reduced by arranging jobs with lower setup energy consumption processed consecutively. Under TOU electricity tariffs, the setup energy cost can be further reduced by arranging the jobs with higher setup energy consumption processed in the off-peak or mid-peak period and the jobs with lower setup energy consumption processed in the on-peak period. The parent rolls produced in the pulping and papermaking stage should be transported to the conversion stage for further processing. The transport energy consumption is related to the distance between the papermaking line and the conversion line. Similarly, the transportation distance can be shortened to decrease the transport energy cost. Moreover, the transport energy cost can be further reduced by arranging the jobs with high transportation energy consumption in the off-peak or mid-peak period and the jobs with low transportation energy consumption in the on-peak period. Tissue paper mills can decrease the energy cost by utilizing the TOU electricity pricing scheme in job scheduling. Table 1 shows the TOU electricity tariffs in Guangdong, China. Table 1. Time-of-use (TOU) electricity tariffs implemented in Guangdong. Period Type

Time Periods

Electricity Price (CNY/kWh)

Off-peak Mid-peak On-peak

00:00–08:00 08:00–09:00; 12:00–19:00; 22:00–24:00 09:00–12:00; 19:00–22:00

0.3351 0.6393 1.0348

2.1. Energy Cost Modeling According to the characteristics of energy consumption in tissue paper mills, this study mainly considers energy cost from three aspects: processing energy cost, setup energy cost, and transportation energy cost. Processing energy cost is related to processing energy consumption and electricity price. Under the TOU electricity pricing scheme, different electricity prices are set for different periods in a day. This study establishes a processing energy cost model combined with the TOU electricity pricing scheme and the processing energy consumption. The processing energy cost model is as below. EP =

∑ ∑ (EP1 + EP2 + EP3 + EP4) ∗ Oi,j

(1)

j =1 i =1

EP1 = MI N CEIL Si,j − Si,j , FG CEIL Si,j + Ti,j , CEIL Si,j × Ui,j × PFLOOR( MOD(Si,j ,K))

(2)

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EP2 =

FLOOR( MOD (Si,j ,K )+( Ti,j − FIX ( Ti,j ,K )∗K ))

∑

k=CEIL( MOD (Si,j ,K ))

Pk × Ui,j

(3)

EP3 = Si,j + Ti,j − FLOOR Si,j + Ti,j × Ui,j × PFLOOR( MOD(Si,j +Ti,j ,K )) EP4 = FIX Ti,j , K ×

∑

k =1

Pk × Ui,j

(4) (5)

where EP is the processing energy cost, and Equation (1) is the calculation formula of the processing energy cost. The processing energy cost is divided into four parts, namely EP1, EP2, EP3, and EP4. Equation (2) represents the processing energy cost from the start of the job to the next period. Equation (3) represents the processing energy cost from the next period of the start of the job to the previous period of the completion of the job. Equation (4) represents the processing energy cost from the previous period of the completion of the job to the completion of the job. If the job spans for several cycles, Equation (5) represents the processing energy cost of the job in several cycles. m and n are the numbers of production lines and jobs, respectively. Oi,j denotes whether production line j processes job i. Oi,j is set to one when production line j processes job i; otherwise, it is set to zero. CEIL is a function that rounds up to an integer. Ti,j is the processing time of job i in production line j. Si,j is the start time of job i processed in production line j. Function FG has two parameters. When the ﬁrst parameter is equal to the second parameter, FG is set to one; otherwise, it is set to zero. Ui,j represents the power of job i in production line j, Pk represents the electricity price in k period. FLOOR is a function that rounds down to an integer, K is the number of periods, MOD represents modulo operation, and FIX is the quotient operation. The setup time is up to several hours, especially in the pulping and papermaking stage, which cannot be ignored in tissue paper mills. Under the TOU electricity pricing scheme, the machine setup energy cost may be different when the setup occurs at different periods due to different energy prices in different periods. The off-peak or mid-peak period has lower setup energy cost compared with the on-peak period. Moreover, the setup may span multiple periods. The setup energy cost model is formulated as follows: ES =

m Nj

∑ ∑ ES1 + ES2 + ES3 + ES4

(6)

j =1 i =1

ES1 = MI N CEIL Fi−1,j − Fi−1,j , FG CEIL Fi−1,j + TSi,i−1,j , CEIL Fi−1,j ×USi,i−1,j × PFLOOR( MOD( Fi−1,j ,K)) ES2 =

FLOOR( MOD ( Fi−1,j ,K )+( TSi,i−1,j − FIX ( TSi,i−1,j ,K )×K ))

∑

k=CEIL( MOD ( Fi−1,j ,K ))

Pk × USi,i−1,j

ES3 = Fi−1,j + TSi,i−1,j − FLOOR Fi−1,j + TSi,i−1,j × USi,i−1,j × PFLOOR( MOD( Fi−1,j +TSi,i−1,j ,K)) ES4 = FIX TSi,i−1,j , K ×

∑

k =1

Pk × USi,i−1,j

(7)

(8)

(9)

(10)

where ES represents the setup energy cost, and Equation (6) is the calculation formula of the setup energy cost. The setup energy cost is divided into four parts, namely ES1, ES2, ES3, and ES4. Equation (7) represents the setup energy cost from the start of the setup to the next period. Equation (8) represents the setup energy cost from the next period of the start of the setup to the previous period of the completion of the setup. Equation (9) represents the setup energy cost from the previous period of the completion of the setup to the completion of the setup. If the setup spans for several cycles, Equation (10) represents the setup energy cost of the job in several cycles. Nj represents the number of

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jobs processed in production line j, Fi−1,j is the completion time of job i − 1 in production line j, TSi,i−1,j is the setup time in the conversion from job i − 1 to job i in production line j. USi,i−1,j is the power when job i − 1 is converted to job i in production line j. In tissue paper mills, the parent roll produced in the papermaking line should be transported to the conversion line for further processing. However, the distance between papermaking lines and conversion lines is different. The longer the distance, the higher the energy cost of transporting the parent roll from the papermaking line to the conversion line. The transportation time in tissue paper mills is up to tens of minutes. In the production scheduling process, it is necessary to consider the processing route with short distance to reduce the transportation energy cost. Under the TOU electricity pricing scheme, the transportation energy cost varies in different time periods. Similarly, the transportation time may span multiple time periods. The transportation energy cost model of tissue paper mills is formulated as below: ET =

n m2

∑∑

i =1 l =1

( TP1 × P1 + TP2 × P2 + TP3 × P3) × Wi × TC TP1 = TP2 = TP3 =

∑ Oi,h , l

ET1(1) + ET2(1) + ET3(1) ET2(s) + ET3(s))

(12)

ET1(2) + ET2(2) + ET3(2) ET2(s) + ET3(s))

(13)

ET1(3) + ET2(3) + ET3(3) ET2(s) + ET3(s))

(14)

∑3s=1 ( ET1(s) + ∑3s=1 ( ET1(s) + ∑3s=1 ( ET1(s) +

ET1(s) = MI N (CEIL (Si,l ) − S i,l , FG ( CEIL(S i,l + Ti,l ), CEIL(Si,l ))) × Q FLOOR MOD Si,j , K , s ET2(s) =

(11)

h =1

FLOOR( MOD (Si,l ,K )+( Ti,l − FIX ( Ti,l ,K )×K ))

∑

Q(k, s)

(15)

(16)

k=CEIL( MOD (Si,j ,K ))

ET3(s) = (Si,l + Ti,l − FLOOR(Si,l + Ti,l )) × Q FLOOR MOD Si,j , K , s ET4(s) = FIX ( Ti,l , K ) ×

(17)

∑ Q(k, s)

(18)

k =1

where ET is the transportation energy cost, Equations (12)–(14) calculate the proportions of the processing time of job i in the off-peak, mid-peak, and on-peak periods to the total processing time, respectively. Equation (15) represents the transportation energy cost from the start of the transportation to the next period. Equation (16) represents the transportation energy cost from the next period of the start of the transportation to the previous period of the complete of the transportation. Equation (17) represents the transportation energy cost from the previous period of the completion of the transportation to the completion of the transportation. If the transportation spans for several cycles, Equation (18) represents the transportation energy cost of the job in several cycles. m1 represents the number of production lines in the pulping and papermaking stage, while m2 is the number of production lines in the conversion stage. TP1, TP2, and TP3 represent the proportions of the processing time of job i in the off-peak, mid-peak, and on-peak periods to the total

processing time, respectively. Wi is the scale of job i. C ∑m1 h=1 Oi,h , l represents energy consumed by transporting job i from papermaking line h to conversion line l. The function Q(k, s) can judge whether the time period k belongs to period type s. The parameter s is the period type, and s values equal to 1, 2, and 3, respectively represent the off-peak, mid-peak, and on-peak period, respectively.

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2.2. Energy-Efficiency Scheduling Modeling In the pulping and papermaking stage or the conversion stage, there are multiple parallel production lines with different speeds. Each job must be first processed in a production line in the first stage and then processed in a production line in the second stage. The pulping and papermaking line or the conversion line only processes one job at a time. In this study, the job cannot be stopped once being processed in the pulping and papermaking line or the conversion line. In addition, the time interval between two stages is uncertain. The scheduling problem is the variant of a two-stage flexible flow shop scheduling problem. According to the production scheduling characteristics of tissue paper mills and the above established energy cost model, the energy-efficiency scheduling model is as below. The model in this study contains two optimization objectives, which are multi-objective optimization problems. Multi-objective optimization problems are different from single-objective optimization problems. The quality of the solution needs to be evaluated through the dominance relationship. When all the objectives of solution S1 are better than all the objectives of solution S2, it can be said that S1 dominates S2. If S1 only has some objectives better than S2, then S1 and S2 are non-dominated. If a solution is not dominated by any other solution, the solution is called a non-dominated solution. The solution to the multi-objective optimization problem is a set of non-dominated solutions.

min( MAX (Ci )) ∀i ∈ {1, 2, . . . , n} min( EP + ES + ET )

(19)

n m1

∑ ∑ Oi,j = 1

(20)

i =1 j =1 n m2

∑ ∑ Oi,j = 1

(21)

i =1 j =1

Ij,l ≥ Fj,l −1 + TSl,l −1,j Bi,2 ≥ Bi,1 + f

∀ j ∈ 1, . . . , m; ∀l ∈ 2, . . . , Nj

l =1

h =1

∑ Vi,l × Oi,l , ∑ Vi,h × Oi,h , Wi

f (v1, v2, w) =

H v1 w v1

−

w v2

H v1

m1 + m2 = m

∀i = 1, . . . , n

v1 ≥ v2 v1 < v2

(22) (23) (24) (25)

∑ Nj = n

(26)

j =1

Formula (19) is the optimization objectives, and there are two optimization objectives, which are makespan and energy cost. Ci is the completing time of the job i in conversion line. Constraint (20) guarantees every job can and must be processed once in the pulping and papermaking line. Constraint (21) guarantees that every job can and must be processed once in the conversion line. Constraint (22) guarantees that every papermaking line or converting line can only process one job at the same time, indicating that only when the previous job and the setup are complete can the next job be started, where Ij,l is the beginning time of the l-th job in production line j. Constraint (23) guarantees there is a time interval between two stages. Bi,1 is the beginning time of job i in the papermaking line, and Bi,2 is the beginning There is a time interval between Bi,1 time of job i in the conversion line. m2 and Bi,2 , where f ∑m1 l =1 Vl × Oi,l , ∑ h=1 Vh × Oi,h , Wi represents the time interval, which is related to the speed of the papermaking line l when processing job i (Vi,l ), the speed of the conversion line h when processing job i (Vi,h ), and the scale of job (Wi ). Formula (24) is the calculation method of the time interval between Bi,1 and Bi,2 , where H represents the value

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of the length of the parent roll multiplying the number of paper layers in ﬁnished products. Formulas (25) and (26) are equality constraints. 3. The Proposed Optimization Algorithm In this section, the MOEA/DTL is proposed based on two outstanding methods, namely teaching-learning-based optimization (TLBO) and MOEA/D. In order to further improve the quality of the solutions, a variable neighborhood search (VNS) algorithm is designed to be combined with the MOEA/DTL to improve the performance of the algorithm (IMOEA/DTL). 3.1. MOEA/DTL MOEA/D uses multiple weight vectors to decompose the multi-objective optimization problem into multiple single-objective sub-optimization problems. When the weight vectors are distributed uniformly, the MOEA/D assumes Pareto optimal solutions with uniform distribution generated by combining the solutions of sub-optimization problems. Every individual is corresponding to a sub-optimization problem in MOEA/D. In each iteration of MOEA/D, each individual exchanges information with neighbors and coevolves [28]. The ﬂow chart of the standard MOEA/D is shown in Figure 2.

Figure 2. The ﬂow chart of Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA/D).

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The input parameters are consistent with the input parameters of the proposed algorithm; refer to the input parameters of the proposed algorithm below. The initialization is the same as the proposed algorithm; refer to the proposed algorithm below. gte xi λi , z is the decomposition approach. There are many decomposition approaches; among them, the boundary intersection approach, Tchebycheff approach, and weighted sum approach are three popular decomposition approaches. The basic idea of TLBO is to simulate the learning process of the class, which is completed in two phases: the teaching phase and the learning phase. Each individual learns from the teacher (the best individual is selected as the teacher) in the teaching phase. Individuals learn from each other (an individual is randomly selected) in the learning phase. The TLBO is originally designed to solve the continuous optimization problem because the formulas used to update individuals in the teaching and learning phase are continuous variable oriented. Some changes should be made when the scheduling problem is solved by the TLBO. This study modiﬁes the TLBO by replacing the update formula by the discrete crossover operation. According to the idea of MOEA/D and TLBO, this study proposes a hybrid method (MOEA/DTL). The Figure 3 shows the ﬂow chart of MOEA/DTL. The details of the proposed MOEA/DTL are shown in Algorithm 1.

Figure 3. The ﬂow chart of Multi-Objective Evolutionary Algorithm based on Decomposition and Teaching–Learning-Based Optimization (MOEA/DTL).

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Algorithm 1 MOEA/DTL 1. Initialize the population scale and the number of subproblems. 2. Initialize the maximum number of iterations (Mt). 3. Initialize a set of N weight vectors with uniform distribution (λ1 , λ2 , . . . , λ N ). 4. Initialize the number of neighbors for every weight vector (T). 5. Set the external population EP = Φ. 6. for each i = 1 to N do 7. The nearest T weight vectors of the i-th weight vector is calculated according to Euclidean distances. 8. Set B(i ) = λ1i , λ2i , . . . , λiT , where B(i ) is the neighbors of λi with T weight vectors. 9. end for , x2 , . . . , x N by a speciﬁc method. 10. Generate x1

11. FV i = F xi is set by the decomposition approach. 12. Set z = (z1 , z2 , . . . , zn ) T , where z j = min1≤i≤ N f j xi , f j xi is the j-th objective of solution

xi . 13. while true do 14. for i = 1 to N do 15. Teaching phase: 16. if xi is not the best individual among its T neighbors 17. An individual from its T neighbors is randomly set as teacher Th with a probability Ps, or an individual is randomly selected from EP as teacher Th with a probability 1-Ps. 18. else 19. An individual is randomly selected from EP as Th. 20. end if 21. A new individual y is generated by a crossover operation from xi and Th. 22. Mutation operation is applied to y with probability Pm to generate a new individual y . 23. for each j ∈ [1, . . . , m] do 24. Set z j = min z j , f j (y ) . If gte y λi , z ≤ gte xi λi , z , set xi = y and FV i = F (y ). 25. end for 26. Learning phase: 27. for each j ∈ B(i ) do 28. if x j is not the best individual in the T neighbors of xi 29. A new individual y is ﬁrst generated by crossover operation from xi and x j . 30. A new individual y is generated by applying the mutation operation to y with probability Pm. 31. else 32. Continue to the next iteration. 33. end if 34. for each j ∈ [1, . . . , m] do 35. 36.

set z j = min z j , f j (y ) . if gte y λi , z ≤ gte xi λi , z

37. Set xi = y and FV i = F (y ). 38. end if 39. end for 40. end for 41. end for 42. Update EP: a new non-dominated set is selected from EP and the new population as the new EP, and get rid of the duplicate solution. If the size of EP is smaller than the setting value, some randomly generated individuals (EP ) are added to EP until the size of EP is equal to the setting value. 43. for each i = 1 to size( EP) do 44. An individual xi is randomly selected from EP − EP , and an individual x j is ranbdomly selected from EP − EP with a probability Pc, or an individual x j is selected from EP with a probability 1 − Pc. 45. A new y is generated by crossover operation from xi and x j .

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Algorithm 1 Cont. 46. Mutation operation is applied to y with probability Pm to generate a new y . 47. end for 48. Update EP: select a new non-dominated set from EP and the new population as the new EP 49. if the stopping criterion is not satisﬁed 50. Continue. 51. else 52. Stop and output EP. 53. end if 54. end while

The weight vectors can determine the quality of solution obtained by MOEA/DTL. With the uniformly distributed weight vectors, the solution obtained by MOEA/DTL is more evenly distributed and closer to the Pareto optimal solution. Thus, the method of generating some weight vectors with even distribution is of great importance to MOEA/DTL. In this study, a number of weight vectors are generated as follows: Step (1) Set γ = γ1 , γ2 , . . . , γ N +1 , where γi = γ1i , γ2i For each i = 0 to N, do: γ1i =

i N,

γ2i = 1 −

i N.

Step (2) Generate weight vectors λ = λ1 , λ2 , . . . , λ N by randomly selecting N vectors from γ. The parameter Ps is one of the important factors affecting the convergence speed of the algorithm. If Ps is too small, it means that most of the teachers are from the global optimal individual, and it is easy to fall into the local optimal value. If Ps is too large, it means that most of the teachers come from the best individuals in the neighborhood, and the convergence speed will be slower. The value of Ps between 0.7 and 0.9 is reasonable. The decomposition approach is also important for MOEA/DTL. The makespan and the energy cost are converted into an objective using the weighted sum approach. The makespan and the energy cost are the two different scalar objectives. Therefore, the decomposition method must have the function of normalization. The decomposition approach is as below: m λi × f j x i − f min j j gi = ∑ (27) max − f min f j =1 j j where gi is the scalar optimization objective of solution xi , f jmax is the maximum of the j-th objective, and f jmin is the minimum of the j-th objective. 3.2. Variable Neighborhood Search With the advantages of high efﬁciency and simple implementation, the Variable Neighborhood Search (VNS) algorithm has been successfully applied in many engineering ﬁelds [29,30]. The VNS algorithm uses the neighborhood structure of different actions to search alternately, thus achieving a good balance between concentration and evacuation. Firstly, the VNS is carried out in a small neighborhood. If the quality of the solution cannot be improved, VNS will be carried out in a larger neighborhood. When a better solution is found, the VNS is conducted in a smaller neighborhood again. The cycle is repeated until the end of the algorithm. The VNS algorithm is simple in principle, easy to implement, and has good optimization performance. The procedure of the VNS algorithm used in this paper is shown in Algorithm 2:

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Algorithm 2 VNS 1. Construct the set of neighborhood structures Si , i = 1, 2, 3. 2. Set the maximum iterations M for searching in the first, second, and third neighborhood structures M1, M2, M3. 3. Set the initial solution. 4. for each i ∈ [1, 2, . . . , M] do 5. for each j ∈ [1, 2, . . . , M1] do 6. Based on the current solution, the first neighborhood structure S1 is used to search for better solutions than the current solution, and it means that the solutions found can dominate the current solution. 7. end for 8. for each j ∈ [1, 2, . . . , M2] do 9. Based on the current solution, the second neighborhood structure S2 is used to search for better solutions than the current solution, and it means that the solutions found can dominate the current solution. 10. end for 11. for each j ∈ [1, 2, . . . , M3] do 12. Based on the current solution, the third neighborhood structures S3 is used to search for better solutions than the current solution, and it means that the solutions found can dominate the current solution. 13. end for 14. If the stopping criteria are not satisfied, continue; otherwise, stop and output the best solution. 15. end for

The core of the VNS algorithm lies in the design of neighborhood structure set. In the production scheduling, the neighborhood structure of VNS can be obtained by exchanging the order of two jobs or inserting one job before another. This study designs three neighborhood structures, which are S1 , S2 , and S3 . The neighborhood solutions of S1 are generated as follows: select two jobs randomly and exchange their positions to generate a new neighborhood solution. The neighborhood solutions of S2 are generated as follows: select three jobs randomly and then disrupt their order to generate five new neighborhood solutions. The neighborhood solutions of S3 are generated as follows: select four jobs randomly and then disrupt their order to generate 23 new neighborhood solutions. The parameters M, M1, M2, and M3 affect the search range. A large value means a large search range, but at the same time, it reduces the operating efficiency of the algorithm. On the contrary, the operating efficiency of the algorithm will improve, but it means that the search range becomes smaller. In order to balance the two, it is reasonable to set their value within 10. 3.3. IMOEA/DTL Despite the outstanding global search capability of MOEA/DTL, it is likely to miss the locally better solution because MOEA/DTL does not search the neighborhood of the solution in detail in each iteration process. The MOEA/DTL is combined with VNS (IMOEA/DTL) to enhance its local search ability and performance. In IMOEA/DTL, the solution obtained in each iteration of MOEA/DTL is searched locally using the VNS algorithm to find a better solution. This study carries out VNS after the first update of EP, and VNS is carried out as Algorithm 3. Algorithm 3 Combination method of VNS and MOEA/DTL 1. for each i ∈ [1, 2, . . . , N ] do

2. nex_xi = V NS xi 3. end for 4. Output the new population.

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4. Case Study In order to demonstrate the feasibility of the energy-efﬁciency scheduling model under TOU electricity tariffs for tissue paper mills and the superiority of the proposed IMOEA/DTL, three popular multi-objective optimization algorithms, namely, MOEA/DMR [31], Non-dominated Sorting Genetic Algorithm II (NSGA-II), and Strength Pareto Evolutionary Algorithm 2 (SPEA2), are compared with the IMOEA/DTL in eight scheduling problems. The energy-saving potential of the IMOEA/DTL is evaluated by comparing IMOEA/DTL with workers in practice. The whole experiments are implemented in MATLAB 2015b. 4.1. Experiment Data The data are collected from a tissue paper mill in Guangdong, China. The data are collected from the Jiangmen branch of Vinda Paper (China) Co., Ltd., Jiangmen City, Guangdong Province, China. The data collection time is from 2017 to 2018. The scheduling data and product process data are mainly collected from the production scheduling department. These data come from the enterprise resource planning system. Machine data and energy consumption data are automatically collected by the manufacturing execution system. There are six production lines in the pulping and papermaking stage and seven production lines in the conversion stage. A total of 16 scheduling instances are generated randomly, the numbers and names of jobs in each scheduling problem are listed in Table 2. In each scheduling problem, the size of each job is generated randomly and obeys uniform distribution in the range of [10,000, 600,000]. In the tissue paper mill, the speed of the production line varies with the type of products, but each production line has a maximum speed. The maximum speeds in the pulping and papermaking stage and the conversion stage are shown as Table 3. Similarly, the power of each production line also varies with the product type. The maximum power of the pulping and papermaking stage and the conversion stage is shown Table 4. The setup energy consumption is dependent on the setup time and the setup power. In this study, the setup time of the pulping and papermaking stage and the conversion stage is randomly generated based on the real situation. The setup time of the pulping and papermaking stage shows uniform distribution in the range of [10, 100], while the setup time of the conversion stage shows uniform distribution in the range of [10, 60]. Table 5 lists the setup power of the pulping and papermaking stage and the conversion stage. The transportation energy consumption is related to the distance between production lines. The transportation energy consumption per unit product is shown in Table 6. Table 2. The name and number of jobs of 16 scheduling problems. Problems

Job Number

Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

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Table 3. The maximum speed of the production line in the pulping and papermaking stage and the converting stage. Pulping and Papermaking Stage

Speed (m/min)

Converting Stage

Speed (bag/min)

PL1 PL2 PL3 PL4 PL5 PL6

990 950 1010 970 1050 1110

BL1 BL2 BL3 BL4 BL5 BL6 BL7

260 320 330 325 335 360 400

Table 4. The maximum power of the production line in the pulping and papermaking stage and the converting stage. Pulping and Papermaking Stage

Power (kW)

Converting Stage

Power (kW)

PL1 PL2 PL3 PL4 PL5 PL6

1210 1280 1380 1470 1330 1490

BL1 BL2 BL3 BL4 BL5 BL6 BL7

130 145 148 120 138 135 137

Table 5. The setup power of the production line in the pulping and papermaking stage and the converting stage. Pulping and Papermaking Stage

Power (kW)

Converting Stage

Power (kW)

PL1 PL2 PL3 PL4 PL5 PL6

813 821 878 902 870 922

BL1 BL2 BL3 BL4 BL5 BL6 BL7

82 97 104 70 87 91 88

Table 6. The transportation energy consumptions per unit product (kW).

PL1 PL2 PL3 PL4 PL5 PL6

BL1

BL2

BL3

BL4

BL5

BL6

BL7

4 5 16 17 26 27

6 3 18 15 27 26

16 15 3 5 22 23

17 16 4 2 20 21

18 19 6 3 17 18

20 23 19 15 4 3

24 25 21 16 3 5

4.2. Performance Metrics The performance of the IMOEA/DTL, MOEA/D-MR, NSGA-II, and SPEA2 is evaluated using two metrics, which are Hypervolume indicator (HV-metric) and Set Coverage (C-metric). C-metric reﬂects the dominance between two non-dominated solution sets. A and B represent two non-dominated solutions, C ( A, B) can be deﬁned as the proportion of

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solutions in B that are dominated by at least one solution in A. The formulation of C ( A, B) is shown as follows. |{b ∈ B| a ∈ A : a b}| C ( A, B) = (28) | B| The C ( A, B) equal to one means that all solutions in B are dominated by some solutions in A. Meanwhile, C ( A, B) equal to zero means there is no solution in B dominated by the solutions in A. When C ( A, B) is greater than C ( B, A), then the quality of the solution A is better than that of B. The HV-metric of a non-dominated set can be represented by the size of portion of objective space that is dominated by those solutions collectively and bounded above by a reference point. The HV-metric can not only assess the proximity of the non-dominated set but also can assess the diversity of the non-dominated set. The HV-metric needs to be given a reference point, where we use the maximum value of the solutions obtained by all algorithms. When the HV-metric has a larger value, the approximate non-dominated solution set is better. Moreover, considering the randomness of the evolutionary algorithm, this study carries out the Wilcoxon signed-rank test to detect whether the results obtained by different algorithms are different significantly. The significance level is 0.05. A p-value of the Wilcoxon signed-rank test less than 0.05 indicates significant differences between the two algorithms. 4.3. Parameters Setting Table 7 summarizes the parameters of IMOEA/DTL, MOEA/D-MR, SPEA2, and NSGA-II. The population size and the maximum iterations are set as the same value to compare the performance of IMOEA/DTL, MOEA/D-MR, SPEA2, and NSGA-II. The parameters of NSGA-II, SPEA2, and MOEA/D-MR are set based on some literature and the trial and error method [31–35]. Moreover, considering the randomness of the evolutionary algorithm, three algorithms are run ten times for each scheduling problem, and the result is the average of ten times. Table 7. Parameters setting of MOEA/D-MR, Strength Pareto Evolutionary Algorithm 2 (SPEA2), Non-dominated Sorting Genetic Algorithm II (NSGA-II), and MOEA/DTL by Variable Neighborhood Search (IMOEA/DTL). MOEA/D-MR

N: 100 Mt: 100 F: 0.5 CR: 0.2 H: 99 Tm: 10 Tr: 10

SPEA2

N: 100 Size of archive: 100 Mt: 100 Pc: 0.8 Pm: 0.2

NSGA-II

IMOEA/DTL

N: 100 Mt: 100 Pc: 0.8 Pm: 0.2

N: 100 Mt: 100 Size of EP: 100 T: 10 Ps: 0.7 Pm: 0.3 Pc: 0.7 M: 5 M1: 10 M2: 5 M3: 3

4.4. Results and Discussion Table 8 describes the mean C-metric of the solutions obtained by IMOEA/DTL, MOEA/D-MR, SPEA2, and NSGA-II. W, X, Y, and Z represent the solutions obtained by MOEA/D-MR, NSGA-II, SPEA2, and IMOEA/DTL, respectively. From Table 8, it can be seen that C ( Z, W ) is larger than C (W, Z ), C ( Z, X ) is larger than C ( X, Z ), and C ( Z, Y ) is larger than C (Y, Z ) in 16 scheduling problems. The values of C ( Z, W ), C ( Z, X ) and C ( Z, Y ) are close to one in the eight scheduling problems. Meanwhile, the values of C (W, Z ), C ( X, Z ), and C (Y, Z ) are almost equal to zero. The C-metric indicates that other

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methods dominate the few solutions obtained by IMOEA/DTL. However, some solutions of IMOEA/DTL dominate all solutions obtained by MOEA/D-MR, NSGA-II, and SPEA2. As shown in Table 8, the solutions obtained by IMOEA/DTL have better performance than those obtained by MOEA/D-MR, NSGA-II, and SPEA2 in C-metric. Table 9 shows the p-value in the Wilcoxon signed-rank test of the C-metric between two algorithms. P1 represents the p-value of the Wilcoxon signed-rank test of the C-metric between IMOEA/DTL and MOEA/D-MR, P2 represents the p-value of the Wilcoxon signed-rank test of the C-metric between IMOEA/DTL and NSGA-II, and P3 represents the p-value of the Wilcoxon signed-rank test of the C-metric between IMOEA/DTL and SPEA2. P1, P2, and P3 are less than 0.05 in 16 scheduling problems, indicating signiﬁcant differences between IMOEA/DTL and MOEA/D-MR, IMOEA/DTL and NSGA-II, IMOEA/DTL and SPEA2. Tables 8 and 9 indicate that IMOEA/DTL is superior to MOEA/D-MR, NSGA-II, and SPEA2 in terms of C-metric. Table 8. C-metric of the solutions obtained by MOEA/D-MR, NSGA-II, SPEA2, and IMOEA/DTL. Problems

C(W,Z)

C(Z,W)

C(X,Z)

C(Z,X)

C(Y,Z)

C(Z,Y)

Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0.98 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 1 1 1 1 1 1 1 1 1 1 1 1 0.98 1 1

Table 9. The p-value of the Wilcoxon signed-rank test of the C-metric between two algorithms. Problems

Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020

Table 10 lists the average value of HV-metric of the solutions obtained by IMOEA/DTL, MOEA/D-MR, SPEA2, and NSGA-II. The solutions obtained by IMOEA/DTL have a larger average HV-metric than those obtained by MOEA/D-MR, SPEA2, and NSGA-II in all scheduling problems, indicating that the proximity and diversity of the solutions of

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IMOEA/DTL are best in all solutions. As shown in Table 10, the solutions obtained by MOEA/D-MR, NSGA-II, and SPEA2 are inferior to that obtained by IMOEA/DTL in terms of HV-metric. The p-value of the Wilcoxon signed-rank test of the HV-metric between two algorithms is shown in Table 11. P1 represents the p-value of the Wilcoxon signed-rank test of the HV-metric between IMOEA/DTL and MOEA/D-MR, P2 represents the p-value of the Wilcoxon signed-rank test of the HV-metric between IMOEA/DTL and NSGA-II, and P3 represents the p-value of the Wilcoxon signed-rank test of the HV-metric between IMOEA/DTL and SPEA2. P1, P2, and P3 are less than 0.05, demonstrating the signiﬁcant differences between IMOEA/DTL and MOEA/D-MR, IMOEA/DTL and NSGA-II, and IMOEA/DTL and SPEA2. Tables 10 and 11 indicate that IMOEA/DTL is superior to MOEA/D-MR, NSGA-II, and SPEA2 in terms of HV-metric. Table 10. Average values of hypervolume indicator (HV-metric) of the solutions obtained by MOEA/D-MR, NSGA-II, SPEA2, and IMOEA/DTL. Problems

MOEA/D-MR

NSGA-II

SPEA2

IMOEA/DTL

Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

3.46 × 1.75 × 107 7.02 × 107 5.33 × 107 3.33 × 107 3.40 × 107 4.22 × 107 2.40 × 107 5.99 × 107 2.66 × 107 4.41 × 107 4.43 × 107 5.43 × 107 3.32 × 107 4.83 × 107 8.19 × 107

3.32 × 1.65 × 107 6.38 × 107 5.04 × 107 3.06 × 107 3.53 × 107 3.74 × 107 2.01 × 107 5.44 × 107 2.62 × 107 4.49 × 107 4.07 × 107 5.43 × 107 3.27 × 107 4.54 × 107 7.78 × 107

3.42 × 1.58 × 107 6.60 × 107 5.15 × 107 3.09 × 107 3.37 × 107 4.03 × 107 2.07 × 107 5.75 × 107 2.60 × 107 4.45 × 107 4.18 × 107 5.46 × 107 3.35 × 107 4.62 × 107 8.15 × 107

5.43 × 107 2.79 × 107 9.82 × 107 8.27 × 107 4.92 × 107 5.87 × 107 6.29 × 107 3.65 × 107 8.79 × 107 4.32 × 107 7.30 × 107 6.58 × 107 8.77 × 107 5.16 × 107 7.67 × 107 1.19 × 107

107

Table 11. The p-value of the Wilcoxon signed-rank test of the HV-metric between two algorithms. Problems

Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020 0.0020

In order to intuitively show the scheduling schemes obtained by different algorithms, some Gantt charts of scheduling schemes obtained by different algorithms are provided, as shown in Figures 4–6. Each scheduling scheme corresponds to a solution in the Pareto front. We only provide Gantt charts of Job1, Job8, and Job16, and the Gantt charts for

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other scheduling problems are similar to these three. In the Gantt charts below, we can see how the jobs are organized and processed for the scheduling scheme obtained by each algorithm, and it can be seen that the scheduling scheme obtained by IMOEA/DTL has a smaller makespan. Not only that, in all the following scheduling schemes, IMOEA/DTL has the smallest energy cost.

(a)

(b) Figure 4. The Gantt charts of Job1, (a,b) are Gantt charts of the ﬁrst and second operation of Job1, respectively; the makespan and energy cost of NSGA-II, SPEA2, MOEA/D-MR, and IMOEA/DTL are (9.9020 × 103 , 8.1231 × 105 ), (9.8583 × 103 , 8.1278 × 105 ), (9.8063 × 103 , 8.1155 × 105 ), and (9.6900 × 103 , 8.1150 × 105 ) respectively.

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(a)

(b) Figure 5. The Gantt charts of Job8, (a,b) are Gantt charts of the ﬁrst and second operation of Job8 respectively; the makespan and energy cost of NSGA-II, SPEA2, MOEA/D-MR, and IMOEA/DTL are (2.3041 × 104 , 1.9083 × 106 ), (2.3147 × 104 , 1.9133 × 106 ), (2.3112 × 104 , 1.9117 × 106 ), and (2.3017 × 104 , 1.9041 × 106 ), respectively.

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(a)

(b) Figure 6. The Gantt charts of Job16, (a,b) are Gantt charts of the ﬁrst and second operation of Job16 respectively; the makespan and energy cost of NSGA-II, SPEA2, MOEA/D-MR, and IMOEA/DTL are (4.0066× 104 , 3.3994× 106 ), (4.0020× 104 , 3.3900× 106 ), (4.0029× 104 , 3.4038× 106 ), and (3.9960× 104 , 3.3800× 106 ) respectively.

Table 12 shows the average makespan and average energy cost obtained by MOEA/DMR, NSGA-II, SPEA2, and IMOEA/DTL. Table 12 indicates that both the average makespan and average energy cost obtained by IMOEA/DTL are lower than those obtained by MOEA/D-MR, NSGA-II, and SPEA2. Therefore, IMOEA/DTL can provide the solution with lower makespan and energy cost than MOEA/D-MR, NSGA-II, and SPEA2. This study adopts a multi-objective algorithm, and a non-dominated solution set is obtained. The solutions in the non-dominated solution set have lower energy cost or makespan, but they are mutually exclusive. Decision makers can select an optimal solution on the basis of actual situations. For instance, the solution with a low makespan can be selected in the case of a heavy production task, which can improve the utilization efﬁciency of the workshop and ensure that the task can be completed on schedule. On the contrary, the decision-makers can choose the optimal solution with low energy cost to reduce the production cost.

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Table 12. The average makespan and average energy cost obtained by MOEA/D-MR, NSGA-II, SPEA2, and IMOEA/DTL. Makespan (Minute)

Problems Job1 Job2 Job3 Job4 Job5 Job6 Job7 Job8 Job9 Job10 Job11 Job12 Job13 Job14 Job15 Job16

Energy Cost (CNY)

MOEA/D-MR

NSGA-II

SPEA2

IMOEA/DTL

MOEA/D-MR

NSGA-II

SPEA2

IMOEA/DTL

10,049 11,817 14,104 16,030 18,534 19,603 21,236 23,006 27,008 26,571 28,920 30,127 32,440 35,034 35,787 40,290

10,064 11,864 14,139 16,089 18,537 19,680 21,348 23,044 27,075 26,585 28,914 30,167 32,451 35,093 35,835 40,241

10,053 11,881 14,175 16,128 18,567 19,642 21,337 23,063 27,079 26,584 29,001 30,219 32,510 35,078 35,768 40,253

9939 11,800 14,033 16,008 18,460 19,531 21,222 22,953 26,922 26,501 28,886 30,117 32,358 34,972 35,712 40,185

801,309 964,677 1,158,100 1,302,626 1,520,818 1,610,892 1,777,566 1,916,511 2,223,799 2,193,870 2,427,444 2,565,900 2,699,366 2,887,249 2,984,084 3,380,449

803,965 966,456 1,161,747 1,304,014 1,521,966 1,608,901 1,779,676 1,921,468 2,226,399 2,193,213 2,426,101 2,568,756 2,700,491 2,887,706 2,985,389 3,385,432

804,358 966,000 1,159,518 1,303,485 1,521,371 1,610,826 1,778,261 1,918,722 2,224,613 2,193,967 2,424,184 2,566,343 2,697,074 2,886,665 2,985,440 3,383,498

795,656 957,500 1,150,038 1,291,973 1,511,605 1,596,377 1,768,963 1,908,951 2,213,336 2,183,339 2,408,955 2,551,189 2,684,005 2,876,694 2,971,161 3,368,202

In China, most of the scheduling jobs of the tissue paper mills are completed by workers based on their experience. The quality of the scheduling depends on the experience of the workers. In this study, a real scheduling problem is solved by IMOEA/DTL, and the solution is compared with that obtained by workers. The solution obtained by workers has the makespan of 17,035 and the energy cost of 1,368,497. Table 13 indicates that the average makespan obtained by IMOEA/DTL is about 7.5% less than that obtained by the worker. The average energy cost obtained by IMOEA/DTL is about 1.5% less than that obtained by the worker. From Table 13, it can be seen that the minimum energy cost is 1,333,494, and the corresponding makespan is 16,754, which reduces by 2.6% and 1.6%, respectively. The minimum makespan is 15,367, and the corresponding energy cost is 1,361,331, which decrease by 9.8% and 0.5%, respectively. The largest energy cost is 1,375,361, which is 0.5% higher than the cost obtained by the worker, but the corresponding makespan is reduced by 9.5%. The largest makespan is 18,675, which is 8.8% higher than the cost obtained by the worker, but the corresponding energy cost is reduced by 2.5%. It can be concluded that IMOEA/DTL can reduce both the energy cost and the makespan. Although the maximum makespan and the maximum energy cost are larger than those obtained by the worker, the corresponding energy cost and makespan are smaller. Figure 7 shows the scatter plot for the solutions obtained by IMOEA/DTL and the worker. The energy cost obtained by IMOEA/DTL is lower than that obtained by the worker. The solutions of IMOEA/DTL with lower energy cost than that obtained by the worker account for about 98.56% of the total solutions of IMOEA/DTL. While the solutions of IMOEA/DTL with lower makespan than that obtained by the worker account for about 97.12% of the total solutions of IMOEA/DTL. About 95.68% of the total solutions obtained by IMOEA/DTL have lower energy cost and makespan than those obtained by the worker. Table 13. The average, maximum, and minimum value of energy cost and makespan obtained by IMOEA/DTL. Average Makespan (Minute)

Average Energy cost (CNY)

Maximum Makespan (Minute)

Minimum Energy Cost (CNY)

Minimum Makespan (Minute)

Maximum Energy Cost (CNY)

15,754

1,347,737

18,675

1,333,494

15,367

1,375,361

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,02($'7/

:RUNHU

(QHUJ\ FRVW &1<

0DNHVSDQ PLQXWH Figure 7. The scatter plot for the solutions obtained by IMOEA/DTL and a worker.

In practical applications, the construction of basic data is a particularly critical issue, especially setup-related data, which requires a lot of statistical data. We suggest that a part of the key data can be constructed through the manufacturing execution system, and through the manufacturing execution system, we can know the status of machine, personnel, and materials in real time, and thus make timely responses to emergencies in the production process. In addition, we recommend using commercial production scheduling software and then integrating the model into commercial software. Compared with developing a scheduling system from scratch, this has a higher success rate. 5. Conclusions This study explored a novel energy-saving approach by scheduling under TOU electricity tariffs for tissue paper mills. First of all, an energy cost model was established based on TOU electricity tariffs. The energy cost consists of transportation energy cost, set-up energy cost, and processing energy cost. Second, an energy-efficiency scheduling model was built on the basis of the scheduling model and the energy cost model. Finally, the model was solved by proposing a novel IMOEA/DTL method. The experiment made a comparison between the proposed method and two popular multi-objective optimization methods, MOEA/D-MR, NSGA-II, and SPEA2. The experiment results demonstrate that the proposed method performs better than NSGA-II and SPEA2 in terms of C-metric and HV-metric. Moreover, the proposed method has been proven to have an energy-saving ratio of 2.6% through a real scheduling problem. Considering the similarity between the production processes in tissue paper mills and other papermaking mills, the results are of great reference significance for other papermaking mills. However, this study implemented the algorithms by MATLAB, and the speed of the algorithms should be further improved. Therefore, the speed of the algorithms will be improved in future research. Author Contributions: Conceptualization, Z.Z.; methodology, Z.Z.; software, X.C.; validation, Z.Z., X.C. and K.W.; formal analysis, Z.Z.; investigation, Z.Z., X.C., K.W.; resources, Z.Z.; data curation, Z.Z.; writing—original draft preparation, Z.Z.; writing—review and editing, Z.Z., X.C.; visualization, Z.Z.; supervision, Z.Z.; project administration, Z.Z.; funding acquisition, Z.Z, X.C. All authors have read and agreed to the published version of the manuscript. Funding: This work was supported by Natural Science Foundation of Guangdong Province (No. 2020A1515011468); Guangdong University Scientific Research Project (No.2019KTSCX189); Basic Public Research Project of Zhejiang Province (LQ18B060003).

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Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Most of the data is contained in the article or generated by the method suggested by the article. In addition to the real scheduling problem data, the data about the real scheduling problem are not publicly available due to the company’s requirements for data confidentiality. Conflicts of Interest: The authors declare no conflict of interest.

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Lignocellulosic Fibers from Renewable Resources Using Green Chemistry for a Circular Economy KHANDOKER S. SALEM, VED NAITHANI, HASAN JAMEEL, LUCIAN LUCIA, AND LOKENDRA PAL. The sustainable development of lignocellulose fibers exhibits significant potential to supplant synthetic polymer feedstocks and offers a global platform for generating sustainable packaging, bioplastics, sanitary towels, wipes, and related products. The current research explores the dynamics of fiber production from wood, non-wood, and agro-residues using carbonate hydrolysis and a mild kraft process without bleaching agents. With respect to carbonate hydrolysis, high yield, and good coarseness fibers are attained using a simple, low-cost, and ecofriendly process. Fibers produced using a mild kraft process have lower Klason lignin, carboxyl content, surface charges, and higher fiber length, and crystallinity. Eucalyptus fibers show the highest crystallinity while softwood carbonate fibers show the lowest crystallinity. Hemp hurd fibers contain the highest concentration of hard-to-remove water, and thus, suffer maximum flattening visualized by the microscopic images. The relatively high yield sustainable fibers with versatile properties can provide a significant economic benefit since fiber is the dominant cost for producing various bioproducts to meet society’s current and future needs. Contact information: Department of Forest Biomaterials, NC State University, Raleigh, NC 27695–8005, USA Global Challenges 2021, 5, 2000065 DOI: 10.1002/gch2.202000065 Creative Commons Attribution International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Article 2 – Pulping using Green Chemistry

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Lignocellulosic Fibers from Renewable Resources Using Green Chemistry for a Circular Economy Khandoker S. Salem, Ved Naithani, Hasan Jameel, Lucian Lucia, and Lokendra Pal* which are rich in forestry resources. But, in places where the availability of forest is limited, non-wood species and agro-industrial waste can be possible alternatives and equally valuable sources of biomass. However, the foremost challenge in producing sustainable lignocellulosic fibers is ensuring a sustainable source of biomass supply, since lignocellulosic resources are prima facie feedstocks for pulp, lignin, nanocrystals nanofibers, and biopolymers, which have versatile industrial applications, for example, paper products, bioplastics, biocomposites, biofuels, and bioenergy production, etc. Indeed, lignin has emerged as a potential sustainable bioresource for advanced applications due to high carbon content and renewable character.[5] Researchers have developed techniques to valorize lignin for applications in polymers and composites[6,7] and for producing sustainable thermo–electric materials based on carbon nanofibers (CNFs).[8,9] These CNFs have been successfully used as an alternative to carbon nanotubes (CNTs) to create high performance anodes for better thermo-mechanical and electrical properties.[10,11] However, to continue to increase its utilization, the circular economy is pivotal though it has been very difficult to efficiently recycle lignocellulosic fibers due to limitations in collection and its high degree of contamination. Thus, extensive research is being carried out to produce sustainable feedstock by introducing alternative pulping methods and/or alternative raw materials that would conserve the usage of chemicals, energy, and water.[12–14] Despite considerable research effort, wood is still the predominant resource for pulp production because it has been used to produce 89% of the world’s paper, whereas, only 11% is based on non-woody plants.[15] However, non-woody and agro-residues such as hemp hurds have been emerging as a viable resources to meet growing demand for economic and sustainable paper products.[16] Presently, hemp hurd has been used to meet 5% of the total global paper supply for tissue papers, bio-plastics etc., which has been made possible due to the valorization of the hemp hurd from its original use as animal bedding and hemp-lime construction materials.[16] The high cellulose content ≈ 50%–70%, quick harvesting time (4 months) and requirement of fewer harsh chemicals for processing, with respect to the hardwoods and softwoods, have made hemp hurd a promising candidate for sustainable lignocellulosic resource.[16] Another growing challenge for sustainable fiber sources is the introduction of an environment friendly, low chemical pulping

The sustainable development of lignocellulose fibers exhibits significant potential to supplant synthetic polymer feedstocks and offers a global platform for generating sustainable packaging, bioplastics, sanitary towels, wipes, and related products. The current research explores the dynamics of fiber production from wood, non-wood, and agro-residues using carbonate hydrolysis and a mild kraft process without bleaching agents. With respect to carbonate hydrolysis, high yield, and good coarseness fibers are attained using a simple, low-cost, and ecofriendly process. Fibers produced using a mild kraft process have lower Klason lignin, carboxyl content, surface charges, and higher fiber length, and crystallinity. Eucalyptus fibers show the highest crystallinity while softwood carbonate fibers show the lowest crystallinity. Hemp hurd fibers contain the highest concentration of hard-to-remove water, and thus, suffer maximum flattening visualized by the microscopic images. The relatively high yield sustainable fibers with versatile properties can provide a significant economic benefit since fiber is the dominant cost for producing various bioproducts to meet society’s current and future needs.

1. Introduction The world has been moving towards a sustainable, bio-based and circular economy due to social awareness and governmental regulations against single plastic use which could save up to $26 trillion by 2030.[1,2] Global environmental awareness has propelled the bio-based industries, like paper, tissue paper products, bioplastics, packaging, renewable lubricants, etc., more so than many other industries to play an important role in sustainable development because among their chief raw materials are renewable wood and non-wood ﬁbers.[3,4] Appropriate and sustainable utilization of bioresources are the major requirements to expand the bio-based economy to produce biochemicals, biofuels, bioplastics, and related products to their petroleum analogues. Wood has been a major source of biomass for the places K. S. Salem, Dr. V. Naithani, Prof. H. Jameel, Dr. L. Lucia, Dr. L. Pal Department of Forest Biomaterials NC State University Raleigh, NC 27695–8005, USA E-mail: lokendra_pal@ncsu.edu The ORCID identiﬁcation number(s) for the author(s) of this article can be found under https://doi.org/10.1002/gch2.202000065. © 2020 The Authors. Published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI: 10.1002/gch2.202000065

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Table 1. Chemical composition of feedstock. Cellulose [%]

Klason lignin [%]

Extractives [%]

Ash [%]

Eucalyptus

Raw material

46.7

27.9

4.3

1.3

19.8

Hemp hurds

43.0

24.4

2.2

1.4

29.0

Bamboo

43.2

26.7

2.2

0.8

27.1

Hardwood

44.6

26.9

3.7

1.1

23.7

Softwood

46.0

3.0

1.0

22.0

Hemicelluloses [%]

Constituent content calculated on a dry basis by subtracting sum of cellulose, lignin, extractives, and ash contents from 100%.

methods to raise pulp yield. Despite considerable research effort, kraft and soda are still the predominant processes for producing fibers with low lignin content suitable for papermaking.[17] Almost 80% of the total chemical pulping industry employees kraft pulping, which involves digestion of wood chips in a solution of sodium sulfide and sodium hydroxide at elevated temperatures and pressures.[18] It offers the benefit of recovering the cooking chemicals and heat, but also has some drawbacks including emissions of sodium and calcium salts particulates (flue gases) and volatilized reduced sulfur compounds.[19–24] In contrast to kraft, soda and organosolv are sulfur-free processes and thus alkali such as NaOH, KOH, and Ca(OH)2 are widely used as pretreatment steps for pulping.[25] They can be performed at ambient conditions, but require longer pretreatment times.[26,27] Alkali pretreatment is most effective for biomass having low lignin contents such as leftover lignocellulosic feedstocks, corn stover, switchgrass, bagasse, wheat, and rice straw.[28] Organosolv has been proposed based methanol, ethanol, acetic acid, acetone, etc., to remove lignin.[29] Although this technique comes with reduced emissions of sulfur dioxide and odorous gases because of the use of sulfur-free technology, it is not ready yet to be implemented on an industrial scale.[30] Thus, there is a great opportunity for an alternative pulping system to reduce ecological damage by minimizing waste in conventional pulping.[24] The current work discusses new types of chemical pulping where significant efforts have been made to attain sustainable utilization of natural resources. The new processes were carried out using very mild chemical conditions and resulted in higher yield of pulp compared to conventional methods (34%– 55%).[31] Non-conventional pulping using 4% sodium carbonate based on Na2O for carbonate hydrolysis and 12% active alkali (NaOH + Na2S, based on Na2O) for mild kraft were studied for five feedstocks: eucalyptus, hemp hurd, bamboo, hardwood and softwood. Fiber yield, lignin content, brightness, surface charges, hard to remove water, and crystallinity were determined. Hence, the present work demonstrates how carbonate hydrolysis and mild kraft pulping can produce higher value fibers. This study will enable acceleration of the biorefinery to tune the properties different feedstock fibers.

the Netherlands and Bamboo (Henon) supplied by National Bamboo, LLC. Raleigh, NC, Southern pine, eucalyptus (E. grandis), and mixed hardwood and softwoods from local mills. The chemical compositions of these ﬁbers were determined according to the guidance of U.S. Department of Energy, National Renewable Energy Laboratory (NREL) analytical procedure TP-510-42618 or the ASTM E1758-01 (2015) in agreement with previous studies[32,33] presented in Table 1. All chemical reagents were purchased from Fisher Scientiﬁc.

2.2. Methods 2.2.1. Defibration Laboratory defibration highlighting the features of sodium carbonate and mild kraft defibration are shown in Figure 1. The defibration process conditions are in Table 2. A higher water-tosolids ratio of 8:1 was used for hemp due to its low bulk density compared to hardwood. The carbonate hydrolysis was carried out using 4% carbonate (based on Na2O). Kraft pulping was done using 12% active alkali and 25% sulfidity (NaOH+Na2S) (all on an Na2O basis). Both processes were conducted in a stainless-steel reactor under controlled temperature (160 °C) for 3 h using a mild concentration of sodium carbonate (carbonate) and a high concentration of alkali charge (kraft), respectively. The pulp was washed and refined on the laboratory disc refiner (The Bauer Bros Co., Springfield, Ohio, Model 148-2, rpm 3600) at disc gaps of (0.2– 0.1–0.05) mm with three passes for hard wood pulp and disc gaps of (0.1–0.05) mm with two passes for hemp pulp before screening on a 0.15 mm slotted laboratory screen. Pulp yield, Klason lignin content, and freeness were determined using the TAPPI T222 and TAPPI T227 om-09 standard methods, respectively. For simplicity, the following sample IDs will be mentioned in the later part of the article: EU_C and EU_K (Eucalyptus fiber produced by Carbonate and Kraft process); HM_C and HM_K (Hemp fiber produced by Carbonate and Kraft process); BMB_C and BMB_K (Bamboo fiber produced by Carbonate and Kraft process); HW_C and HW_K (Hardwood fiber produced by Carbonate and Kraft process) and SW_C and SW_K (Softwood fiber produced by Carbonate and Kraft process)

2. Experimental Section 2.1. Materials

2.2.2. Characterization of Diﬀerent Fibers

Five types of feed stocks were selected: Futura 75 cultivar hemp hurds, dew retted, and decorticated procured from

Fiber Quality Analysis: Fiber length (lw), ﬁne contents and other physical properties of the diﬀerent samples were determined

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Figure 1. The pulping scheme for diﬀerent feed stocks and subsequent processing of ﬁbers.

by using a high-resolution fiber quality analyzer: HiRes FQA, OpTest Equipment Inc, Hawkesbury, ON, Canada. Before testing, fiber quality analysis (FQA) was calibrated and used according to the manufacturers’ specifications. The whole pulp for each sample was taken and disintegrated before the measurement was done. Fourier Transform Infrared Spectroscopy (FTIR): Fourier transform infrared (FTIR) spectra of the different fibers were recorded using a PerkinElmer Spectrum One FTIR spectrometer. For each sample, the diamond crystal of an attenuated total reflectance (ATR) accessory was brought into contact with the area to be analyzed. The contact area was a circle of about 1.5 mm in diameter. All spectra were recorded between 4000 and 500 cm−1 with a resolution of 4 cm−1 with 32 scans per sample. For comparison, spectra were adjusted to the same baseline. Brightness Measurement: The brightness of the fibers was measured by following the ISO 2470 standard method using the color spectrophotometer Color Touch X, Technidyne, Indiana, USA. This procedure was repeated for ten samples for each of the fibers, and the mean value was taken. Total Carboxyl Content Analysis: Acid-base titration was used to determine the total carboxyl content of the pulps.[34,35] 100 mg of pulp was dissolved in 20 mL 0.1 n NaOH and stirred with a magnetic stirrer for 2 h. An excess amount of 0.1 n NaOH was titrated with 0.1 n HCl using phenolphthalein as an indicator.

The carboxyl content in milliequivalents per 100 g of the pulp slurry was calculated as: Carboxyl content = (Vb − Va ) × N × 100/W

(1)

Where, N is the normality of HCl (Equation (l)), Vb and Va are the volumes of HCl in absence and presence of sample, and W is the weight of sample (g). Charge Determination: Charge estimation on the fibers was carried out using the colloidal titration method.[36] The fiber samples were disintegrated into pulp at a 0.075% consistency (mass of solids relative to total mass + water) in deionized water. The colloidal charge of 200 mL of the resulting pulp suspension was evaluated by titration using a CHEMTRAC ECA 2000 P streaming current analyzer. The charge neutralization points of fibers were determined by the addition of cationic polymers (poly(diallyldimethylammonium chloride) (polyDADMAC)) to the suspension. Hard-to-Remove Water Measurement: Hard to remove (HR) water was determined using TGA.[37] The sample was taken in platinum sample pans. The temperature was then raised to 110 °C from 30 °C at 10 °C min−1. Drying experiments were run isothermally at 110 °C for 15 min until no more drying occurred. The non-freezing bound water was calculated by subtracting the total freezable water from the moisture ratio in the

Table 2. Process condition.

Process Carbonate hydrolysis

Feedstock

Water–solid ratio

Pulping chemicals

Hemp

11.2

4% sodium carbonate based on Na2Oa)

Eucalyptus, bamboo, hardwood, softwood

11.3

4% sodium carbonate based on Na2O

Hemp

12.8

12% active alkali 25% sulﬁdity (NaOH+Na2S) based on Na2O

Eucalyptus, bamboo, hardwood, softwood

13.3

12% active alkali 25% sulﬁdity (NaOH + Na2S) based on Na2O

Mild kraft

Reporting on a Na2O basis indicates the actual chemical relationship between the pulping chemicals used. It is a standardized way of normalizing the concentration strengths (based on Na2O).

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Figure 2. FTIR spectra of diﬀerent ﬁbers prepared by A) Carbonate Hydrolysis and B) Mild Kraft.

sample determined gravimetrically using a TGA microbalance (110 °C until weight did not change). X-Ray Diffraction (XRD) Analysis: A Rigaku SmartLab X-Ray Diffractometer, operated at 45 kV and 40 mA with a Ni-filtered CuK radiation, was used to determine the crystallinity index of the samples. X-ray diffractograms were recorded at 0.02° s-1 over a 2 scan in the range 5°–60°. Segal Peak height method was used to calculate the crystallinity index (CI) of the samples using the following equation: Crystallinity Index ( CI) = (I 002 − I AM ) × 100/I 002

(2)

Scanning Electron Microscopy (SEM): Handsheets of the different ﬁbers produced using carbonate and mild kraft pulping process were made at a target basis weight of ≈40 g m−2 as per the TAPPI T205 method with a light weight (≈0.15 kg) foam roller instead of a standard heavy (13 kg) brass roller, without any pressing, and dried twice on a drum dryer at 220°F. The morphological characterization of samples was carried out using Hitachi S3200N variable pressure scanning electron microscope (VPSEM). Samples were sputter coated with AuPd coating for 10 minutes and images were taken at 10kV.

3. Results and Discussions 3.1. Fourier Transform Infra-Red Spectroscopic Analysis The chemical structure of the different fibers prepared by carbonate hydrolysis and kraft process were compared in Figure 2 to examine the effect of different pulping on the fiber structures. The appearance of peak in the region of 1030–1170 cm−1 is due to COC and CO stretch of primary and secondary hydroxide groups of the carbohydrates and hydroxyphenyl, guaiacyl, and syringyl groups of lignin.[38] The peaks at 1281, 1370, and 1427 cm−1 may be due to aromatic esters, ether, and

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phenol compounds.[39] The peak corresponding to 1730 cm−1 is from unconjugated CO stretching which is due to vibration of aliphatic carboxylic acids and ketones of hemicellulose or lignin groups and that near 1650 cm−1 is due to conjugated carbonyl found in hemicellulose and lignin groups.[40] Moreover, CH symmetric and asymmetric stretching bands appeared at 2900 cm−1 and hydrogen bonded stretching bands of OH groups at 3400 cm−1 are characteristics peaks of hydroxyl groups of cellulose.[39] All the fibers, including the hemp hurds, had similar FTIR spectra since they had similar lignocellulosic compositions as shown in Table 1 and none of the pulping resulted in significant change in the chemical structure of the fibers.

3.2. Pulp Yield The yield of the carbonate and kraft pulps (total pulp wt% obtained after defibration) were calculated and found to vary from 49%–75% depending on the source of fibers and pulping, which were comparatively higher than the pulp yield produced by conventional methods as shown in Figure 3A. The yield of carbonate hemp pulps was 71.3%, which was slightly less than the carbonate eucalyptus and bamboo, but almost the same as carbonate hardwood and softwood pulps. However, the yield of mild kraft hemp was similar to eucalyptus but higher than the other kraft pulps. This might be due to the morphology of the hemp hurds allowing easier penetration of pulping chemicals compared to hardwood and softwood.[16] The pulp yield was higher for the carbonate than the kraft for all the fiber types because carbonate was operated at lower pH. Higher pH resulted in higher hydroxyl concentration which controls the intensity of fiber defibration and consequently causes random chain scission in cellulose and hemicelluloses. This promotes peeling and results in lower pulp yield because the pulp defibration rate is proportional to the OH concentration.[16,41,42] Thus, kraft pulping facilitated removal of higher

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Figure 3. Graphical representation of A) Total yield and B) Klason lignin content of different fibers produced using two different methods.

fines showed an opposite trend, that is, decreased when compared with the fibers produced by carbonate. The production of longer fiber and lower fines during kraft can be attributed to higher pH. Higher pH resulted in longer fibers, lower coarseness, and lower fines by removing more hemicelluloses, lignin, and extractives as reported earlier.[16,43] Studies of fiber properties have shown that the fiber strength increases with increases in fiber length and decrease in coarseness. Longer fibers have more fiber joints and a higher area for bonding and therefore create a stronger network compared to shorter fibers. On the other hand, thinner fibers collapse more easily than a coarser fiber with thicker cell walls. The collapsed fibers will create a network with much higher density and lower bulk. The flexibility of the fibers and the number of fiber joints will therefore increase the tensile strength. The uncollapsed fibers will create a network with higher porosity and higher bulk compared with the collapsed ones.[44] Thus, fibers produced in kraft will form stronger sheets and possess better tensile properties.[45] However, fiber curliness negatively affects tensile and tensile

amounts of lignin at high pH as shown in Figure 3B and supported by FTIR (Figure 2B). The peaks corresponding to 1730 and 1650 cm−1 arise from lignin functional groups from carbonate which is less visible in mild kraft because lignin content is relatively low in the latter. Thus, carbonate hydrolysis and mild kraft produced pulps with diﬀerent yields, lignin percentages, and diﬀerent compositions.

3.3. Fiber Morphology The fiber structure was further investigated by comparing the fiber morphology of the pulps produced by the two processes. Fiber morphology is related to fiber structure, which is primarily regulated by feedstock and pulping. Generally, fiber length, coarseness, kink, curl and fines are used to describe fiber morphology. Table 3 provides data on the morphology of fibers. The length of all the fibers produced by kraft pulping increased; but the other properties: coarseness, kink, curl, and Table 3. Physical Properties of Different fibers. Fiber length Lw, [mm]

Coarseness [mg m−1]

Curl index

Kink index [1 mm−1]

Fines [%]

EU_C

1.06

0.20

0.05

0.67

2.29

10.9

EU_K

1.09

0.08

0.05

0.08

2.12

22.5

HM_C

0.69

0.18

0.07

1.27

7.30

15.7

HM_K

0.77

0.07

0.05

0.08

3.93

23.4

BMB_C

1.22

0.36

0.07

0.80

17.73

10.9

BMB_K

1.41

0.11

0.06

0.62

15.09

23.3

HW_C

0.8

0.20

0.08

0.84

5.81

12.7

HW_K

1.17

0.10

0.05

0.62

2.33

19.7

SW_C

1.94

0.45

0.06

0.65

4.29

12.6

SW_K

2.45

0.27

0.05

0.55

1.25

13.2

Sample ID

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Brightness ISO

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stiffness indices, while it increases tear and fracture toughness indices.[46] The curl index gives the maximum elongation of the fiber up to breakage, which indicates the stability of the paper web in the open draw. The deformed fibers contribute uneven distribution of stress along the length of a curled fiber in a fracture zone, transferring more stresses to the bonds, which increases the tear strength of the sheets. Thus, fibers produced by carbonate form sheets having lower tensile strength, but higher tear strength. The fiber curl, in addition, increases the bulk and porosity of the pulp sheet but decreases the drainage resistance.[46] Curly fibers cause more scattered reflection of light, which results in a matte appearance and opacity. Thus, fibers produced by carbonate have higher coarseness and lower brightness than kraft. The presence of lower lignin content in kraft also affected the brightness. Thus, carbonate pulps with higher coarseness, curl index and fines could be used to make paper or tissue products with high bulk and tear strength, whereas, kraft pulp generates longer, brighter fibers to give stronger, flexible and brighter paper products.

3.4. Carboxyl Content and Surface Charge In addition to the above mentioned properties, the charge on fibers is a well-known parameter in papermaking and plays a vital role in their performance through electronic interactions of the charged soluble and particulate fractions.[43] The electrical charges at the surfaces of the cellulose fibers are a significant parameter strongly affecting the swelling ability of cellulose fibers and provides a driving force for adsorption of retention aids, sizing agents, and strength enhancing chemicals.[47] Fiber charge is a significant characteristic of cellulose fibers, which strongly affects post-processing such as enzymatic modification.[48] The carboxyl content and surface charge of different fibers are shown in Figure 4. The carbonate pulps have relatively higher carboxyl content and surface charge than kraft. The carboxyl content of the fibers is formed due to con-

Figure 4. Carboxyl content and surface charge of different fibers produced using two different methods.

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version of the 4-O-methylglucuronic acid side groups (MeGlcA) of xylan to hexenuronic acids (HexA) by elimination of the 4-Omethoxyl group and deprotonation during peeling at alkaline conditions.[47] The carboxyl content of hemp pulp produced by carbonate was similar compared to carbonate hardwood pulp, but lower than the other carbonate pulps. However, the kraft hemp pulp contained almost similar carboxyl content like eucalyptus and hardwood but lower than the bamboo and softwood pulps produced by mild kraft. The lower carboxyl content of the kraft pulp is due to higher alkaline conditions at which the pulping was carried out which decreased reprecipitation of lignin and hemicellulose onto the surface of the fibers.[47] The relatively higher surface charge of the carbonate pulps was due to its high anionic charge density contributed by resins, fatty acids, carboxylic acid groups of the hemicelluloses, and lignin’s phenolic groups.[49] The hydrophilic carboxyl group in the fiber interacts with water and enables fibers to absorb more water to increase swelling capacity, important for the tissue paper industry.[50] The presence of greater numbers of carboxyl groups and surface charge in the fiber facilitates better entanglement by inducing hydrogen bonding to increase the tensile and burst properties of the fibers.[44,51] The carboxyl groups act as binding sites and also enables controlled chemical loading and release by regulating the interactions between the carboxyl group and chemicals.[34,35] Thus, tissue, towels and wipes with varying surface charge and carboxyl content can be produced by using different fiber types or pulping (Figure 4).

3.5. Crystallinity Indices The effect of the carbonate and mild kraft pulping on the crystalline structure was evaluated further to study the changes in crystallinity index of different fibers. It was found that the crystallinity indices of the kraft fibers were higher than that of carbonate fibers as shown in Figure 5. The amorphous nature

Figure 5. The Crystallinity Index of different fibers produced using two different methods.

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of the fiber is imparted by the hemicelluloses which is a short, linear and highly branched chain of sugars and possesses shorter side chains.[52] Thus, they induce a branched network through extensive crosslinking to lignin and cellulose by cinnamate acid ester linkages and hydrogen, respectively.[53] The kraft fibers has higher crystallinity since the process was operated at higher pH which facilitated dissolution of a higher level of amorphous cellulose. pH range at which carbonate ruptured the structural linkages between lignin and other carbohydrate fractions in the lignocellulosic biomass, but could not remove lignin as much as kraft.[54,55] As a result, the carbonate treatment of the fibers resulted in a carbohydrate heterogeneous matrix with lower crystallinity compared to kraft and a lower degree of polymerization.[47]

3.6. Hard-to-Remove Water The Hard-to-Remove water is defined as trapped water, freezing bound water, and non-freezing bound water which requires a higher energy for drying.[37] It is an important parameter as it affects the different properties of the paper products like water absorption, tensile, drying energy, and the reactivity cellulose towards chemicals.[37,44,56] Thus, the effect of the different pulping processes on the HR water content of the different feedstocks were investigated graphically represented in Figure 6. It can be observed form Figure 6 that the hemp fiber produced using carbonate and mild kraft contained the highest levels of HR water compared to other fibers, whereas the carbonate and kraft softwood fibers contained the least amount of HR water. The hemp fiber had higher HR water than the others since it has a much higher hemicellulose content. Hemicellulose is amorphous in nature and allows more water penetration which facilitates more fiber-water interaction increasing the HR water content.[52,56] The presence of relatively higher lignin content in softwood reduces the HR water content as lignin being hydrophobic diminishes fiber-water interactions.[57] However, HR water content was higher for fibers produced

using kraft (Figure 6). The carbonate fibers, though they have less crystallinity, are associated with less HR water. This might be due to the presence of higher lignin content which limits the ability of water molecules to form hydrogen bonds with the hydroxyls of the cellulose.[58] On the contrary, kraft fibers have relatively much less lignin content which allows the cellulosic hydroxyls to interact with the water forming hydrogen bonds and increasing HR water content. Thus, kraft fibers would collapse more as shown in Figure 7 because the HR water regulates extent of fiber collapsing. The reactivity of the kraft fibers will be negatively affected as well, since HR water hinders the facile diffusion of chemical reagents by forming a hydration barrier which limits accessibility to the hydroxyl groups and reduces the reaction kinetics.[56] Thus, lower HR content of the carbonate fibers indicates that they will suffer less hornification than kraft fibers, supported by the coarseness data of the fibers as shown in Table 3 and SEM images in Figure 7.

3.7. Scanning Electron Microscopic Image Analysis SEM image analysis was done to visualize the effect of carbonate and mild kraft on fiber morphology. It can be observed form the images of the different fibers that the handsheets made from kraft suffer greater flattening than carbonate (Figure 7). These results directly relate to the coarseness and HR water of the fibers. Higher bulk of carbonate handsheets can be attributed to higher coarseness of the pulps produced by carbonate. Thus, kraft hemp pulp having the least coarseness (Table 3) yielded sheets with the least thickness (Figure 7B), whereas, the carbonate softwood showed highest thickness owing to its highest coarseness. The kraft fibers exhibited higher HR water and as HR water leaves during drying, more hydroxyls of cellulose become available for bonding. These hydroxyls interact with each other forming hydrogen bonds which leads to irreversible flattening of the fibers resulting in higher flattening of the fibers.[56] Therefore, hemp fibers suffered the highest flattening due to its least coarseness (Table 3) and highest HR water value (Figure 6).

4. Conclusions

Figure 6. Hard to remove water content of diﬀerent ﬁbers.

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This study reports production of pulp from several fiber feedstocks after sodium carbonate and mild kraft pulping processes. The pulp yield was higher for sodium carbonate, which is a significant economic benefit because fiber is the dominant cost for producing paper products. The high yield of hemp fibers using both pulping processes and its low coarseness, low fines, and high brightness value qualify it an emerging potential resource for paper and tissue paper industries because it improves tensile, burst resistance, and softness of tissue handsheets. The lignin content was lower for pulp produced using mild kraft because it removes more lignin, which results in decreased coarseness. Higher coarseness and lower HR water content using carbonate led to less fiber collapsing, very useful for maintaining higher bulk for tissue paper products which has a direct correlation with water absorbency and bulk

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Figure 7. SEM images of diﬀerent ﬁbers produced using A) Carbonate Hydrolysis and B) Mild Kraft techniques.

softness. Moreover, a lower HR water content of carbonate also facilitates chemical treatment of the pulp at much less chemical consumption compared to kraft because the HR water acts

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as a barrier for chemical modiﬁcation. The kraft pulps, on the other hand, have longer ﬁbers, lower curl and kink index, and higher brightness, important for producing strong sheets. The

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carbonate pulps possessed higher carboxyl and surface charge which increases water uptake, a very important requirement for paper towels. Thus, carboxyl content can be controlled using different pulping methods and fiber types, which can be manipulated to control the binding capacity of the fibers and have potential use in antimicrobial tissue wipes.

Acknowledgements The work was carried out in the Department of Forest Biomaterials at NC State University. This work was performed in part at the Analytical Instrumentation Facility (AIF) at NC State University, which is supported by the State of North Carolina and the National Science Foundation (Award Number ECCS-1542015).

Conﬂict of Interest The authors declare no conﬂict of interest.

Keywords bamboo, carbonate hydrolysis, green chemistry, hemp, high-kappa kraft pulping, sustainable ﬁbers Received: July 29, 2020 Revised: September 8, 2020 Published online: November 4, 2020

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Gel Point as Measurement of Dispersion Degree of Nano-Cellulose Suspensions and Its Application in Papermaking JOSE LUIS SANCHEZ-SALVADOR, ANA BALEA, CARLOS NEGRO, MARIA CONCEPCION MONTE & ANGELES BLANCO. The dispersion degree of cellulose micro and nanofibrils (CMFs/CNFs) in water suspensions is key to understand and optimize their effectiveness in several applications. In this study, we proposed a method, based on gel point (Øg), to calculate both aspect ratio and dispersion degree. This methodology was validated through the morphological characterization of CMFs/CNFs by Transmission Electronic Microscopy. The influence of dispersion degree on the reinforcement of recycled cardboard has also been evaluated by stirring CMF/CNF suspensions at different speeds. Results show that as stirring speed increases, Øg decreased to a minimum value, in which the aspect ratio is maximum. Then, Øg increased again. Suspensions with lower Øg, in the intermediate region of agitation present very good dispersion behavior with an open and spongy network structure, in which nanofibril clusters are totally dispersed. Higher stirring speeds shorten the nanofibrils and the networks collapse. Results show that the dispersion of the nanocellulose at the minimum Øg before their addition to the pulp, produces higher mechanical properties, even higher than when CNFs and pulp are agitated together. This method allows for the determination of the CMF/CNF dispersion, to maximize their behavior as strength agents. This knowledge would be crucial to understand why some industrial trials did not give satisfactory results. Contact information: Chemical Engineering and Materials Department, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain. Nanomaterials 2022, 12, 790. https://doi.org/10.3390/nano12050790 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Article 3 – Nanocellulose & Papermaking

nanomaterials Article

Gel Point as Measurement of Dispersion Degree of Nano-Cellulose Suspensions and Its Application in Papermaking Jose Luis Sanchez-Salvador

, Ana Balea

, Carlos Negro

, Maria Concepcion Monte

and Angeles Blanco *

Chemical Engineering and Materials Department, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain; josanc03@ucm.es (J.L.S.-S.); anabalea@ucm.es (A.B.); cnegro@ucm.es (C.N.); cmonte@ucm.es (M.C.M.) * Correspondence: ablanco@ucm.es; Tel.: +34-91-394-42-47

Citation: Sanchez-Salvador, J.L.; Balea, A.; Negro, C.; Monte, M.C.; Blanco, A. Gel Point as Measurement of Dispersion Degree of

Abstract: The dispersion degree of cellulose micro and nanofibrils (CMFs/CNFs) in water suspensions is key to understand and optimize their effectiveness in several applications. In this study, we proposed a method, based on gel point (Øg ), to calculate both aspect ratio and dispersion degree. This methodology was validated through the morphological characterization of CMFs/CNFs by Transmission Electronic Microscopy. The influence of dispersion degree on the reinforcement of recycled cardboard has also been evaluated by stirring CMF/CNF suspensions at different speeds. Results show that as stirring speed increases, Øg decreased to a minimum value, in which the aspect ratio is maximum. Then, Øg increased again. Suspensions with lower Øg , in the intermediate region of agitation present very good dispersion behavior with an open and spongy network structure, in which nanofibril clusters are totally dispersed. Higher stirring speeds shorten the nanofibrils and the networks collapse. Results show that the dispersion of the nanocellulose at the minimum Øg before their addition to the pulp, produces higher mechanical properties, even higher than when CNFs and pulp are agitated together. This method allows for the determination of the CMF/CNF dispersion, to maximize their behavior as strength agents. This knowledge would be crucial to understand why some industrial trials did not give satisfactory results.

Nano-Cellulose Suspensions and Its Application in Papermaking. Nanomaterials 2022, 12, 790. https://

Keywords: nanocellulose; dispersion degree; gel point; cellulose nanofibers; aspect ratio; papermaking; mechanical properties

doi.org/10.3390/nano12050790 Academic Editors: Giuseppe Lazzara and Rushdan Ahmad Ilyas Received: 30 December 2021 Accepted: 22 February 2022 Published: 26 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁliations.

Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

1. Introduction Several effective methods have been applied to disintegrate cellulose fibers into substructures with micro-or nano-size dimensions as cellulose micro/nanofibrils (CMFs/CNFs) or micro/nanocrystals [1–4]. Among them, the use of CMFs/CNFs has gained attention due to their high surface area, high strength, or their excellent barrier properties [5–8]. CMF/CNF applications have been thoroughly studied in several fields such as papermaking [9–11], food packaging [12,13], anti-microbial films [14], biomedical applications [15–17], wastewater treatments [18,19], or cement-based materials [20]. However, although their effect has been highly successful at lab scale, these data are not always replicable. This is the case of the reinforcement of recycled cardboard for packaging, where improvements above 60% in the Tensile Index has been achieved at lab scale using 3% of CNF prepared from the same raw material, pretreated with 10 mmol/g of NaClO in TEMPO-mediated oxidation and then homogenized [10,11]. However, the uncertainty of pilot trials has limited the industrial application, especially when nanocellulose was not produced on-site [21,22]. This fact is still not fully understood. CMF/CNF gels production has been widely studied during the last decade; nevertheless, their characterization is an area still under development. Many parameters have been developed to characterize CMFs/CNFs in terms of morphology, rheological properties, composition, carboxyl or aldehyde content, nanoﬁbrillation degree, etc. [2,5,23,24].

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CMFs/CNFs have been tested in strength and coating applications, failing without any apparent reason. This suggests that some key parameters are not taken into consideration as, for example, the dispersion degree of nanofibrils before its application or the mixing of CNFs within the studied matrix [25]. Some researchers have studied the importance of dispersion and uniformity of nanocellulose on the reinforcement performance, e.g., in paper [26] or in polymeric matrices [27]. Although several methods for measuring distribution size or homogeneity, such as dynamic light scattering, turbidity, self-assembly, and shear birefringence have been reported [23], there are currently no methodologies for determining dispersion degree on the CMF/CNF suspensions despite being an important parameter for the use of nanocelluloses at industrial scale [21]. Our hypothesis is that the stirring methods used to prepare the CMF/CNF suspensions may have an impact on the entanglement network affecting the aspect ratio (AR) of CMFs/CNFs as well as the separation between the nanofibers and, therefore, their final behavior. AR determination is based on several sedimentation methodologies: on the one hand, the use of the gel point or connectivity threshold (Øg ) [28] and, on the other hand, the use of the differences in light transmission with time due to sedimentation [29]. In this study, the Øg method is proposed to study the dispersion of CMF/CNF suspensions and validated by the morphological characterization of the CMFs/CNFs using Transmission Electronic Microscopy (TEM) images to determine both the CMF/CNF structure and the mean diameter of the nanofibrils. Øg describes the compressibility and structure of sediments and is defined as the volume concentration of a suspension in the boundary between semi-dilute and dilute region which depends on time [6,28]. This volume fraction is also considered the lowest volume fraction, at which all primary fibres and fibre flocs are interconnected throughout the container, forming a self-supporting three-dimensional network. Below the Øg concentration, the material suspended does not contribute to the mechanical strength of the suspension [30]. Figure 1 shows the progress with time in a sedimentation experiment. During the experiment, the volume fraction on the top of the sediment is considered to be unchanged from Co and, above this fraction, a clear liquid region appears [31]. As time passes, a concentrated deposit is formed in the lower part of the measured cylinder, whose volume becomes constant with time.

Figure 1. Progression of a self-supporting region with time.

Where Co is the initial concentration of solids, and Hs /Ho is the relation between the sediment height and the initial suspension height.

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In order to adapt the Øg methodology to CNFs, it was necessary to use a dye to visualize the sedimentation line of nanofibers. Cristal violet was selected since it did not influence the sedimentation of the samples. Results showed that highly fibrillated CNFs presented sedimentation curves different from the conventional ones, requiring longer sedimentation times to obtain stable deposits than other cellulosic materials, as previously published [32]. To determine Øg values, at least five sedimentation experiments with different Co are required. The curve that relates the Co against the Hs /Ho is plotted. Then, the derivative of the curve close to zero allows the determination of Øg as Equation (1) shows, in which Øg and Co have the same units [31,33–35].). Two mathematical methods have been traditionally used to calculate Equation (1). The first one is the fitting to a quadratic equation without an independent term in which Øg is the first order coefficient [32,36,37], and the other is using the fitting tool CSAPS in MATLAB [28,38]. Both are tedious and time-consuming. Recently, a simplification of the Øg methodology (Equation (2)) allows to reduce the experiments labor by at least 60%, using only one measured cylinder or two if the Co selected is not suitable, showing an error lower than 7% in Øg values and 3% in the calculation of the estimated AR [39]. ⎞ ⎛ dCo ∅g = lim ⎝ ⎠ Hs Hs d Ho Ho →0

∅g(est) =

(1)

Co (i) − Co (0) Co ( i ) − 0 Co (i) = = (Hs/Ho (i)) − (Hs/Ho (0)) (Hs/Ho (i)) − 0 (Hs/Ho(i))

(2)

To estimate AR from Øg , the Effective Medium Theory (EMT) and the Crowding Number (CN) theory [36,37] are two possible alternatives. EMT was firstly developed by Celzard et al. [40] to describe the conductivity of a material in which the particles are dispersed, for example, for spheroid graphene particles dispersed in air. AR and Øg are related by the Equations (3) and (4), according to Celzard et al. and Varanasi et al. [37,40]. 9Lc (1 − LC ) vol.% ∅g = (3) vol.% 2 + Lc (15 − 9Lc ) AR−2 1 + 1 − AR−2 ln (4) Lc = − 2 1 − AR−2 3 −2 −2 1 − 1 − AR 2 1 − AR where Lc is the depolarization factor of the particles. Kerekes and Schell [41] developed the CN theory that relates the Øg and the AR of the cellulose fibers. Then, Øg was estimated by Martinez et al. [35] with a CN value of 16 ± 4, based on the analysis of positron emission tomography (PET) measurements of dilute fiber sedimentation experiments. This fact establishes a relationship between Øg and AR in Equation (5): vol.% ∅g = 24/AR2 (5) vol.% However, the volume fraction is more difficult to measure than the solid fraction, Øg (kg fiber/ kg suspension) as Varanasi et al. [37] have demonstrated. Therefore, the relation between Øg (vol./vol.) and Øg (wt.%/wt.%) may be expressed by Equation (6).

∅g

vol.% vol.%

ρF

wt.% vol.%

+ ∅g

∅g

wt.% wt.%

·ρL

wt.% vol.%

− ∅g

wt.% wt.%

·ρF

wt.% vol.%

(6)

where ρF is the CMF/CNF density [37] assumed as 1500 kg/m3 , and ρL the density of the suspension. If the CMF/CNF dose is very low, under 1 wt.%, the density of the suspension could be approximated to the water density.

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In this paper, different CMF/CNF hydrogels with various fibrillation degrees have been characterized and dispersed at different stirring speed levels. The behavior of the obtained samples was analysed based on the Øg data. TEM images and AR theories have been used to validate the effectiveness of the Øg parameter to characterize the dispersions. Based on this method, the optimal stirring-speed conditions of CNFs have been applied for an industrial application. Therefore, the effect of the dispersion degree of CNF hydrogels, before the mixture of nanocellulose with the pulp on the reinforcement of recycled old corrugated cardboard (OCC) sheets has been evaluated by measuring mechanical (bursting index, short-span compressive test index, tensile index, tear index) and physical properties (bulk and porosity) of the handsheets. In addition, the effect of disintegrating CNF and OCC together in a pulper, without a previous dispersion of CNF, was also studied. 2. Materials and Methods 2.1. Materials CMFs/CNFs form a three-dimensional network structure within the hydrogel that is modified when the suspensions are prepared at different dispersion degrees. Four types of CMFs or CNFs have been used in this study from three different sources. The analysis of samples with different fibrillation degrees is crucial to validate the hypothesis of the study. The first sample was a microcellulose obtained from grinded cotton linters (C-CMF) with high purity cellulose (Sigma-Aldrich, St Louis, MO, USA). C-CMF were prepared without any pretreatment and mechanically fibrillated in a laboratory homogenizer PANDA PLUS 2000 manufactured by GEA Niro Soavy (Parma, Italy) using six progressive passes of homogenization from 300 to 900 bars. Commercial recycled newspaper with an ash content of 14% was used to prepare two types of products with different fibrillation, CMF (R-CMF) and CNF (R-CNF). Both were disintegrated at 30,000 revolutions and 3.0 wt.% consistency in a pulp disintegrator (PTI, Vorchdorf, Austria). To obtain R-CMF, the cellulose pulp was refined at 5000 revolutions in a PFI mill (Hamjern Maskin AS, Hamar, Norway) and six steps of homogenization at 600 bars were applied. R-CNF was obtained by a chemical pre-treatment with 2,2,6,6-tetramethylpiperidin-1-oxyl-radical (TEMPO) according to Saito et al. [42] using 1 mmol NaBr and 10 mmol NaClO/g of pulp. Once the pulp was oxidized, a filtration cleaning process was performed using distilled water and four steps of homogenization at 600 bars have been applied. The third raw material was obtained from Eucalyptus globulus ECF bleached kraft pulp, kindly supplied by Torraspapel, S.A. (Zaragoza, Spain), with 74% of cellulose and 18% of hemicellulose as its main components. The CNF (E-CNF) were obtained by TEMPOmediated oxidation with 2.5 mmol of NaClO/g of dry pulp. Then, six steps of homogenization at 600 bars were applied. All hydrogels were stored at 4 ◦ C at ~1 wt.% to avoid their aggregation, after adding some drops of glutaraldehyde as bactericide (5 drops/L) to avoid bacterial growth, until they were used. The raw materials and the pretreatments used to obtain the CMFs/CNFs were selected to obtain a large variation of the properties. Dry CMFs/CNFs composition was characterized before the HPH treatment. Cellulose, hemicellulose, lignin (soluble and insoluble), extractives, and ashes were measured. Firstly, extractives of the samples were determined via Soxhlet extraction and ash content was determined via calcination according to TAPPI T204 and T211, respectively. Cellulose, hemicellulose and lignin content were obtained following NREL/TP-510-42618. 300 mg of sample was hydrolyzed for 1 h with 3 mL of 72 wt.% H2 SO4 . Then, 84 g of water was added in the sample and then introduced in the autoclave for one hour at 121 ◦ C. The hydrolyzed samples were vacuum filtered, the insoluble lignin remained in the filter and the soluble part was obtained in the UV-visible spectrophotometer by measuring the absorbance of the filtrate. Hemicellulose and cellulose content were analyzed using high performance liquid chromatography (HPLC) from the filtrate after neutralization with CaCO3 and filtered. This process was not carried out in

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C-CMF due to the sample was not pretreated and directly was homogenized. CNFs/CMFs from recycled paper present a higher amount of ashes from the fillers added in the previous paper manufacture. On the other hand, the amount of cellulose is slightly reduced in the chemical pretreatment of R-CNF at the same time the insoluble lignin is also reduced. This is produced by the removal of lignin and amorphous cellulose during TEMPO-mediated oxidation. In the same way, the amount of cellulose also is slightly reduced in E-CNF respect to the initial cellulose value. However, this effect occurs to a lesser extent due to the lower amount of NaClO used in E-CNF pretreatment. CMFs/CNFs were characterized according to Balea et al. 2019 [10] and listed in Table 1. As for the chemical parameters, the number of carboxyl groups differs greatly between the CNFs and the CMFs, the latter with almost zero content since these samples have not been oxidized in the pretreatment. The superficial cationic demand obtained show also the same trend as carboxyl groups. The TEMPO-mediated oxidation influences on the fibrillation of the samples, with a higher transmittance of these samples that reach the range of nanofibrils. On the other hand, C-CMF from cellulose powder shows a low polymerization degree in a similar way than CNFs, however the diameter size is much larger than the other samples, with a low aspect ratio value. This effect is due to the ground of the sample that breaks the cellulose chains and decreases the aspect ratio without reaching the nanofibrillation of the sample. Diameter average of the other samples is in the nanoscale, although the R-CMF show a higher number of fibers in the microscale as nanofibrillation yield indicates. Table 1. Characterization of CMFs/CNFs. C-CMF

R-CMF

R-CNF

E-CNF

Dry composition Cellulose (%)

>99.9

56 ± 1

50 ± 1

72 ± 1

Hemicellulose (%)

13 ± 1

18 ± 1

Soluble lignin (%)

4.3 ± 0.5

10.0 ± 0.5

6.0 ± 0.5

Insoluble lignin (%)

12.5 ± 0.5

5.3 ± 0.5

Extractives (%)

1.8 ± 0.1

2.0 ± 0.2

0.3 ± 0.1

Ashes (%)

<0.1 *

12.5 ± 0.3

14.0 ± 0.5

3.0 ± 0.5

Chemical parameters Carboxyl Groups (mmol/g)

0.06

0.07

0.81

0.59

Superﬁcial cationic demand (meq/g)

0.06

0.04

0.62

0.80

Morphological parameters Transmittance 400 nm (%)

2.1

1.8

15.4

83.5

Transmittance 800 nm (%)

9.2

8.7

35.7

94.8

Polymerization Degree (monomeric units)

229

703

201

440

Nanoﬁbrillation Yield (%)

Diameter (average)

~5 μm

44 nm

19 nm

28 nm

* In accordance with the instructions of the manufacturer.

2.2. Methods 2.2.1. Determination of Gel Point in Suspensions The dispersion of nanofibrils was evaluated before its application, according to the methodology described by Martinez et al., based on the settling of samples to calculate Øg [35]. They analyzed the relation between the sediment concentration and the compressibility effects, redefining the Øg and developing Equation (1), which later was simplified in Equation (2). To prepare sedimentation experiments, suspensions with different CNF hydrogels were prepared using deionized water and 200 μL of crystal violet 0.1 wt.% to

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dye the ﬁbres [32]. Samples were agitated at several velocity gradients (G) up to 3000 s−1 using an overhead stirrer Heidolph RZR 2051 (Heidolph Instruments GmbH & Co. KG; Schwabach, Germany). Then, 250 mL of each suspension were settled into graduated cylinders until the sediment reached a steady value, which differs depending on the size of the ﬁbrils, and to obtain the complete deposition of the suspension. Figure 2 shows the graduated cylinders of R-CMF stirred at different agitations.

Figure 2. Graduated cylinders at different stirring speeds.

The Co was the same for all the samples to favor the comparison between the dispersion conditions. The Co was chosen to obtain a sediment height of approximately 4–12% of the total height, due to the difficulty to measure the height accurately at lower sedimentation values. On the other hand, higher sedimentation heights would cause the increment of concentrations that appears in Equation (2), for which the derivative has been substituted, moves away from the limit Hs/Ho to close to zero [39]. 2.2.2. Transmission Electron Microscopy To analyze the morphology of the fibers, a small sample of each CMF/CNF suspensions was collected after being stirred. They were analysed in the Centro Nacional de Microscopía (Madrid, Spain) by TEM with a JEM 1400 microscope (JEOL, Tokyo, Japan). To prepare TEM samples, CMF/CNF suspensions were diluted until 0.01 wt.%, and a drop was settled on a copper grid covered with a carbon coating and dried. Image J software was used to process the images. 2.2.3. Preparation and Characterization of Reinforced Cardboard Sheets E-CNF was used to validate the effect of CNF hydrogel dispersion on paper strength. Øg was used as a tool to determine the best conditions of papermaking application to enhance mechanical properties. Recycled OCC was used in the preparation of sheets due to the importance to increase the strength of cardboards for packaging [43]. OCC and CNF were disintegrated separately and then blended. OCC pulp was prepared through disintegration of 70 g of dry OCC in 2000 mL of tap water (3.5 wt.%) by using a pulp disintegrator according to ISO 5263-1 standard [44]. The OCC was left to soak 24 h before disintegration to favor fiber swelling. Separately, the E-CNF solutions (1 kg/m3 ) were prepared with CNF and tap water in the high-speed overhead stirrer for 10 min at several G values from 3 to 3000 s−1 . To prepare the handsheets, OCC-CNF pulp suspension (1.0 wt.%) were prepared from both products stirred separately and mixture with a ratio 95.5 wt.% OCC/4.5 wt.%

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CNF. Then, cationic starch (0.5 g CS/100 g dry pulp) was added as retention agent and stirred for 30 min at low speed previous the sheet formation. Finally, pulp suspensions were prepared with basis weight of 80 g/m2 according to standard ISO 5269-2 by using a Rapid Köthen sheet former [45] (PTI, Vorchdorf, Austria). Handsheets were conditioned at 25 ◦ C and 50% humidity for at least 24 h before physical and mechanical characterization. In addition, to compare the effect of OCC and CNF disintegrated by separate or together, OCC and CNF were stirred at the same time in the pulper at 3000 s−1 for 10 and 60 min (30,000 and 180,000 revolutions) with the same rate CNF/OCC as previously. To characterize the handsheets, mechanical properties were calculated using the average grammage of handsheets. Then, bursting strength index (kPa·m2 /g), SCT index (N·m/g), tensile strength index (kN·m/kg) and tear index (mN·m2 /g) were evaluated. Tensile strength was measured in an MTS Criterion Mode 43 from MTS Systems Corporation (Eden Prairie, MN, USA), following ISO 1924-3 standard [46]. Bursting strength was determined using a Messmer Büchel digital hydraulic board burst tester (Veenendaal, Netherlands) according to ISO 2759 standard [47]. A short span compression tester (Messmer Büchel, Veenendaal, Netherlands) was used to measure the short-span compressive test (SCT) according to TAPPI T826 standard [48]. Finally, tearing resistance was measured with a Tearing Tester from Lorentzen & Wettre (Stockholm, Sweden) according to ISO 1974 standard [49]. Physical properties measured were porosity, basis weight, and thickness. Porosity (μm/Pa·s) was evaluated in a Bendtsen Porosity Tester number 8699 from Andersson & Sørensen (Copenhague, Denmark) according to ISO 5636-3 [50]. Basis weight and thickness were determined according to ISO 536 and ISO 534, respectively [51,52]. Finally, bulk (cm3 /g) indicates the thickness in relation to the basis weight. 3. Results and Discussion 3.1. Evaluation of the Dispersion Degree of CMF/CNF Suspensions Øg results were obtained by sedimentation of the CMFs/CNFs until the formation of a stable deposit. In the case of R-CNF and E-CNF with smaller sized ﬁbers, the clear zone at the top of the cylinder is not formed at the low concentrations required for Øg . This fact is due to the small size of ﬁbers and a slow sedimentation, not allowing the distinction of the clear and coalescence layer at short times [32]. Therefore, the sedimentation curve obtained is quite different to the conventional one and only the interphase that indicates the formation of deposits is observed, in the base of the cylinders. At the beginning, the deposits increase over the time due to the compaction of part of material from the coalescence layer until all material has a compaction grade enough to be visible. In this point, we observe a clear separation of the compacted material that continues to compress until the sample has completely sedimented [32]. The height of this layer decreases until the height does not vary with time, and then, Øg is calculated. On the other hand, C-CMF and R-CMF show a conventional sedimentation. Figure 3 shows the Øg of the different CMF/CNF hydrogels at different stirring speeds. To facilitate the study of dispersion, Equation (3) was used to simplify the experimental labour using a unique Co , the same for all stirring speeds but different between hydrogels, having as long as possible a Hs /Ho from 4% to 12%. Co used were 1.5 kg/m3 for C-CMF, 0.15 kg/m3 for R-CMF, 0.25 kg/m3 for R-CNF and 1 kg/m3 for E-CNF. The use of the same Co to calculate the Øg does not allow its estimation with precision at the higher speed of C-CMF, R-CMF, and R-CNF, since the sediment height was very scarce. Therefore, these values were not shown in Figure 3 although they would be used in the estimation of AR in Figure 4. Increasing the velocity gradient, we can observe a decrease in the Øg decrease until a minimum value, then at a certain velocity gradient, Øg increase again. In those samples that presented a very low deposit at high speed (2500 s−1 for R-CMF and R-CNF and 500 s−1 for C-CMF) the Øg should be higher than the last value calculated in Figure 3 for each hydrogel.

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C-CMF R-CMF R-CNF E-CNF

25 5 1 2

200

2000

Velocity gradient, G (s-1)

Figure 3. Gel point vs. stirring speed.

150 125

Aspect Ratio

Gel point (kg/m3)

125

100 75 50 25 0 2

200

Velocity gradiant G,

2000

(s-1)

C-CMF (CN)

R-CMF (CN)

R-CNF (CN)

E-CNF (CN)

C-CMF (EMT)

R-CMF (EMT)

R-CNF (EMT)

E-CNF (EMT)

Figure 4. Aspect ratio of the four hydrogels at different stirring speed according to Crowding Number (CN) and Effective Medium Theory (EMT) theories.

To explain the possible modiﬁcations on the CMF/CNF suspensions with the agitation, the AR is calculated by the Equations (3)–(6) to obtain the relationship between both parameters, using the two theories, CN and EMT, and setting the AR as the independent variable according to Equations (7) and (8). Figure 4 shows AR values of the four hydrogels at the different stirring speed conditions using both theories. In this ﬁgure, the AR of C-CMF, R-CMF, and R-CNF stirred at high stirring speed was possible to be graphed although with a large accuracy error, so its representation is drawn in black. ⎛ AR(EMT) = 3.61·⎝ ⎛ AR(CN) = 5.98·⎝

∅g

kg m3

1000

∅g

kg m3

1000

⎞−0.567 ⎠

(7)

⎞−0.5 ⎠

(8)

In all hydrogels studied, AR has a similar trend with a maximum at intermediate stirring speeds. At low agitations, water and hydrogel are hardly mixed, but the crossed

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networks of fibrils start to separate due to the shear forces at higher stirring speeds. In addition, in E-CNF hydrogel in which gelation has occurred after homogenization, clusters begin to break. Then, it is observed that increasing stirring speed, an increase in Hs /Ho is produced that indicates the E-CNF structure is more open and spongier with the dissolution of clusters. The fact that relative height was in the denominator of Equation (2) makes that Øg decrease during this first period until a certain velocity gradient value, in which the Hs /Ho is maximum. Then, at higher speeds, Hs /Ho decreased because the hydrogen bonds between fibrils would break them and, therefore, the networks would be destroyed. In addition, the mechanical forces during agitation would shorten the length of the fibrils that are individual separated, compacting them in the base of the graduated cylinders and, as a consequence, increasing Øg . However, the optimal stirring speed to obtain as many dispersed fibers as possible without breaking the network is different for each hydrogel. Analyzing them one by one, C-CMF show the highest Øg studied (Figure 3), due to cotton that was ground in powder obtaining the lowest aspect ratio during all agitation stages, as Figure 4 shows. The high crystallinity of the sample with a high rigidity makes the sample not produce a network of fibers without an increase in the sponginess with the stirring. The AR in C-CMF is almost invariable with a maximum obtained at very low agitation conditions, with a velocity gradient around 10 s−1 associated to the initial agglomeration of the sample. This hydrogel without any pretreatment contains mainly microfibrils with scarce branches from the primary structure due to the powder state of the sample, so the crossover network is hardly possible and at low agitation the effect of fiber breakages is already evident. However, moderate agitation produces a strong shortening of the fibers as aspect ratio shows. On the contrary, the R-CMF shows a higher number of branches around the cellulose backbone due to the pulp was refined as pretreatment before the homogenization, this mechanical treatment produce an increase in the AR compared with other pretreatments as TEMPOmediated oxidation or enzymatic hydrolysis [53]. A greater crosslinking of networks as in R-CMF would produce, at low agitation speeds, the increase in the sponginess stretching the networks as it shakes. A higher velocity gradient is required to obtain the spongier network, above 500 s−1 . Then, the high hydrodynamic conditions would produce the breakage of refined microfibrils separating them from the main structure and at the same time the shortening of fibrils. As for CNF hydrogels, R-CNF obtained from the same raw material than R-CMF but pretreated with TEMPO-mediated oxidation instead of refining, shows a minimum Øg around 50–100 s−1 , less agitation than R-CMF. This is because TEMPO-mediated oxidation produces electrostatic repulsion between microfibrils and the breakages of cellulose chains, favoring the fibers separation with the breakage of primary structures. Both effects would reduce the crossover between networks and, therefore, at lower stirring speeds the breakage of the fibers is observable. Finally, the other CNF hydrogel, E-CNF with an almost total nanofibrillation, shows the minimum Øg around 500 s−1 . Despite the higher nanofibrillation yield of E-CNF, the number of carboxyl groups is less than R-CNF due to a lower NaClO content in the TEMPO-mediated oxidation, decreasing the repulsion of fibrils. This fact would produce less breakage and separation of fibers and, therefore, E-CNF keep a greater crosslinking of the fibers that are more difficult to separate mechanically requiring more energy. In addition, in E-CNF is not produced a great variation of deposits at very high stirring speeds, probably due to the almost total nanofibrillation of the fibers that prevents a great variation of heights from occurring. 3.2. Validation of Gel Point Methodology to Quantify Nanocellulose Dispersion To verify the shortening of the fibrils and the AR, the two hydrogels from the same raw material were selected in order to see the effect of refining and TEMPO pretreatments on the dispersion degree. TEM images of R-CNF and R-CMF were taken at different stirring speeds and magnifications from 400× to 10,000×. Diameter distributions in logarithmic

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scale are presented in Figure 5 together with a TEM micrograph of each hydrogel at different agitation conditions.

Figure 5. CMF/CNF diameter distribution and TEM images at different stirring speeds: (a) R-CNF diameter distribution; (a1) 3 s−1 ; (a2) 70 s−1 ; (a3) 125 s−1 ; (a4) 500 s−1 ; (a5) 2500 s−1 ; (b) R-CMF diameter distribution; (b1) 50 s−1 ; (b2) 500 s−1 ; (b3) 900 s−1 ; (b4) 2500 s−1 .

The differences between both hydrogels are related to the pretreatments used to obtain the hydrogels, which produce the variation of ﬁber size. R-CNF has a higher number of

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fibers in the nanometric scale due to the more intensity of chemical pretreatment than R-CMF. When the velocity gradient is low, R-CNF and R-CMF are not well dispersed in the solvent, as part of the fibrils are positioned together, and if they do not separate with more agitation, they settle as a single particle, forming aggregates or clusters. On the other hand, when the agitation is higher than that performed in the minimum Øg , the fibrils network is destroyed due to the mechanical forces and the fibrils are compacted in the base of the graduated cylinders as the representation of fibre network disposition shows in Figure 6. Moreover, Table 2 shows statistical parameters of the diameter fibers including the number of samples analyzed in TEM images, the geometric mean with a 95% confidence interval, the median of each sample (to avoid the deviation of the statically tails) and the 95th percentile to evaluate the diameter of the higher fibers discarding values that may be exceptional. Finally, the length of fibrils was calculated from the AR values and the geometric mean diameter.

3s-1

70s-1 125s-1 500s-1 2500s-1 R-CNF

50s-1 500s-1 900s-1 2500s-1

R-CMF R

Figure 6. Representations of ﬁbril network in the deposit of the graduated cylinders at increasing agitation speeds. Table 2. Statistical parameters of diameter distribution of CMF/CNF samples from TEM images and estimation of aspect ratio and length of ﬁbers. Velocity Gradient (s−1 )

Geometric Mean of Diameter (nm) 95% Conﬁdence Interval

Mean

Diameter Median (nm)

Length (μm)

Diameter D(0.95) (nm)

Number of Samples Measured (Fibers)

EMT

261

1.89

1.67

R-CNF 3

(17.4, 20.3)

18.8

18.9

50.7

(14.4, 16.5)

15.4

15.3

38.0

237

1.72

1.53

125

(14.0, 15.9)

14.9

14.1

39.0

311

1.64

1.46

500

(11.8, 13.6)

12.6

11.8

40.7

366

1.17

1.02

2500

(9.9, 11.5)

10.7

10.9

27.4

242

<0.9 *

<0.8 *

R-CMF 50

(39.0, 49.5)

43.9

40.0

379

316

5.44

4.93

500

(29.5, 36.4)

32.8

31.5

145

259

4.77

4.41

900

(29.7, 35.3)

32.4

33.9

136

366

4.34

3.98

2500

(27.4, 32.4)

29.8

26.8

111

295

<3.2 *

<2.9 *

* Gel point at 2500 s−1 was not determined with precision due to the low deposits obtained. Therefore, a minimum value to obtain the maximum length of ﬁbrils at that stirring speed is assumed.

Analyzing both samples separately, R-CNF, with a high homogeneity of the ﬁbrils due to TEMPO pretreatment, show at low velocity gradient (~3 s−1 ) the initial gel state of the

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hydrogel. At this low agitation speed, R-CNF is not well dispersed with clusters in the suspension. The nanofibrils are not effectively separated and the surface area low with the highest diameter geometric mean. Increasing velocity gradient up to 70 and 125 s−1 , the lowest Øg are obtained and the length of fibers barely changes but the number of nanofibers with high diameter (>30 nm) decreases, indicating that clusters disappeared and the network is slightly spongier. Since the length of the fibers is maintained and the mean diameter decreases, the highest AR is obtained. Higher gradients as 500 s−1 produce an increase in Øg associated with the shortening of fibers and, to a lesser extent, a reduction in diameter. Extreme agitation (around 2500 s−1 ) almost halves the length of the fibers and sedimentation deposits are very compact, with the reduction of the percentile 95th below 30 nm. R-CMF shows the same trend as R-CNF but at different stirring speeds. Low agitation (50 s−1 ) shows the higher length as the same time the higher diameter due to clusters and fibers not separated. Then, with the intermediate agitation (500 s−1 ), the minimum Øg , fiber length is almost maintained but shows a drastic decrease in the diameter distribution due to the separation of the biggest fibers producing a spongy network. The effect of refining produces the separation of the microfibrils but not their breakage, resisting a higher speed than R-CNF pretreated by TEMPO mediated oxidation in which there are less bundles of fibers around the primary structures that allow the creation of networks. However, as in R-CNF, higher velocity gradients than the minimum Øg (around 900 s−1 ) show the break of the open network with the shortening of the length of nanofibrils while the diameter is maintained. This effect is also observed with an extreme agitation that halves the fiber length. In short, the agitation (stirring speed) at which the minimum Øg is produced for each CMF/CNF hydrogel would be the best agitation conditions to avoid aggregation of CMF/CNF on the one hand, and the shortening of the fibrils on the other. 3.3. Effect of CNF Dispersion on the Mechanical and Physical Properties of Paper The effect of CNF dispersion degree before being added to the OCC pulp disintegrated has been studied on the reinforcement of cardboard. In addition, the effect of the dispersion of CNF and the disintegration of OCC pulp at the same time has also been studied. E-CNF dispersed at different levels, the same used to determine the minimum Øg (Figure 3), has been studied before the addition in the OCC pulp that was previously disintegrated at 30,000 revolutions (around 3000 s−1 ) in a pulp disintegrator. Figure 7 shows physical (porosity and bulk) and mechanical properties (tensile, bursting, SCT and tear indexes) of the handsheets prepared when CNF was stirred separately. In addition, Øg and AR were included in Figure 7a,c, respectively, to favor the comparison of the samples. On the other hand, Figure 8 shows the results obtained when the dispersion of CNF and disintegration of OCC was carried out at the same time. OCC blank has the highest Bendtsen porosity of 10.1 μm/Pa·s. Substituting 4.5 wt.% OCC by CNFs previously stirred and added after OCC pulping, porosity is reduced in more than 60% in all cases. This value depends on the agitation speed of CNFs, with a lower reduction at 3 s−1 , due to CNFs not being well dispersed yet. However, at 100 s−1 it is produced the higher reduction of the porosity up to 1.4 μm/Pa·s that represents a reduction of more than 86%. This fact suggests a higher occupation of pores when CNFs are applied and well dispersed in the handsheets [54,55]. This porosity is almost maintained with a slightly increase until 500 s−1 . Then, porosity increases again at 3000 s−1 until 2.5 μm/Pa·s. This fact is produced at the same time Øg increases again, due to the shortening of the nanofibers and the break of the network leading to a decrease in the occupation of pores. In addition, a decrease in the CNF size could produce a higher loss of CNFs during the production of the handsheets in the sheet former, moving a higher CNF propertion to the process water. As for the other physical property tested, the bulk, all samples studied have the same result as Figure 7b shows, indicating the replace of a low content of OCC by CNFs do not have influence on the thickness neither the basis weight of the handsheets.

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0 Blank

100

300

500

b) Bulk (cm3/g)

Øg (kg/m3)

Porosity (μm/Pa·s)

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0 Blank

3000

Tensile Index (kN·m/kg)

30 36

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Figure 7. Mechanical and physical properties of handsheets prepared with OCC disintegrated for 10 min (3000 s−1 ) and CMF dispersed at different speeds for 10 min: (a) Porosity and Gel Point; (b) Bulk; (c) Tensile Index and Aspect Ratio; (d) Bursting Index; (e) SCT Index; (f) Tear Index.

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Figure 8. Mechanical properties of handsheets prepared with CNF and OCC stirred together at different speeds: (a) Porosity; (b) Bulk; (c) Tensile Strength Index; (d) Bursting Index; (e) SCT Index; (f) Tear Index.

Moving to mechanical properties, tensile strength is studied in Figure 7c. OCC blank has a tensile index of 33.1 kN·m/kg. When CNFs are stirred at several speeds, the tensile index increases progressively with the stirring speed until 40.7 kN·m/kg, when CNFs are stirred at a velocity gradient of 500 s−1 , in which the Øg is minimal with the highest AR. It is produced an increase of 23% respect to blank and 18% compared with the sample with CNFs stirred at the low speed. This fact is due to the progressively separation of the CNF clusters from the gel with the agitation, with a more opening CNF network and better homogeneity in the suspensions and then a better distribution of the fibers in the final matrix, increasing the strength. However, an excess on the velocity gradient, above the minimum Øg (3000 s−1 ), does not improve the results with a tensile index of 37.7 kN·m/kg and an increase of 13.7% respect to blank. This fact may be due to the break of the fibers in

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pieces, reducing their impact to cover the pores of the fibers and the ability to interlace the fibers of the matrix reducing the tensile strength. As other researchers have demonstrated, the bursting index (Figure 7d) shows the same trend as the tensile index [56]. OCC blank has a bursting index of 1.87 kPa·m2 /g. Handsheets with CNFs increase progressively until a gradient velocity of 500 s−1 , with an increase of 25% in the bursting strength (2.34 kPa·m2 /g). However, a higher speed makes an increase in burst strength of only 17%. The same occurs with compression strength, measured with the SCT index in Figure 7e. The higher SCT is obtained when the CNFs are stirred at 500 s−1 , with an increase of 21% respect to the blank, then the SCT Index is reduced more than the obtained with 100 s−1 . Finally, the tear index is evaluated in Figure 7f with a blank value of 8.74 mN·m2 /g. The addition of CNFs stirred at 3 s−1 decreases the tear index in 8.2%. This reduction is also observed in other studies, when CNFs are applied in bulk to prepared handsheets due to the reduction of the length of the fibers in the matrix making the tearing easier [10,57]. Low stirring speeds do not improve the results of blank until CNFs are stirred at 500 s−1 , maintaining tear index of blank with a slightly increase of 1.1%. This effect could be due to a good disposition of the CNFs in the OCC matrix, avoiding their aggregation and the tearing weakness. Extreme agitation of CNFs, 3000 s−1 , produces only a little decrease in the tear index but also maintained the blank value. In summary, looking at all properties together, the optimal conditions to improve mechanical properties of recycled cardboard were CNFs stirred at 500 s−1 rpm with the best results in all mechanical properties studied and maintaining bulk and the tear of the OCC matrix without CNFs. These conditions coincide with the minimum Øg of E-CNF (around 500 s−1 ). Besides the importance of dispersing CNFs adequately to prepare the handsheets, OCC disintegration is also a key factor to analyze. For that, the influence of OCC disintegration and CNF dispersion in the same pulper or separately at different stirring speeds has been studied. Figure 8 shows physical and mechanical properties of handsheets prepared with OCC and CNFs disintegrated and dispersed, respectively, at the same time in the same pulper at 3000 s−1 for 10 min and 60 min. Blank prepared only with OCC and stirred 10 min is the same as in Figure 7, being able to compare the results of stirred OCC and CNF together or separately. Bendtsen porosity of Figure 8a shows the variation of adding CNF in the pulp matrix in both speeds. A higher stirring speed does not produce a high diminution of porosity, being ineffective a higher time of disintegration. In addition, both samples are more porous than when OCC and CNFs are stirred separately. This fact could be due to in agitation separately the CNFs are placed more superficial whereas in the stirring together both materials mix with each other in a higher extent. In respect to bulk, as in Figure 7, there are not differences in respect to blanks without CNFs. As for the mechanical properties, tensile, bursting, and SCT indexes show the same trend (Figure 8c–e). In the three indexes, there is a decrease in these properties when the blank is stirred for 60 min due to a higher break of the fibers in the disintegrator. As for the sheets with OCC and CNF in both times of stirring, they have an increase in the properties respect to the blanks, even more after 60 min of agitation. Among the results stand out the tensile index of OCC and CNF stirred together for 60 min with 44.6 kN·m/kg. This property has the highest difference with the tensile of OCC (10 min) and CNF (500 s−1 ) stirred separately with 40.7 kN·m/kg (Figure 7c), although if we compare with the OCC and CNF stirred together but only 10 min (39.1 kN·m/kg) we see that the OCC disintegration and CNFs dispersion separately is still better. As for the bursting and SCT indexes, the separated stirring of OCC and CNFs (500 s−1 ) shows better properties than the obtained together independently the time selected (Figure 8d,e). This fact indicates that, as in porosity, the mix of CNF with OCC after its disintegration favors the mechanical properties of the sheets, due to a more external situation of CNF whereas a more blended situation reduces the efficiency of CNF that is more mixed in the bulking agent. Finally, the tear index in Figure 8f indicates that this property barely has influence in the handsheets when

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they are prepared with OCC and CNFs at the same time respect to the blanks, obtaining the same maintenance of the properties as stirring OCC and CNFs separated at the optimal speed. Therefore, to sum up among the samples with OCC stirred for 10 min, the agitation separately of OCC and CNFs, these dispersed in the optimal conditions in which the minimum Øg is obtained (500 s−1 ), producing the best results in tensile, bursting, and SCT indexes, maintaining the tear index, and reducing notably the porosity. Comparing these results with those obtained after 60 min of stirring the OCC and CNFs together, the only property that increases is the tensile index, such that a longer disintegration time would be discarded due to the higher energy consumption. 4. Conclusions Dispersion of CMF/CNF hydrogels has been quantified for the first time based on the Øg methodology and validated by the morphological characterization with TEM. The important effect of this key parameter has been developed to facilitate the optimal use of CMFs/CNFs in applications at industrial scale. The stirring speed required to obtain the maximum expanded CMF/CNF network without clusters and without breaking down of the network depends on the fibrillation degree and the charge of each CMF/CNF hydrogel. Increasing stirring speed produces a decrease in the Øg that indicates the CMF/CNF structure is more open and spongier. However, too high levels of agitation produce an increase in the Øg because the nanofibrils are broken and separate from the network by the high mechanical forces from the stirring of the suspensions; the CMF/CNF network collapses, which results in the compaction of the nanofibrils. Based on the results, it is concluded that the optimum stirring speed for a given CMF/CNF sample is the one corresponding to the minimum Øg , which in turn corresponds to the maximum AR. At the minimum Øg , the aggregation of nanofibrils is avoided as well as the reduction of their surface area, observed when CMF/CNF hydrogels are not well dispersed, and the shortening of the fibers is minimized. This value can be easily obtained on-site and will allow for the optimization of industrial CMF/CNF applications. However, the optimal dispersion of each CMFs/CNFs must be studied separately, due to depending on several parameters such as the fibrillation, treatments in the production, or composition. This technique has been tested in a real application, as in the case of the reinforcement of the mechanical properties of cardboards. When E-CNF suspensions are dispersed at different stirring speeds and then added to the OCC matrix disintegrated separately, the best mechanical properties were obtained when CNFs were dispersed at the minimum Øg . At this dispersion degree, there is not an excess break of the fibers nor the presence of clusters or agglomerations that allow the ability to interlace the fibers of the matrix with the CNFs. In addition, this configuration also presents better properties than when the OCC was disintegrated at the same time that the CNFs were dispersed. The separate agitation of OCC and CNFs allows CNFs to be placed more superficially, covering the pores in the OCC network, without an excessive mixture of both components avoiding the CNFs being located more internally, reducing the effect of covering pores and taking part of the own matrix. Author Contributions: Conceptualization, A.B. (Angeles Blanco) and C.N.; formal analysis, J.L.S.-S. and M.C.M.; funding acquisition and project administration, C.N.; investigation, J.L.S.-S. and A.B. (Ana Balea); supervision, M.C.M. and A.B. (Angeles Blanco); writing of the original draft, J.L.S.-S.; writing of review and editing, A.B. (Ana Balea), M.C.M., C.N., and A.B. (Angeles Blanco). All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Science and Innovation Ministry of Spain (PID 2020113850RB-C21) and the support of Universidad Complutense de Madrid and Banco de Santander for the grant of J.L. Sanchez-Salvador (CT17/17). Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable.

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Data Availability Statement: Not applicable. Acknowledgments: The authors wish to thank the Science and Innovation Ministry of Spain for the support of the project with reference PID 2020-113850RB-C21 as well as the support of Universidad Complutense de Madrid and Banco de Santander for the grant of J.L. Sanchez-Salvador (CT17/17). Besides, the authors express their gratitude to the Centro de Investigación Forestal of INIA (Madrid) for having allowed them to use its facilities, as well as to the Spanish National Centre of Electronic Microscopy for the support during image acquisition. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semiburned rice straw ash as modified papermaking fillers 1 2 3 FATMA A. MORSY , SAID M. EL-SHEIKH , AHMED BARHOUM .

Silica (SiO2) nanoparticles and silica/calcium carbonate (SiO 2/CaCO3) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO2 nanoparticles and SiO2/CaCO3 nanocomposites was carried out using Na 2SiO3 solution that was prepared from SBRSA and CaCO3 nanoparticles of 30–70 nm. The targeted SiO2/CaCO3 nanocomposites were prepared with different molar ratio of SiO2:CaCO3 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800°C for 2h. The prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO2 nanoparticle and semi-crystalline shell of SiO2 coated CaCO3 core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper. Application of the prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO3 (PCC) filler. The results showed that the retention of SiO 2 nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO 2:CaCO3 molar ratio. Contact information: 1 Paper and Printing Lab., Chemistry Department, Faculty of Science, Helwan University, Cairo, Egypt 2 Nanostructure Materials Division, Advanced Materials Department, Central Metallurgical Research & Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Cairo, Egypt 3 Department of Materials and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium King Saud University, Arabian Journal of Chemistry, http://dx.doi.org/10.1016/j.arabjc.2014.11.032 Creative Commons Attribution 3.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 12

Article 4 – Nano-fillers from Straw Ash

Arabian Journal of Chemistry (2019) 12, 1186–1196

King Saud University

Arabian Journal of Chemistry www.ksu.edu.sa www.sciencedirect.com

ORIGINAL ARTICLE

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash as modiﬁed papermaking ﬁllers Fatma A. Morsy

a,*

, Said M. El-Sheikh b, Ahmed Barhoum

Paper and Printing Lab., Chemistry Department, Faculty of Science, Helwan University, Cairo, Egypt Nanostructure Materials Division, Advanced Materials Department, Central Metallurgical Research & Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Cairo, Egypt c Department of Materials and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium b

Received 21 June 2014; accepted 17 November 2014 Available online 24 November 2014

KEYWORDS Nano silica; Core–shell SiO2/CaCO3; Semi-burned rice straw ash; Fillers; Paper properties

Abstract Silica (SiO2) nanoparticles and silica/calcium carbonate (SiO2/CaCO3) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO2 nanoparticles and SiO2/CaCO3 nanocomposites was carried out using Na2SiO3 solution that was prepared from SBRSA and CaCO3 nanoparticles of 30–70 nm. The targeted SiO2/CaCO3 nanocomposites were prepared with different molar ratio of SiO2:CaCO3 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800 C for 2 h. The prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO2 nanoparticle and semi-crystalline shell of SiO2 coated CaCO3 core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper. Application of the prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO3 (PCC) filler. The results showed that the retention of SiO2 nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO2:CaCO3 molar ratio. ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

* Corresponding author. Tel.: +20 01019830883; fax: +20 2 25552468. E-mail address: fatma_a_morsy@yahoo.com (F.A. Morsy). Peer review under responsibility of King Saud University.

Production and hosting by Elsevier

1. Introduction In paper industry, finely-divided white mineral fillers are added to increase the paper brightness, opacity and improve the paper’s quality while having reduced costs by replacing the fibre (Gupta, 2007).The filler particles serve to fill the spaces

http://dx.doi.org/10.1016/j.arabjc.2014.11.032 1878-5352 ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash and crevices between the fibres; thus improving the properties of the sheet. The common papermaking fillers are clay (kaolin), calcium carbonate, talc (magnesium silicate) and titanium oxide (Smook, 1997). Modification of calcium carbonate filler with silica-containing substances has been proposed to obtain modified filler suspension with high degree of stability and acid-resistant properties (Snowden et al., 2000; Kim and Lee, 2002; Shen et al., 2008, 2010). Various surface coating approaches have been introduced to improve the light scattering of pigments. The light scattering from calcium carbonate particles can be increased by coating the granules with a thin continuous layer of higher refractive index material (Lattaud et al., 2006). Silica has good properties such as a high specific surface area, high gas absorbability and high oil absorption. These properties are added to the coated pigment specifications (Park et al., 2007). It is also one of the most effective chemicals for paper coating due to its high brightness, opacity, porosity, hydrophilicity. The application of these materials, for instance, as fillers in the paper industry may contribute to the fibre-tofibre bonding, when coated with silica thus improving paper strength (Gamelas et al., 2011; Lourenço et al., 2013). Silica is introduced as nano-particles with core–shell structure representing a new type of constructional units; such materials enhance physical and chemical properties, thus allowing a broader range of applications compared to the single components (Hall et al., 2000; Vestal and Zhang, 2002; Bala et al., 2007). The objective of this work is to prepare fillers in a nano- size from waste material to reduce disposal and pollution problems in addition to improving paper filler performance. Also to avoid the reverse effect of filler in reducing the paper strength. The main goal is to prepare (a) nano-silica from the semiburned rice straw ash (b) silica/calcium carbonate nanocomposite. The prepared fillers were characterized, and therefore the effect on handsheet properties was investigated.

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icate Na2SiO3 solution was obtained from SRBRA by using alkali leaching process. All the leaching experiments were carried out in covered Teflon beaker (250 ml). Each experiment was performed by dissolving a calculated amount of NaOH in distilled water and then 10 gm of SBRSA was added gradually to attain stoichiometry (NaOH:SiO2) 3:1 and liquid/solid ratio 10/1. The mixture was heated at 100 C for 4 h under vigorous constant stirring. After the reaction time completed, the slurry was filtered then washed with distilled water. The concentration of the silica in the obtained solution was measured by ICP and the result showed that the dissolved silica equals 0.735 M with 94.5% extraction efficiency. Silica nanoparticles were obtained by adding gradually 12 wt.% H2SO4 solution to the prepared Na2SiO3 solution with constant stirring until a pH 10 is reached. The formed silica gel was aged for 24 h and then it was disintegrated, washed with water and ethanol then dried at 120 C in a drying oven for at least 24 h to produce silica xerogel. The dried xerogel was washed with distilled water to make sure it is free of Na2SO4 and calcinated at 300 C to produce SiO2 nano-particles (Zaky et al., 2008). 2.2.2. Preparation of nano-calcium carbonate

2. Experimental

CaCO3 nano-particles were prepared by using the reaction system Ca(OH)2–H2O–CO2 as described in our previous work (El-Sheikh et al., 2013; Barhoum et al., 2014). Bulk CaO was firstly calcined at 1000 C for 2 h then slaked into lime milk in mono-distilled water at 80 C. The lime milk was cooled to room temperature (20 C). At this temperature, the CO2 gas was injected into the lime milk (1000 mL min 1 flow rate and 1 M CaO concentration) with vigorous stirring. The pH value and electric conductivity of the reaction solution were recorded on-line with a pH-meter (Jenway 3305) and a conductometer (Jenway 4510). When the pH value decreased from 14 to 9 and the electric conductivity showed a sharp decrease, this was an indication that the reaction was completed, the CO2 flow was stopped. CaCO3 particles were obtained and dried at 120 C in a drying oven for at least 24 h.

2.1. Materials

2.2.3. Preparation of silica/calcium carbonate nanocomposite

A semi-burned rice straw ash (SBRSA) was obtained from gas production unit of rice straw located at El-Azazy village, Zagazig, Egypt. An analytical grade calcium oxide (CaO, 97% on a dry basis, Acros Organics) and pure CO2 gas (99.8% supplied by Industrial Gases Company, El-Hawamdia, Giza, Egypt) were used in the preparation of CaCO3 nano-particles. Bleached kraft hardwood and softwood pulps, polyacrylamide suspension (47% solid content) as a retention aid, commercial PCC (1.5 lm length and 250–300 nm in diameter) as reference ﬁller for comparison (supplied by Rakta Company, Alexandria, Egypt) were used for paper handsheet preparation. 2.2. Filler preparation 2.2.1. Preparation of sodium silicate and silica nano-particles A SBRSA sample was burned at 800 C for 2 h to remove all the residual hydrocarbons. The produced powder was then sieved. Fraction size less than 0.71 mm (about 54.77%) was selected to perform the experiments. Concentrated sodium sil-

SiO2/CaCO3 nanocomposites were prepared via a step-by-step method to produce a core–shell structure (Bala et al., 2007). The core CaCO3 nano-particles were obtained in the ﬁrst step of a carbonation method and SiO2 layer was coated on the core in the second step of sol-precipitation method from precursor of Na2SiO3Æ9H2O (Gamelas et al., 2011). The prepared CaCO3 nano-particles were dispersed in 150 mL distilled water using high shear mixer of 3000 rpm for 30 min. The prepared slurry was exposed to high ultrasound waves using the W385 Sonicator for 30 min. to completely break the agglomerates. The prepared Na2SiO3 solution was gradually added to the suspension. The molar ratio of SiO2/CaCO3 nanocomposites was designed and controlled to be 1:15, 1:10 and 1:5 of the samples CS1, CS2 and CS3, respectively. The mixture was heated up to 80 C with vigorous constant stirring. The pH value was adjusted to 9 by gradual addition of 6 wt.% H2SO4 solution for one hour. Then the mixture was aged for 3 h. The produced slurry was cooled, ﬁltered and rinsed with distilled water to be sure it is free of Na2SO4. The SiO2/CaCO3 nanocomposite powder dried at 120 C for 24 h then at 300 C for 3 h.

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2.3. Handsheet preparation

2.5. Characterization of the prepared handsheets

Handsheets of paper were prepared with target basis weight of 60 g/m2 according to TAPPI Standard T-205. The fibre employed in this study was a mixed chemical wood pulp with a hardwood/softwood ratio of 85:15 (wt.%). The prepared fillers (silica nano-particles and SiO2/CaCO3 nanocomposites) were added to the prepared pulp stock at 15% on dry pulp. Unloaded and commercial PCC loaded handsheets (reference handsheets) were also prepared for comparison. In advance, cationic polyacrylamide was added with a concentration of about 0.1% to dry pulp basis to increase the fillers’ retention.

The properties of paper handsheets were evaluated using standard testing for physical, mechanical and optical properties. The ash content was conducted in a mufﬂe furnace at 525 C

2.4. Characterization of the prepared nano-fillers The produced nano-fillers were characterized by different techniques as follows: X-ray diffractometer (XRD, Bruker AXS D8, Germany), with Cu Ka (k = 1.5406 Å) radiation and a secondary monochromator, was used to preform the phase identification of the prepared silica, CaCO3 nano-particles and SiO2/CaCO3 nanocomposites. X-ray fluorescence (XRF) Axios, Sequential WD-XRF, PANalytical 2005 (Netherlands) was used to determine the metallic ion impurities in SBRSA and the produced silica. Scanning Electron Microscope (SEM, JEOL instrument model JSM-5410) was used to characterize the microstructure of the obtained fillers. Transmission electron microscopy (TEM, JEOL-JEM-1230, Tokyo, Japan) was used to investigate the morphology information of the samples such as particle size and particle shape. Fourier Transform Infrared (FT-IR) spectra (Jasco FT-IR-3600 plus Japan) was used to detect the existence of organic compounds and lattice water incorporating of excess hydroxide species in the sample. Zeta potentials of suspension samples were measured at room temperature using a Zeta meter 3.0 equipped with a microprocessor unit (Malvern Instrument Zeta Sizer 2000). Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) determined the concentration of the prepared Na2SiO3 solution. The analyses were carried out at FM involving a Varian ICP-MS and a New Wave UP213 laser, for direct introduction of solid samples.

Table 1

XRF analysis for semi-burned rice straw as received.

Table 2 XRF analysis of thermally treated SBRSA with fraction size less than 0.71 mm. Element

Compound formula

Concentration (%)

Na Mg Al Si P S K Ca Ti Mn Fe Cu Zn Sr Pb Cl L.O.I Total

Na2O MgO Al2O3 SiO2 P2O5 SO3 K2O CaO TiO2 MnO Fe2O3 CuO ZnO SrO PbO Cl

1.026 2.729 0.774 82.972 0.267 0.240 2.711 2.528 0.130 0.317 1.571 0.016 0.018 0.023 0.007 0.171 4.500 100.00

Table 3 XRF analysis of silica nano-particles prepared from SBRSA. Element

Compound formula

Concentration (%)

Si Na K Al Fe Total

SiO2 Na2O K2O Al2O3 Fe2O3

99.80 0.110 0.032 0.031 0.015 100.00

Table 4 XRF analysis of SiO2/CaCO3 nanocomposites CS1, CS2 and CS3.

Element

Compound formula

Concentration (%)

Element

Compound formula

Na Mg Al Si P S K Ca Ti Mn Fe Cl L.O.I Total

Na2O MgO Al2O3 SiO2 P2O5 SO3 K2O CaO TiO2 MnO Fe2O3 Cl

1.38 0.14 0.33 62.5 0.26 0.56 1.98 0.91 0.11 0.53 0.37 1.68 29.25 100.00

Na Mg Al Si P S Ca Fe Sr Cl L.O.I Total

Na2O MgO Al2O3 SiO2 P2O5 SO3 CaO Fe2O3 SrO Cl CO2

Concentration (%) CS1

CS2

CS3

0.060 0.188 0.094 1.822 0.012 0.077 54.992 0.247 0.031 0.033 41.894 100

0.061 0.187 0.094 2.123 0.010 0.077 53.822 0.248 0.032 0.043 43.303 100

0.060 0.187 0.094 2.997 0.013 0.075 53.812 0.245 0.032 0.042 42.443 100

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash

Figure 1

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FT-IR spectra of silica nano-particles prepared from thermally treated SBRSA.

Figure 2 FT-IR spectra of CaCO3 core particles (C) and SiO2/CaCO3 nanocomposites prepared at different SiO2:CaCO3 molar ratios 1:15 (CS1), 1:10 (CS2) and 1:5 (CS3).

Figure 3

SEM images of thermally treated SBRSA at magniﬁcations (a) 150· and (b) 350·.

according to Tappi test method T211 om-93. The ﬁller retention (R) was calculated as follows: Retention ¼

X2 X0 :100% X1

ð1Þ

Where: X2 = Ash of paper loaded with ﬁller, X0 = Ash of nonloaded paper and X1 = Ash of added ﬁller. The paper grammage in g/m2 was calculated according to Tappi test method 410.

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F.A. Morsy et al. instrument, A tear tester (L&W 2404) was used according to Tappi 496. All optical tests were qualitative and conducted using integrating reﬂectometer, model JY9800. The instrument has multifunction; it can be used to measure brightness, whiteness, and opacity. The prepared handsheets’ brightness was measured according to ISO 2470:1999. The degree of whiteness was measured according to ISO 11475:1999. The opacity was measured in accordance with ISO 2471:1998. 3. Results and discussion 3.1. XRF chemical analysis

Figure 4 TEM micrograph of silica nano-particles prepared from thermally treated SBRSA.

The thickness was measured based on Tappi 411 using L&W micrometer 51. The density was calculated according to the following equation: d ¼ 1000 G=t

ð2Þ

where: d = density, kg/m3, G = grammage, g/m2, t = thickness, lm. Bursting was measured using Frank GmbH 1882 burst tester according to Tappi 807. Hounsﬁeld H5KS tensile tester was used to measure tensile strength according to Tappi 404. The internal tearing strength was measured on a pendulum type

Figure 5

Table 1 shows chemical analysis of SBRSA sample as received by using XRF analysis. The results show that the percentage of SiO2 is 62.5% and the moisture content is 7.4%. Table 2 represents XRF analysis of thermally treated SBRSA sample. The percentage of silica increased to be 82.9%. The XRF analysis of silica nano-particles indicates that the produced silica has a high purity reaching to 99.8% (Table 3). Table 4 shows that the prepared SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3) have SiO2 contents of 1.82%, 2.12% and 2.99%, respectively. It is found that the amount of SiO2 in the produced composites increased with increasing the concentration of SiO2:CaCO3 molar ratio in the coating process. 3.2. FT-IR spectrum The major chemical groups present in silica nano-particles prepared from thermally treated SBRSA are identiﬁed by the

TEM images of CaCO3 core particles (C) and SiO2/CaCO3 nanocomposites (CS1), (CS2) and (CS3).

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash

Figure 8

Figure 6

Particle size distribution of SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3).

Figure 7

XRD patterns of silica nano-particles prepared from thermally treated SBRSA.

XRD patterns of CaCO3 core particles (C) and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3).

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Figure 9 Zeta Potential versus pH values of CaCO3 core particles (C), silica nano-particles prepared from thermally treated SBRSA and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3).

Table 5

Average crystal size, particle size, particle morphology, silica content and surface charge of SiO2/CaCO3 nanocomposites.

Samples

SiO2: CaCO3 molar ratio Results Av. crystal Particle size Particle morphology SiO2 content (%) Surface charge (mV) size, nm range (nm)

CaCO3 Core

–

SiO2/CaCO3 CS1 1:15 Nano- composite CS2 1:10 CS3 1:5

57.4

30–70

Rhombohedral

17.4

92.9 80.3 80.2

40–80 60–90 70–110

Rhombohedral Sphere-like Spherical

1.82 2.12 2.99

20.2 22.8 28.1

FT-IR spectra as shown in Fig. 1. The broad absorption band at 3455.8 cm 1 and the peak at 1635 cm 1 are due to silanol OH groups and adsorbed water, respectively. The predominant absorbance peak at 1320 cm 1 is due to siloxane bonds (Si–O–Si). The peaks at 1093, 798.3, and 451.2 cm 1 are due to the asymmetric, symmetric and the bending modes of SiO2, respectively (Kamath and Proctor, 1998). Fig. 2 shows the FT-IR spectra of the CaCO3 core nanoparticles and the SiO2/CaCO3 nanocomposites CS1, CS2 and CS3 with SiO2:CaCO3 molar ratios 1:15, 1:10 and 1:5, respectively. There are signiﬁcant absorption peaks due to CO 2 3 group in CaCO3 core particles (C) at 1466.86, 875.13 and 713.66 cm 1, respectively (Nyquist et al., 1997). Because there is no split occurring at the 1465.86 and 875.13 cm 1, one can conclude that the CaCO3 has a calcite structure (standard calcium carbonate infrared spectra). Spectra of SiO2/CaCO3 nanocomposites CS1, CS2 and CS3 reveal that there are absorption peaks at 3441.8, 1638.87, 1077.01, 797.38 and 463.80 cm 1 which conﬁrms the formation of silica (Martinez et al., 1998) besides the absorption peaks of CaCO3, which indicates the presence of both silica and CaCO. The bands at 3441.8 and 1638.87 cm 1 are related to the constitutional water and those at 1086.01, 959.72, 797.38 and 461.34 cm 1 are attributed to the Si–OH stretching, Si–O–Si asymmetric stretching, symmetric stretching and bending vibrations, respectively.

3.3. Morphology and XRD analysis Fig. 3 shows the SEM images of thermally treated SBRSA. It is observed that the ash has black with grey particles as a result of different steps of carbon combustion during the rice straw burning. The micrographs show that the SBRSA has mainly needle-like particles. Fig. 4 shows TEM micrograph of the produced silica. The silica nano-particles have narrow size distribution (particle sizes are ranged from 20–30 nm) with a spherical shape and good dispersion. Fig. 5 shows TEM micrographs of nanoCaCO3 core particles (C) and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3). The nano-CaCO3 core particles have rhombohedral structure with particles size range 30–70 nm. SiO2/CaCO3 nanocomposites CS1, CS2 and CS3 have rhombohedral, sphere-like and spherical morphology, with particle sizes ranging from 40–80, 60–90 and 70–110 nm, respectively. It is noticed that the SiO2/CaCO3 nanocomposites are brighter than those of the single CaCO3 particles. Fig. 6 represents particle size distribution of SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3). Fig. 7 represents X-ray diffraction patterns of silica nanoparticles prepared from SBRSA. It is clear that the typical silica is observed at a broad peak centred at 2h = 22.5 , which indicates that the sample is semi-crystalline phase. Fig. 8 shows XRD patterns of the CaCO3 nano-particles and SiO2/CaCO3

55.7 57.5 60.1 80.2 81.2 82.2 40–80 60–90 70–110 CS1 CS2 CS3 SiO2/CaCO3 nanocomposite

Rhombohedral Sphere-like Spherical

9.68 9.89 10.71

81.66 81 81.45 54.76 53.17 50.44 4.04 3.89 3.82 13.74 13.61 13.38 61.72 60.17 60.24

68.56 67.89 68.19

70.8 78.1 20–30 S Silica

Spherical

11.18

80.47 40.25 2.94 7.75 58.51

65.42

Non 45.5 62.6 76.6 BK PCC References

Non 250 nm 1.5 lm length

Non Scalenohedral

10.02 9.65

72.46 77.97 72.74 54.08 4.68 4.17 14.88 14.47 59.5 60.48

55.5 61.94

Opacity (%) Brightness (%)

Whiteness (%)

Optical Properties

Tensile index N m/g Burst index (kPa m2/g)

Tear index mN m2/g Mechanical Properties

Density (kg/m3) Grammage g/m2

Physical Properties Morphology

Handsheet

Particle size (nm) Symbol Type of ﬁller

Table 6

Fillers characterization

Physical, mechanical and optical properties of reference handsheets and handsheets loaded with nano-silica and SiO2/CaCO3 nanocomposite ﬁllers.

Retention (%)

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash

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nanocomposites (CS1, CS2 and CS3). The results show that all the diffraction peaks of nano-CaCO3 core particles (C) can be related to a pure calcite phase. The SiO2/CaCO3 nanocomposites CS1, CS2 and CS3 samples have similar diffraction peaks which indicate that the shell layer of SiO2 is semi-crystalline. It can be noticed that the intensities of the peaks at 2-Theta Scale at 23 and 29.5 are increased in the case of CS1, CS2 and CS3 compared to CaCO3 core particles (C). The XRD analysis results are in a good agreement with the results obtained from FT-IR. 3.4. Zeta potential Fig. 9 shows the result of zeta potential versus pH values (6– 10) of the produced silica nano-particles, CaCO3 core particles (C) and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3). The result shows that the negative surface charges on the produced silica nano-particles increased gradually to more negative values with increasing the pH value (Tsai, 2004). At pH = 10 zeta potential is 38.4 mV. The results show that zeta potential of CaCO3 core nano-particles at pH = 10 is 17.4 mV, while zeta potentials of the prepared composites CS1, CS2 and CS3 are 20.2, 22.8 and 28.1 mV, respectively. It is observed that zeta potential values of the prepared SiO2/CaCO3 nanocomposites are more negative than core particles and these negative values increased gradually with the increase of SiO2:CaCO3 molar ratio. Table 5 summarizes the obtained results of SiO2/CaCO3 nanocomposites using XRD, TEM, XRF and Zeta potential techniques. 3.5. Properties of handsheets loaded with the prepared nanofillers The physical, mechanical and optical properties of reference handsheets (unloaded and commercial PCC loaded handsheets) and handsheets loaded with silica nano-particles (S), and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3) fillers are summarized in Table 6. 3.5.1. Retention The results shown in Table 6 reveal that silica nano-particles (S) and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3) have a higher retention than the commercial PCC; the percentage of increase reaches 34.9% for silica nano-particles, while it varies from 6.1% to 14.4% for SiO2/CaCO3 nanocomposites. The presence of cationic polyacrylamide enhances silica nano-particles and SiO2/CaCO3 nanocomposite aggregation to optimum size. Agglomerated fillers are sufficiently large in size to be retained within the sheet and fill the fibres’ gaps. The long-chain cationic polyacrylamide adsorption on the surfaces occurs through either bridging or charge neutralization. Charge neutralization occurs in the vicinity of zero potential (i.e., the isoelectric point) where the aggregation of fine particles (i.e., fines, fillers) is at its maximum point since charge neutralization promotes the bridging through depressing the double layer thickness (Khosravani et al., 2010). Silica nanoparticles and SiO2/CaCO3 nanocomposites neutralize the polyelectrolyte charges more aggressively than the other anionic components of pulp stock. Adsorption of silica nano-particles on SiO2/CaCO3 nanocomposite particles screens out repulsive

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Figure 10 SEM images of handsheets loaded with (a) commercial PCC reference, (b) silica nano-particles and (c) SiO2/CaCO3 nanocomposite CS1.

electrostatic interactions between the polymers and the surfaces, thus increasing the adsorption and retention. This result is conﬁrmed by the zeta potential measurements, where silica nano-particles have the greatest retention (70.8%) and the highest zeta potential ( 38.4 mV). The retention of SiO2/ CaCO3 nanocomposites increased as the surface negativity increased in the order CS1 < CS2 < CS3 as shown in Tables 5 and 6. 3.5.2. Physical properties of handsheets 3.5.2.1. Grammage and handsheet density. Table 6 represents the effect of the prepared silica nano-particles and SiO2/ CaCO3 nanocomposites (CS1, CS2 and CS3) on handsheets’ density and grammage at constant pressing action. The results show that silica nano-particles and SiO2/CaCO3 nanocomposites have lower densities than the unloaded sample (BK) and the PCC loaded handsheets. The percentage of density decrease reached 46.5% for silica nano-particles, while the percentage of decrease varied from 5% to 7.5% for SiO2/CaCO3 nanocomposites. Silica nano-particles showed the lowest handsheet density and grammage. This may be due to highest retention and smallest particle size of silica nano-particles (20– 30 nm) than other ones. The higher retention of silica nanoparticles than SiO2/CaCO3 nanocomposites CS1, CS2 and CS3 led to increasing inter-ﬁbre spacing and reducing handsheet density.

The small particle size of nano-filler led to higher relative amount of fibre surface that can be covered by given mass particles which prevents inter-fibre contact over a larger fraction of the available surface area (Hubbe and Gill, 2004). Silica nano-particles showed the lowest handsheet burst index. This may be due to highest retention and smaller particle size of silica nano-particles than the others. Despite the higher retention value of CS1 than commercial pigment, there is no significant decrease in burst index. 3.5.3.2. Tensile index. The results obtained in Table 6 illustrate that addition of silica nano-particles led to a significant decrease in tensile index. This sample has the highest retention (70.8%). Although nanocomposite samples showed higher retention than PCC, acceptable tensile values were obtained. 3.5.3.3. Tear index. Handsheets loaded with silica nano-particles and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3) show higher tear indexes than PCC loaded handsheets (Table 6) the increase reached to 10.9% for CS3 sample. Silica nano-particles show the highest handsheet tear index due to their higher retention and smaller particle size than both SiO2/CaCO3 nanocomposites and PCC. In addition, the tear indexes of SiO2/CaCO3 nanocomposites increased with increasing SiO2 shell thickness. 3.5.4. Optical properties of handsheets

3.5.3. Mechanical properties of handsheets 3.5.3.1. Burst index. Handsheets loaded with silica nano-particles and SiO2/CaCO3 nanocomposites have lower burst indexes than PCC loaded handsheets as shown in Table 6.

Table 6 illustrates the effect of the prepared nano-ﬁllers on optical properties of the handsheets. Silica nano-particles and SiO2/CaCO3 nanocomposites signiﬁcantly improved brightness, whiteness and opacity of the prepared handsheets

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash compared to unloaded (BK) and commercial PCC loaded handsheets. The reasons for these behaviours are the smaller particle size, larger surface and higher light scattering of silica nano-particles and SiO2/CaCO3 nanocomposites (CS1, CS2 and CS3) comparing to micron size of PCC (Hubbe and Gill, 2004).The incident light on SiO2/CaCO3 nanocomposite was refracted on air/silica interface and SiO2/CaCO3 interface, thus led to imparting SiO2/CaCO3 nanocomposites higher refractive indices than CaCO3 alone (Bala et al., 2007). SiO2/ CaCO3 nanocomposites increased the optical properties than silica nano-particles. SiO2 shell thickness has a little effect on brightness and whiteness while it has a significant effect on opacity. In addition, CS3 shows the highest handsheet opacity. The handsheet opacity increased from 4.6% to 7.3% with increasing SiO2 shell thickness from CS1 to CS3, compared with PCC loaded handsheets. This may be due to high retention of CS3 than CS1 and CS2. 3.5.5. Morphology of handsheets Figs. 10 shows the surface of handsheets loaded with commercial PCC reference, silica nano-particles (S) and SiO2/CaCO3 nanocomposite CS1, respectively. Fig. 10a shows bad PCC distribution and more particles were attached on fibre surfaces than on fibre gaps. The high retention of silica nano-particles, high negatively charged surface and the use of high molecular weight polyacrylamide caused aggregation of silica nano-particles as large agglomerates (Fig. 10b). The aggregation of silica nano-particles within paper sheets enhanced optical properties but reduced tensile and burst indexes comparing to commercial PCC as shown in Table 6. Fig. 10c shows that CS1 nanocomposite is uniformly distributed. From the properties of handsheets (Table 6) it was found that the nanocomposite CS1 shows higher mechanical properties than CS2 and CS3. This filler has less negative surface charge and smaller SiO2 shell thickness than CS2 and CS3. Thus, it may be able to form less aggregate particles to cover more fibre surface and densely fill the fibre gaps. 4. Conclusions Silica nano-particles and SiO2/CaCO3 nanocomposite were successfully prepared from sodium silicate solution that was obtained from the semi-burned rice straw ash (SBRSA). The thermal treatment of SBRSA at 800 C for 2 h concentrated SiO2 from 60.2% up to 82.9%. XRD patterns showed that the precipitated silica nano-particles have a semi-crystalline phase and Zeta potential 38.4 mV at pH 10. While the negative surface potential of the prepared nanocomposites changed from 20.2, 22.8 to 28.1 mV with increasing SiO2:CaCO3 molar ratio. TEM images, XRD, FT-IR with zeta potential measurements indicated that the amount of SiO2 increased with increasing SiO2:CaCO3 molar ratio at the coating process. The results showed that the retention of silica nano-particles increased due to the high negatively charged surface which caused aggregation in the matrix. Thus, enhanced optical properties but it slightly reduced mechanical properties comparing to commercial PCC. The retention of the prepared SiO2/CaCO3 nanocomposite also increased with increasing SiO2:CaCO3 molar ratio. On the other hand, the results revealed that the mechanical properties were not significantly

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affected while the handsheet brightness, whiteness and opacity were improved compared to commercial PCC. Acknowledgement This work was supported by Egyptian Science and Technology Development Fund (STDF) under Grant no. ID 737. References Barhoum, A., Rahier, H., Esmail Abou-Zaied, R., Rehan, M., Dufour, T., Hill, G., Dufresne, A., 2014. Effect of cationic and anionic surfactants on the application of calcium carbonate nanoparticles in paper coating. ACS Appl. Mater. Interfaces. 6, 2734–2744. Bala, H., Zhang, Y., Ynag, H., Wang, C., Li, M., Lv, X., Wang, Z., 2007. Preparation and characteristics of calcium carbonate/silica nanoparticles with core-shell structure. Colloids Surf., A 294, 8–13. El-Sheikh, S.M., El-Sherbiny, S., Barhoum, A., Deng, Y., 2013. Effects of cationic surfactant during the precipitation of calcium carbonate nano-particles on their size, morphology, and other characteristics. Colloids Surf., A. 422, 44–49. Gamelas, J.A.F., Lourenco, A.F., Ferreira, P.J., 2011. New modified filler obtained by silica formed by sol–gel method on calcium carbonate. J. Sol-Gel Sci. Technol. 59 (1), 25–31. Gupta N., 2007. Effect of various fillers on physical and optical properties of agro-straw papers, A Master Thesis of Science, School of Physics and Material Sciences. Thapar University Patiala, India. Hall, S.R., Davis, S.A., Mann, S., 2000. Condensation of organosilica hybrid shells on nanoparticle templates: a direct synthetic route to functionalized core-shell colloids. Langmuir 16, 1454–1456. Hubbe, M.A., Gill, R. A., 2004. Filler particle shape vs. paper properties, A review in 2004 TAPPI Paper Summit - Spring Technical and International Environmental Conference in Atlanta, Georgia, May 2–5, 141–150. Kamath, S.R., Proctor, A., 1998. Silica gel from rice hull ash: preparation and characterization. Cereal Chem. 75, 484–487. Khosravani, A., Latibari, A.J., Mirshokraei, S.I., Rahmaninia, M., Nazhad, M.M., 2010. Studying the effect of cationic starch- anionic nanosilica system on retention and drainage. BioResources 5 (2), 939–950. Kim, D.S., Lee, C.K., 2002. Surface modification of precipitated calcium carbonate using aqueous fluosilicic acid. App. Surf. Sci. 202, 15–20. Lattaud, K., Vilminot, S., Hirlimann, C., Parant, H., Schoelkopf, J., Gane, P., 2006. Index of refraction enhancement of calcite particles coated with zinc carbonate. Solid State Sci. 8 (10), 1222–1228. Lourenço, A.F., Gamelas, J.A.F., Zscherneck, C., Ferreira, P.J., 2013. Evaluation of silica-coated PCC as new modified filler for papermaking. Ind. Eng. Chem. Res. 52 (14), 5095–5099. Martinez, J.R., Ruiz, F., Vorobiev, Y.V., 1998. Infrared spectroscopy analysis of the local atomic structure in silica prepared by sol-gel. J. Chem. Phys. 109 (17), 7511–7514. Nyquist, R.A., Putzig, C.L., Leugers, M.A., 1997. In: The Handbook of Infrared and Raman Spectra of Inorganic Compounds and Organic Salts, vol. 1. Academic press, San Diego. Park, J.K., Kim, J.K., Kim, H.K., 2007. TiO2–SiO2 composite filler for thin paper. J. Mater. Prod. Technol. 186 (1–3), 367–369. Shen, J., Song, Z.Q., Qian, X.R., Wang, K.C., Zhang, Y., 2008. Dissolution-inhibiting effect of silicate-based inhibitors on precipitated calcium carbonate filler. China Pulp & Pap. 27 (10), 13–17. Shen, J., Song, Z., Qian, X., Yang, F., Kong, F., 2010. Nanofillers for papermaking wet end applications. BioResources 5 (3), 1328–1331. Smook, G.A., 1997. Handbook for Pulp & Paper Technologists, 2nd edition. Angus Wilde Publications Inc., Bellingham, WA.

1196 Snowden, K. J., Wu, K. T., Rodriguez, J. M., 2000. U.S. Patent 6,083,317, Jul. 4. Tsai, M.S., 2004. The study of formation colloidal silica via sodium silicate. Mater. Sci. Eng., B 106 (1), 52–55. Vestal, C.R., Zhang, Z.J., 2002. Atom transfer radical polymerization synthesis and magnetic characterization of Mnfe2o4/polystyrene

F.A. Morsy et al. core/shell nanoparticles. J. Am. Chem. Soc. 124 (48), 14312– 14313. Zaky, R., Hessien, M., El-Midany, A., Khedr, M., Abdel-Aal, E., ElBarawy, K., 2008. Preparation of silica nanoparticles from semiburned rice straw ash. Powder Technol. 185 (1), 31–35.

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Modeling Warp in Corrugated Cardboard Based on Homogenization Techniques for In-Process Measurement Applications MARKUS BECK & GERHARD FISCHERAUER. A model for describing warp—characterized as a systematic, large-scale deviation from the intended flat shape—in corrugated board based on Kirchhoff plate theory is proposed. It is based on established homogenization techniques and only a minimum of model assumptions. This yields general results applicable to any kind of corrugated cardboard. Since the model is intended to be used with industrial data, basic material properties which are usually not measured in practice are summarized to a few parameters. Those parameters can easily be fitted to the measurement data, allowing the user to systematically identify ways to reduce warp in a given situation in practice. In particular, the model can be used both as a filter to separate the warp from other surface effects such as washboarding, and to interpolate between discrete sample points scattered across the surface of a corrugated board sheet. Applying the model only requires height measurements of the corrugated board at several known (not necessarily exactly predetermined) locations across the corrugated board and acts as an interpolation or regression method between those points. These data can be acquired during production in a cost-efficient way and do not require any destructive testing of the board. The principle of an algorithm for fitting measured data to the model is presented and illustrated with examples taken from ongoing measurements. Additionally, the case of warpfree board is analysed in more detail to deduce additional theoretical conditions necessary to reach this state. Contact information: Faculty of Engineering Science, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany. Appl. Sci. 2022, 12, 1684. https://doi.org/10.3390/app12031684 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 16

Article 5 – Modelling Warp in Corrugated Board

applied sciences Article

Modeling Warp in Corrugated Cardboard Based on Homogenization Techniques for In-Process Measurement Applications Markus Beck *

and Gerhard Fischerauer Chair of Measurement and Control Systems, Faculty of Engineering Science, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany; Gerhard.Fischerauer@uni-bayreuth.de * Correspondence: Markus.Beck@uni-bayreuth.de

Featured Application: The model proposed in this article lays the foundation for cost-efﬁcient inprocess measurement of warp in corrugated cardboard manufacturing and, subsequently, improved process control to reduce waste.

Citation: Beck, M.; Fischerauer, G. Modeling Warp in Corrugated Cardboard Based on Homogenization Techniques for In-Process Measurement Applications. Appl. Sci. 2022, 12, 1684. https://doi.org/

Abstract: A model for describing warp—characterized as a systematic, large-scale deviation from the intended flat shape—in corrugated board based on Kirchhoff plate theory is proposed. It is based on established homogenization techniques and only a minimum of model assumptions. This yields general results applicable to any kind of corrugated cardboard. Since the model is intended to be used with industrial data, basic material properties which are usually not measured in practice are summarized to a few parameters. Those parameters can easily be fitted to the measurement data, allowing the user to systematically identify ways to reduce warp in a given situation in practice. In particular, the model can be used both as a filter to separate the warp from other surface effects such as washboarding, and to interpolate between discrete sample points scattered across the surface of a corrugated board sheet. Applying the model only requires height measurements of the corrugated board at several known (not necessarily exactly predetermined) locations across the corrugated board and acts as an interpolation or regression method between those points. These data can be acquired during production in a cost-efficient way and do not require any destructive testing of the board. The principle of an algorithm for fitting measured data to the model is presented and illustrated with examples taken from ongoing measurements. Additionally, the case of warp-free board is analyzed in more detail to deduce additional theoretical conditions necessary to reach this state.

10.3390/app12031684 Academic Editor: Andrea Dorigato

Keywords: corrugated board; homogenization; orthotropic plate; warping

Received: 29 November 2021 Accepted: 3 February 2022 Published: 6 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁliations.

1. Introduction Despite ubiquity in daily life and high production volume (45 × 109 m2 with 1.6% annual growth in Europe as of 2019 [1]), corrugated cardboard and especially its production receive only a little attention in scientiﬁc research. The existing research is mainly focused on mechanical properties such as buckling under load [2], bending, and torsional and transverse shear stiffness [3]. In [4,5], the effect of partially crushing the corrugated structure—a problem that routinely occurs while printing or otherwise processing corrugated board—on mechanical properties is studied numerically, analytically and with lab tests, while differentiating the structure of the corrugation. This focus on mainly mechanical properties of corrugated board is also present in the standardized testing procedures applied in corrugated board industry. Ref. [6] gives an overview over usual testing procedures, including ﬂat crush test, edge crush test, and tests for puncture and bursting resistance. It should be noted that those tests are designed to destroy the analyzed samples. In [7], the authors provide both a numerical and an analytical model to predict compressive strength, edge crush test, and overall stiffness of

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https://www.mdpi.com/journal/applsci

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corrugated board, and could prove that the much more easily evaluated analytical model reaches the same accuracy as the numerical approach. The most typical product made of corrugated board are boxes for storage and transportation. Therefore, the load-bearing capability of those boxes is also of interest. Ref. [8] provides a review of the research on the load-bearing capability of corrugated board boxes depending of various influence factors (e.g., moisture, holes, or inserts). Recently, a series of articles [9–11] systematically analyzed the influence of various modifications in the basic structure of a standard flap box, namely, the influence of holes, perforations, and offset in the height of the flaps, respectively. Combining numerical finite-element calculations with lab tests, those articles derived improved analytical formulas for estimating the compressive strength of such modified boxes compared to classical and widely used formulas. Production defects such as warping of the board see less research activity. As in the examples above, often the properties of error-free manufactured corrugated board are investigated. Production defects are nonetheless a practical problem: corrugated board that exceeds a certain limit of warp can no longer be reliably processed and must therefore be considered as waste. Ref. [12] describes practical optimizations to reduce warp in production, but does not address the formation of warp within the corrugated board. This article acts as a first step of a more theory-based approach to process control by providing a mathematical model for the description of warp. In order to reduce waste resulting from the production of warped corrugated board, better process control is necessary. This, in turn, requires the possibility of measuring warp in an automated and cost-efficient way; otherwise, accepting a certain amount of warp (and, consequently, waste) can simply be the more economic decision for running a production plant. A possible solution for this problem is to use a low number of cheaply available spot displacement sensors (usually based on laser triangulation) to measure the height at discrete points distributed sparsely over the surface of the corrugated board, and interpolate between those points. This interpolation should represent the form of (warped) corrugated board as closely as possible with a minimum of measured points. Therefore, this article develops a model describing the surface form of warped corrugated board. The knowledge about the physical properties of corrugated board embedded in this model reduces the degrees of freedom which need to be determined from measured data, and, as a consequence, the number of sensors required. This allows automated, cost-efficient, and robust (ignoring small-scale surface defects) measurement of warp in corrugated board manufacturing, providing a previously unattained level of information about the warping of the produced board. In a future step, this information could be used for real-time process monitoring and control. The model proposed in this article expresses warp as a result of internal stress using classical Kirchhoff plate theory. Thereby, the model incorporates knowledge of the physical causes of warp which helps to reduce the number of measure points required for interpolation. In order to maximize the practical utility of the model for analyzing warp in the production process and ultimately provide the necessary measurement tools to dynamically adjust production parameters to reduce warp, no knowledge of the mechanical parameters of the corrugated board is assumed, since those parameters can usually only be obtained by destructive testing. Instead, the number of parameters is reduced as much as possible, allowing reconstruction of the necessary information from the measured data. This model also helps to formalize the concept of warp. Warp is intuitively described as the general trend of the surface over a larger area (as opposed to local fluctuations such as dents or the washboarding effect, which, while also important quality metrics, need to be treated differently in production), a definition which is too vague to actually work with. Figure 1 illustrates the difference between large-scale warp and small-scale surface defects. This means that, even if the exact surface of a corrugated board would be known, the warp would still not be easily quantified. In the corrugated board industry, cumulative values derived from the maximal deviation from an ideal plane are currently routinely used to quantify warp. Ref. [13] calculates the direct quotient between the maximal deflection and

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the width of the board, whereas [14] uses the quadratic width of the board along with a normalization factor to ensure a dimension-free result. While those metrics can serve as a quality feature to distinguish between acceptable and non-acceptable amounts of warp, reducing a surface to a single number neglects a lot of information. This information could otherwise be used to improve the control of the manufacturing process.

Figure 1. Typical production defects of corrugated board. The overall board is warped. The two magniﬁed details show a damaged top liner (I) and washboarding (II). The aim of the presented model is to separate large-scale warping from those (and similar) small-scale effects.

In order to simplify the rather complex structure of corrugated board, homogenization is often applied, among others in [4,5,9–11]. This technique has already been extensively studied and been proven to represent the behavior of various corrugated structures with high accuracy. Literature therefore offers a range of different approximations to calculate the stiffness parameters of an equivalent orthotropic plate from the properties of the base material of corrugated plates. In [15], different homogenization models are compared using finite-element methods. The method proposed in [16] is not only verified with regard to the displacement under load, but also with regard to the internal forces and moments of the board. The approach outlined in [17] is checked for validity in borderline cases, such as a corrugation height of zero, against the respective analytic solutions. In [18], a combination of classical lamination theory and an equivalent energy method is used with a special focus on corrugated laminates. Recently, [19] included the effects of creasing and perforation on stability in homogenization approaches, and [20] derives effective torsional and transversal stiffness parameters for homogenization of corrugated cardboard. The mentioned applications of the homogenization technique are intended to analyze the reaction of corrugated board to external loads. This article, in contrast, focuses on internal stress in order to model warp, which is not covered by the models in the existing literature. In [21], warp in fused deposition modeling (FDM) rapid prototyping is modeled. The basic situation is somewhat similar to corrugated board, as rapid prototyping also works with clearly defined layers. Since workpieces manufactured this way can have arbitrary shape, they cannot be modeled as plates, contrary to corrugated board. This prevents an easy inclusion of forces—namely, their own weight—in the model. Moreover, the model in [21] utilizes the fact that the primary cause of warp in FDM processes, thermal contraction during the cooling phase, can directly be expressed by simple physical relations. The situation in corrugated board is more complex, which forces this article to take a more general approach. 2. Modeling 2.1. General Model Assumptions Corrugated board is produced by gluing together several—usually at least 3—paper sheets (see Figure 2a for an example). Every second sheet is pressed into a corrugated form before gluing it to the flat sheets to form a fluting. Warpage is caused by internal stresses in this composite. Alternatively, these stresses can also be regarded as the result of deformation of individual sheets at the time of gluing in relation to the later state of equilibrium (Figure 3). The reason for this distortion—temperature, humidity, and mechanical prestressing of the sheets would be obvious parameters in the actual production process—is irrelevant for modeling; it is sufficient to note that such a distortion state exists.

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Figure 2. Possible example structure of corrugated board with two (different) ﬂutings (a) and the equivalent orthotropic plate model (b).

Figure 3. Model assumption for the deformation of the individual paper sheets during production (dashed line) compared to the later equilibrium state (solid line). This causes a position-dependent displacement (u,v)T .

The corrugated board is modeled as an orthotropic plate residing in the xy-plane with the corrugation direction aligned to one of the coordinate axes (Figure 2b). The warp is, as mentioned above, the systematic large-scale deviation from the ideal planar form, not including any local defects. It is seen as the result of the internal strain based on linear Kirchhoff theory. This means that the displacement w(x,y) is considered to be small enough to be neglected and all calculations can be performed as if the plate was flat. It should be noted that the approach of this model is to take the well-established homogenization approach for corrugated structures and apply it backwards in a certain sense: as shown in the literature [16–18], it is possible to approximate the overall behavior of a corrugated board by a homogenous, orthotropic plate. Therefore, the proposed model assumes that internal forces, strains, and moments can be approximated as in a homogenous plate as well. Besides the internal stress, the only forces considered are the weight of the board and the reaction forces of the underground. Since the model is intended to be used to characterize warp, it seems reasonable to assume the board to be under measurement conditions with no external loads. The self-weight, however, needs to be included in calculations: while corrugated structures are generally known for providing high stiffness at low specific weight, the size of corrugated boards creates lever arms that can cause visible deformation under the weight of the board. By only considering situations without external loads, the model can be simplified: the board is only under bending load (compression in z-direction can be neglected compared to the warping), while in-plane deformation is not considered. Therefore, extension-bending coupling—which would otherwise be relevant if the board is not symmetric—does not have any effect relevant to the considerations of the article and can thus be neglected. Since there are no external in-plane forces, classical buckling is not included in the model. The compressive forces for buckling must stay in plane while the plate is deformed

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so that a lever arm exists within the deformed plate. The internal forces discussed here, however, will always be aligned with the plate. The in-plane deformation of the board is neglected since it is, contrary to warpage, not relevant in industrial practice. For the rest of this section, the relevant equations for modeling orthotropic Kirchhoff plates under orthogonal surface load are summarized based on standard textbook knowledge (e.g., [22] (pp. 193–208)). It is important to note here that the subsequent equations refer to an orthotropic plate, which would show the same reaction as the corrugated board to a pure bending load; the equivalent material parameters used here cannot be used to describe in-plane deformation. The stress–strain relation of an orthotropic material within a plane is: ⎛ ⎞ ⎛ ⎞ ⎞ ⎛ σx E1 E2 0 εx ⎝ σy ⎠ = ⎝ E2 E4 0 ⎠ · ⎝ ε y ⎠. (1) τxy γ 0 0 G As usual, σ∗ , and τxy denote the normal and shear stress, respectively (with the orientation given in the index), ε ∗ and γ normal and shear strain, and the matrix includes the elastic parameters of the material. Under the assumptions of Kirchhoff theory, the strain is approximated from the deﬂection w by: ∂2 w , ∂x2 ∂2 w ε y = −z · ∂y2 , ∂2 w γ = −z · ∂x∂y .

ε x = −z ·

(2)

The moments in a plate of thickness t (aligned with the z-coordinate as shown in Figure 2b) are given by integrals over the stresses: Mx ( x, y) =

t/2

My ( x, y) = Mxy ( x, y) =

−t/2 σx ( x, y, z ) · zdz,

t 2 −t 2 t 2 −t 2

σy ( x, y, z) · zdz,

(3)

τxy ( x, y, z) · zdz,

Note that Equation (3) is derived by analyzing an inﬁnitesimal section of the plate. The moments are therefore given per length of the section plane and appear to have the unit of forces. One would obtain the actual moments by integrating the terms above over the length of the respective edge Inserting the relations (2) yields: 3 2 2 Mx ( x, y) = −12t · E1 · ∂∂xw2 + E2 · ∂∂yw2 3 2 2 (4) My ( x, y) = −12t · E2 · ∂ w2 + E4 · ∂ w2 ∂x

Mxy ( x, y) =

− t3 12

·G·

∂y

∂2 w ∂x∂y

From the equilibrium of forces over an inﬁnitesimal element, one obtains: ∂2 Mxy ∂ 2 My ∂2 M x +2· + = − p( x, y) 2 ∂x∂y ∂x ∂y2

(5)

Here, p denotes the surface load of the plate, which consists of the weight of the board and the reaction forces of the underground, as stated above. Combining these equations leads to the behavior of plates under external forces without any internal stress and therefore without warp.

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2.2. Effects of Internal Stress Equation (4) is usually used to describe the moments and, in combination with (3), the stresses in a plate deformed by external forces. The linearity of Kirchhoff theory allows use of the (negative) internal stresses of the flat plate instead: the deformation by external forces that would cause exactly the negative stress values in a plate without internal stress leads to a compensation and therefore a relaxed state in a plate with internal stresses. The proposed model approximates the corrugated board as a homogenous orthotropic plate; however, internal stress must ultimately be introduced by the paper sheets, which are of negligible thickness compared to the board. Therefore, the relationship between the corrugated board and the idealized plate model needs to be analyzed. For the non-corrugated layers of paper (liners), the stress value at their respective z-positions in the plate is simply the stress introduced in the paper during production. In the case of fluting, the situation seems to be more complex, as their z-position is a function of the location in the xy-plane. However, the warp which is to be modeled here is by its definition the average effect on larger scales. It is therefore reasonable to assume that there is an average z-position for each corrugated layer which sees the stress of this layer. This average position does not need to be the arithmetic mean; the important point is that, for all layers of paper, there exists a z-position within the equivalent orthotropic plate at which the internal stress of the paper is equal to the stress in the orthotropic plate. At this point, the internal stress σI,∗ ( x, y, zi ) at n different z-positions zi is known, where n denotes the number of paper layers in the corrugated board. Since the equations for the three components are identical in principle, σI,∗ is used to represent σI,x , σI,y , or τI,xy . The additional index I denotes quantities resulting from internal stress. Between the positions zi , some kind of interpolation must exist. For this model, we will assume that the interpolation can be written as: σI,∗ ( x, y, z) = −

∑

k =1

f k (z) · σI,∗ ( x, y, zk )

(6)

where f k (z) can be chosen from all functions which satisfy the condition f k ( zl ) = δkl with the Kronecker symbol δkl . While this condition may seem to be trivially satisﬁed, it is important to note that f k ( z) is required to be independent of the coordinate in the xy-plane. This would be natural to assume for an inﬁnite uniform plane, where there is no physical difference between two different points. Therefore, it can be seen as a way of neglecting boundary effects. In other words, this means that the stress in any height can be expressed as a (heightdependent) linear combination of the stress values in the paper planes. This assumption is reasonable, as the entire theory is based on linear material properties. Inserting this interpolation approach into the (internal) moment equations yields: MI,∗ =

t/2

∑ −t/2

k =1

f k (z) · σI,∗ ( x, y, zk ) · z dz =

∑ σI,∗ (x, y, zk ) ·

k =1

t/2 −t/2

f k (z) · z dz.

(7)

As seen here, the expression for the moment can be separated into a position-dependent and a position-independent part. By substituting: κ k :=

t/2

f k (z) · z dz,

(8)

∑ σI,∗ (x, y, zk ) · κk .

(9)

−t/2

one can rewrite the equation as: MI,∗ ( x, y) =

k =1

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This means the moments in the equivalent orthotropic plate can be modeled as a linear combination of the stresses in the individual paper sheets. The same moments and therefore the same bending could also be realized with a linear stress gradient along the z-axis: (10) σI,∗ ( x, y) · z. σI,∗ ( x, y, z) := σI,∗ , as deﬁned here, is given in a unit of stress per height. The respective Note that moment would be: MI,∗ ( x, y) =

t/2 −t/2

σI,∗ · z2 dz =

t3 ! σI,∗ = · 12

∑ σI,∗ (x, y, zk ) · κk .

(11)

k =1

σI,∗ between the top and the bottom Hence, the total difference in the stress per height side of the corrugated board (with an assumed linear stress gradient) can be expressed as: σI,∗ =

∑ σI,∗ (x, y, zk ) ·

k =1

12 · κk . t3

(12)

Combining this result with the moments caused by bending under external forces (4) yields: 2 2 t3 σI,x − E1 · ∂∂xw2 + E2 · ∂∂yw2 , · Mx ( x, y) = 12 2 2 t3 My ( x, y) = 12 σI,y − E2 · ∂∂xw2 + E4 · ∂∂yw2 , (13) · 3 2 t ∂ w Mxy ( x, y) = 12 . · τ I,xy − G · ∂x∂y σI,∗ do not necessarily appear in real corrugated board, Note that, while the quantities they can still be used as a measure of the effective stress as defined by (12). 2.3. Eliminating Excess Degrees of Freedom Thus far, the modeling was focused on the stresses within the paper sheets. However, those stresses were initially assumed to be introduced by a deformation of the respective T sheets at the time of production. This means the three-dimensional stress field σx , σy , τxy is caused and therefore completely described by the two-dimensional displacement field (u,v)T (see Figure 3). Thus, it is important to note that the strain components (and therefore also the stress components) are not independent from each other, but can be derived by: ∂v 1 ∂u ∂v . (14) ε x = ∂u ∂x , ε y = ∂y , γ = 2 ∂y + ∂x The displacement fields are again properties of the individual paper sheets. The linearity of the approach allows use of Equation (1) and to easily insert the different I, v displacements (ui , vi ) T or alternatively the displacement differences per height (u I )T , of an equivalent linear gradient, defined analogously to Equation (10): 1 · ∂u I − ∂2 w2 + E 2 · ∂ vI − ∂2 w2 Mx ( x, y) = E ∂x ∂y ∂x ∂y ∂u I ∂ vI ∂2 w ∂2 w My ( x, y) = E2 · ∂x − ∂x2 + E4 · ∂y − ∂y2 (15) 2 · 1 · ∂uI + ∂ vI − ∂ w Mxy ( x, y) = G 2 ∂y ∂x ∂x∂y Since the effective material parameters for the homogenized orthotropic plate already depend on the geometric details of the corrugation, the leading factors are combined with : = G · t3 . ∗ := E∗ · t3 and G those parameters by substituting E 12 12 Inserting this into the equilibrium of forces (5) results in: 3 3 3 4 3 4 4 ∗ ∂ u I + ∂ v I − 2 · ∂ w 4 ∂ v I − ∂ w = − p (16) 1 ∂ u I − ∂ w + G E + E ∂x3 ∂x∂y2 ∂x2 ∂y ∂x2 ∂y2 ∂y3 ∂x4 ∂y4

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with:

∗ := E 2 · G. G

(17)

This means the corrugated board behaves identically to a board with a different shear ∗ but without the influence of transverse contraction. modulus G In this alternative material, the moments would be: 1 · ∂u I − ∂2 w2 , Mx∗ ( x, y) = E ∂x ∂x ∂ vI ∂2 w ∗ My ( x, y) = E4 · ∂y − ∂y2 , (18) 2 ∗ ( x, y ) = G ∗ · 1 · ∂u I + ∂ vI − ∂ w . Mxy 2 ∂y ∂x ∂x∂y The Equations (16) and (18) can be used to analyze warp from measured data. In order to do this, only three effective material parameters and the effects of production parameters on three effective displacement variables need to be fitted. 2.4. A Condition for Warp-Free Corrugated Board Since the aim of corrugated board production is to eliminate warp, the case w ≡ 0 is analyzed in more detail. If this board is supported by an equally flat surface, the area weight and the reaction forces of the underground compensate each other, so (16) is simplified to: 3 ∗ · 1 · ∂ u I ( x, y) + G E ∂x3

∂3 u I ( x, y) ∂3 v I ( x, y) + ∂x∂y2 ∂x2 ∂y

∂3 v I ( x, y) + E 4 · = 0. ∂y3

(19)

only occurs as a derivative of x and v Obviously, u only as a derivative of y: any constant part of the displacement function is merely a coordinate transformation, which u I vI does not cause any physical effects. Therefore, substituting and ε I,x = ∂∂x ε I,y = ∂ ∂y in accordance with (14) yields: 2 ε ( x, y ) 2 ε ( x, y ) ∂2 ∂2 ε I,y ( x, y) ε I,y ( x, y) I,x I,x ∗ · ∂ ∗ · 4 · 1 · ∂ E E + + + = 0, G G ∂x2 ∂y2 ∂x2 ∂y2

∂2 ∂x2

∂2 ∂y2

∗ G 4 E

1 E G∗

(20)

ε I,x ε I,y

= 0.

(21)

Using the principal-axis transformation (the parameter α simply denotes the ratio between the principal values, allowing a further simpliﬁcation of the equations later): ∗ ∗ 1 G E 0 E T =S S (22) ∗ E 4 0 α · E∗ G

with: S=

cos( ϕ) −sin( ϕ)

sin( ϕ) cos( ϕ)

(23)

the equation is further simpliﬁed:

∂2 ∂x2

∂2 ∂y2

1 0

0 α

ε I,x ( x, y) = 0. S ε I,y ( x, y)

(24)

It should be noted that this transformation is only applied for mathematical reasons: due to the structure of the matrix in Equation (21), there must be a rotation matrix (23) which satisﬁes Equation (22). That means that, in a rotated coordinate system:

η ξ

x y

(25)

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the condition for warp-free corrugated board can be written as: ∂2 ε I,η (η, ξ ) ∂2 ε I,ξ (η, ξ ) +α· = 0. 2 ∂η ∂ξ 2

(26)

This equation only defines the higher-order terms of the strain functions. The linear and constant terms are defined by boundary conditions. The strain components orthogonal to the edge must disappear at the boundaries. Otherwise, there would be forces orthogonal to the edges and the equilibrium of forces would be violated, as the model assumes no external forces. The condition (26) for warp-free corrugated board seems surprisingly simple. The material is effectively reduced to only two parameters α and ϕ. However, the equation must be fulfilled for all points of the surface. This means that the strain along the η- and ξ-axes must be proportional by a fixed factor α to each other. The only exceptions are linear and constant terms, which are, however, completely defined by the boundary conditions. Since corrugated board is produced in a continuous process, it has two clearly distinct directions. In machine direction (aligned with the fluting, coordinate axis y in Figure 2), the individual sheet is cut from a quasi-infinite band, while the width in cross direction (orthogonal to machine direction, coordinate axis x in Figure 2) is limited by the width of the machines. Therefore, it is difficult to imagine a way of matching the strains in two orthogonal axes in practice by influencing production parameters. The only practical way to satisfy (26) seems to be a completely strain-free board, i.e., ε I,η ≡ 0 and ε I,ξ ≡ 0. 3. Applying the Model on Measured Surface Data The primary intended use for the proposed model is the post-processing of measured surface data. This allows both the interpolation of the surface and the separation of warp and other surface defects which are not caused by warp. The basic idea, as shown ∗ , the surface load p, and the effective dis 1/4 , G in Figure 4, is to fit the parameters E T placement field (u, v) ( x, y)—together called “displacement and stiffness parameters” in Figure 4—so that the surface geometry predicted by the model matches the surface height, → measured at defined sample points and stored in order in a measurement vector m (“Measured data at sample points”). While the location of those sample points in the xy-plane must be known, the method proposed here does not depend on a specific sample pattern (e.g., rectangular grid), although the location will influence the numerical precision. The outer loop (consisting of everything in Figure 4 outside of the grey area) follows the general principle of regression by quadratic error minimization, where an optimizer tries to find an input to an abstract function block (the grey area in Figure 4) in order to minimize the quadratic difference between the output of this function block and some external value (in this case, the measured data).

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Figure 4. Application of the model to interpret measured data. A least-square fit is used to find the effective material parameters and displacement fields that provide the best explanation for the observed data. Note that this diagram only displays the principal data flow between separate logical modules needed to apply the model to measured data. The optimization algorithm (“Optimizer”) implements the main control flow (including, e.g., termination conditions when the desired level of precision is needed), utilizing the bending model to evaluate its cost function.

To achieve this, the model (16), denoted as “Bending model” in Figure 4, is used to predict the deformed surface using a mesh-free Ritz–Galerkin approach (the implementation used here follows largely the simple textbook approach as explained, for example, in [23] and would most likely provide room for improvements). It should be noted that, although this step is only shown as an arrow in Figure 4, it requires an iterative algorithm to calculate the parameters deﬁning the surface (“Functional surface description” in Figure 4). This →

prediction step is seen as a function F mapping the parameters mentioned previously to a vector of the expected surface heights at given sampling points. The final step of this mapping (“Virtual sampling” to generate “Predicted heights at sample points” in Figure 4) is a simple evaluation of the functional surface representation defined by the parameters at the known sampling points. → The displacement field is numerically represented by the vector of coefficients q of a polynomial approximation. The surface load consists of the weight of the board and the reaction forces at the points where the corrugated board is in contact with the underground. The board weight is assumed to be equally distributed in the xy-plane, neglecting the fact that sloped areas contain more board per projected area. This approximation greatly simplifies the problem and is consistent with the small deformation assumption needed for the linearity of Kirchhoff theory. The contact forces are determined at discrete points distributed in a regular grid across the board. An elastic contact model is used, i.e., the contact forces compress the board by a small amount, following Hooke’s Law. However, the contact forces result in nonlinear behavior, since they cannot become negative but stay equal to zero once the board lifts of the ground at a specific point (the contact force is proportional to −w · H (−w) where H (·) denotes the nonlinear Heaviside step function and w the displacement). This means that the model must be solved as a non-linear system. →

In practice, this function F (which, as deﬁned above, maps the effective properties of the board to the surface form) has no analytic representation, and evaluating it represents a numerical workload noticeable on a typical desktop computer. However,

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deﬁning this function allows calculation of the initially unknown parameter as solution to a minimization problem: → → ∗ , → 1 , E 4 , G argmin F E q −m

∗ ,→ 1 ,E 4 ,G E q

2 2

(27)

This problem can be solved using a gradient descent algorithm, where the gradient can, if necessary, be approximated numerically using a simple difference quotient. This approach allows use of (16) directly, where parameters describing both the base materials and the detailed structure of the corrugation have been aggressively summarized to a few effective constants, without any need to further analyze the detailed structure of the board. This also includes the interpolation functions f k (z) as introduced in (6) and their integrals κk as defined in (9): only the weighted sums of the displacements in the individual sheets are used; therefore, the mere existence of the interpolation functions or the coefficients κk is sufficient for the numerical application. A detailed analysis of a specific corrugation structure could of course be used to reconstruct the interpolation functions in order to gain additional insight into inner effects within the corrugated board; this is, however, not the aim of this work. In fact, due to the normalizations and substitutions applied, the displacement fields calculated internally by the numerical implementation are represented in units of measurement which are implicitly defined by the properties of the analyzed corrugated board and would therefore be hard to analyze. 4. Comparison with Measured Surfaces Samples taken from the production process of a commercial corrugated board plant were measured with optical triangulation sensors. The shape of the surface was then approximated based on the proposed model, where the displacement functions were limited to quadratic polynomials in machine direction and cubic polynomials in crossdirection. Since the polynomial parameters describing the displacement functions need to be determined from the measurement data, the aim is to choose the lowest possible order without seriously reducing the quality of the fit. Needlessly increasing the number of degrees of freedom could lead to overfitting and increase the impact of measurement noise on the result; moreover, the number of measurement points required would be increased. Therefore, the entire model presented in this article is focused on reducing the number of parameters. Two examples (size of the boards 1884 × 770 mm and 1430 × 1040 mm, respectively) from ongoing research are presented in Figure 5. While boards were obtained from a commercial production plant, they would have been considered waste due to the amount of warp present. The surface defined by the model (displayed as continuous, colored surface in the plots) shows the same shape as the measured data points (black circles in the plots) on a larger scale, while smoothing local variations. The interpolation capability of the model is shown by the fact that only a 6 × 6 grid of measured data points (highlighted as red crosses in Figure 5) was used as input to the fitting algorithm, while the other data points were reserved to verify the results. Some slight systematic deviation from the data can be seen near the edges of the board, which are most likely caused by the numerical solver for the differential Equation (16). The histograms in Figure 5 show the deviation between the measured points and the surface defined by the proposed model, with most of the data points only deviating by a few millimeters (95% of the measured data points are within 2.6 mm and 2.9 mm, respectively, of the reconstructed surfaces in the examples) from the model surface. Since, as seen in the 3D plots, the model surface reproduces the large-scale deformation of the corrugated board—in other words, the warp—the remaining deviations can be seen as being part of the noise when analyzing or controlling warp.

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Figure 5. Examples for surface forms deﬁned by the proposed model (continuous surface), compared to measured data of corrugated board (black circles). Histograms of the distance between the model surface and the measured data are also provided. MD refers to the machine direction, CD the cross direction of corrugated board production.

5. Discussion The model proposed in this article does not contain any assumptions about the inner structure of the board. Therefore, it is applicable to any corrugated board regardless of the number of layers or the form of the corrugation. The only relevant model assumptions are the validity of the homogenization approach and the assumption of a positionindependent interpolation function. The homogenization has already been proven as a good approximation in numerous previous publications. For the second assumption, the position-independent interpolation, arguments were provided in this work. This generality comes at the cost that no calculation method for the linear factors κk can be given at this level of abstraction. The main result is the existence of a linear relationship between the displacement fields in the paper sheets and the curvature caused by the internal stress. While this result may seem weak, a complete functional relationship would probably offer only little additional benefit for the actual industrial practice. The necessary material data are not routinely measured in corrugated board production. Therefore, it appears to be a better approach to fit the linear factors directly to the measured curvatures as outlined in Section 3, especially since there are only three effective parameters in (16). The fact that the curvature depends on a linear combination of the displacements in the individual paper sheets implies that there must be more than one solution for eliminating warp in corrugated board. Only a weighted sum of all paper sheets occurs in the final equations, which means that in theory any effect can be accomplished by influencing only one layer. This seems plausible, as it would otherwise be hard to imagine how warp could be controlled in practice. Many plants rely completely on heuristics and experience of their employees to correctly balance the production parameters (various

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temperatures, moisture, prestressing, etc.). This would hardly be possible if there were only one solution which results in good (i.e., warp-free) corrugated board within the space of possible production parameters. Note that this does not contradict the conclusion drawn from Equation (26), which was that the equivalent strains must completely disappear for the board to be warp-free. The equivalent strains in (26) that must disappear are still linear combinations of the strains in the individual paper sheets, and the latter are directly and individually influenced by production parameters. Establishing an analytic relationship between the displacement in the paper sheets and the curvature also allows inclusion of knowledge about the production process. Assume, for example, that there are a certain number of nozzles installed in the machine to moisturize the paper for processing. Then, moisture in the paper and therefore the displacement caused during subsequent drying, can only have a certain number of degrees of freedom. A simple but general approach is to model the displacement functions as polynomials of a low degree, which was successfully done in the examples in Section 4. As mentioned above, the board is produced in a continuous process. In machine direction, the individual sheet can therefore be seen as a local approximation similar to a Taylor series approximation, since control of production parameters varies only slowly compared to the production speed. In cross-direction, there are a limited number of devices interacting with the paper sheets. As long as this number is sufficiently low to prevent numerical instabilities, a simple polynomial interpolation in-between will probably yield acceptable results. Therefore, a practical approach can model the displacement with a quadratic or cubic polynomial in machine direction and a polynomial of degree three-to-five in cross-direction. This reduction to a limited number of degrees of freedom can also serve an important role for measuring warp. Not every deviation of the real surface of corrugated board is caused by warp. As mentioned above, warp is large-scale, systematic curvature. In reality, however, warp cannot be measured directly. The only quantity which can be measured directly is the shape of the surface. Here, other effects, such as washboarding (where the surface partially follows the form of the fluting), or simple surface defects such as dents, superimpose the warp. Therefore, when combined with a suitable approximation for the technically plausible displacements in the paper sheets, this model can serve as a definition to separate the warp from other effects. Everything that can be explained by the model with displacement functions taken from a sensible function space is considered to be warp and effects of the self-weight (which can be separated by the model, if required). Therefore, to analyze warp, the measured surface data would be fitted to the model, yielding a smooth idealized surface, which in turn can be used to improve process control. 6. Conclusions In this article, a novel method for modeling warp in corrugated cardboard has been developed. This allows more insight into both measurement and control of warp during the production of corrugated board. It gives a more detailed mathematical description of warp than the metrics currently used in the industry. The latter generally reduce the entire effect of warp to a single number, whereas the proposed model allows reconstruction of a 2D surface even from a limited number of sample points. At the same time, the results of applying the model are different from a simple surface scan of the corrugated board (using, e.g., a coordinate-measuring machine), since the latter would also include other surface defects (such as washboarding) which have different reasons and therefore need to be treated differently. The model, on the other hand, can act as a filter extracting the warp selectively, by implicitly defining a set of physically plausible surface forms for warped corrugated board. The model does not require knowledge of the material parameters or the details of the corrugated structure, which makes it easily applicable in industrial production and processing of cardboard, as the mechanical properties are usually measured using destructive tests and, due to the nature of the raw materials, subject to variations even

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between seemingly similar batches. Instead, the model is reduced to a minimal set of parameters, which can be recovered from measurement data via least-square fits as outlined in Section 3. The examples presented in Section 4, taken from ongoing research, illustrate the possibility in principle of applying the model to real-world data. Detailed analysis of the optimal application of the model, including optimal selection of sample points and the achievable measurement uncertainty, remain open for future research. While the model-based approach is applicable with only a minimal set of sensors, it trades those savings in hardware cost for an increased computational load. An efficient implementation of the necessary algorithms is crucial for any practical application, and even then, a real-time evaluation of every single corrugated board produced may not be feasible. Moreover, any model-based approach requires that the model assumptions are satisfied. Sharp bends in the board, for example, would most likely yield unpredictable results, as this is not included in the model. Furthermore, the board should not be too small, since the model neglects border effects. In regard to controlling warp in production, Section 2.4 derives the necessary condition for warp-free board. It is shown that, in theory, an infinite number of possible solutions to correct any given form of warp exists. This opens up the possibility of considering other criteria relevant in industrial corrugated board production, such as energy consumption and production speed. Supplementary Materials: The data displayed in Figure 5 is available online at https://www.mdpi. com/article/10.3390/app12031684/s1 as MATLAB files. Author Contributions: Conceptualization, G.F. and M.B.; methodology, M.B.; software, M.B.; formal analysis, M.B.; writing—original draft preparation, M.B.; writing—review and editing, G.F. and M.B.; visualization, M.B.; supervision, G.F.; project administration, G.F.; funding acquisition, G.F. All authors have read and agreed to the published version of the manuscript. Funding: This work was supported by the ZIM Program (Grant ZF4152307PO8) by the German Federal Ministry for Economic Affairs and Energy. Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—491183248. Funded by the Open Access Publishing Fund of the University of Bayreuth. This Project is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) on the basis of a decision by the German Bundestag. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are available in Supplementary Material. Conflicts of Interest: The authors declare no conflict of interest.

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European Federation of Corrugated Board Manufacturers (FEFCO). Annual Statistics 2019; The European Federation of Corrugated Board Manufacturers: Brussels, Belgium, 2020. Available online: https://www.fefco.org/sites/default/files/documents/Fefco_ AnnualEvaluation_2019.pdf (accessed on 21 August 2020). Biancolini, M.E.; Brutti, C. Numerical and experimental investigation of the strength of corrugated board packages. Packag. Technol. Sci. 2003, 16, 47–60. [CrossRef] Lu, T.J.; Zhu, G. The Elastic Constants of Corrugated Board Panels. J. Compos. Mater. 2001, 35, 1868–1887. [CrossRef] Gajewski, T.; Garbowski, T.; Staszak, N.; Kuca, M. Crushing of Double-Walled Corrugated Board and Its Influence on the Load Capacity of Various Boxes. Energies 2021, 14, 4321. [CrossRef] Garbowski, T.; Gajewski, T.; Mrówczyński, D.; J˛edrzejczak, R. Crushing of Single-Walled Corrugated Board during Converting: Experimental and Numerical Study. Energies 2021, 14, 3203. [CrossRef] European Federation of Corrugated Board Manufacturers (FEFCO). Introduction to the Development of FEFCO Testing Methods for Corrugated Board and Boxes. Available online: https://www.fefco.org/sites/default/files/documents/import_anglais.pdf (accessed on 10 October 2018). Garbowski, T.; Grabski, J.K.; Marek, A. Full-Field Measurements in the Edge Crush Test of a Corrugated Board—Analytical and Numerical Predictive Models. Materials 2021, 14, 2840. [CrossRef] [PubMed] Frank, B. Corrugated Box Compression-A Literature Survey. Packag. Technol. Sci. 2014, 27, 105–128. [CrossRef]

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Garbowski, T.; Gajewski, T.; Grabski, J.K. Estimation of the Compressive Strength of Corrugated Cardboard Boxes with Various Openings. Energies 2021, 14, 155. [CrossRef] Garbowski, T.; Gajewski, T.; Grabski, J.K. Estimation of the Compressive Strength of Corrugated Cardboard Boxes with Various Perforations. Energies 2021, 14, 1095. [CrossRef] Mrówczyński, D.; Garbowski, T.; Knitter-Piaatkowska, ˛ A. Estimation of the Compressive Strength of Corrugated Board Boxes with Shifted Creases on the Flaps. Materials 2021, 14, 5181. [CrossRef] [PubMed] Keyser, R.; Jordan, L. ADDRESSING CORRUGATED BOARD WARP WITH A 23 FACTORIAL DESIGN. J. Manag. Eng. Integr. 2020, 13, 20–31. The International Development Group for Corrugated Board (SUW). Standard for Corrugated Board for Use in Packing Machines; RISE Research Institutes of Sweden: Göteborg, Sweden, 2016. Available online: https://www.ri.se/sites/default/ﬁles/2019-12/ 16.12.20%20English%20SUW%20standard.pdf (accessed on 17 November 2021). European Federation of Corrugated Board Manufacturers (FEFCO). FEFCO Recommendation No. 110; The European Federation of Corrugated Board Manufacturers: Brussels, Belgium, 2018. Available online: http://www.fefco.org/sites/default/ﬁles/2018-1002_FEFCO%20Recommendation%20N110%20Warp%20Factor%281%29.pdf (accessed on 10 October 2018). Nguyen-Minh, N.; Tran-Van, N.; Bui-Xuan, T.; Nguyen-Thoi, T. Static analysis of corrugated panels using homogenization models and a cell-based smoothed mindlin plate element (CS-MIN3). Front. Struct. Civ. Eng. 2019, 13, 251–272. [CrossRef] Xia, Y.; Friswell, M.I.; Flores, E.S. Equivalent models of corrugated panels. Int. J. Solids Struct. 2012, 49, 1453–1462. [CrossRef] Ye, Z.; Berdichevsky, V.L.; Yu, W. An equivalent classical plate model of corrugated structures. Int. J. Solids Struct. 2014, 51, 2073–2083. [CrossRef] Cheon, Y.-J.; Kim, H.-G. An equivalent plate model for corrugated-core sandwich panels. J. Mech. Sci. Technol. 2015, 29, 1217–1223. [CrossRef] Garbowski, T.; Knitter-Piatkowska, ˛ A.; Mrówczyński, D. Numerical Homogenization of Multi-Layered Corrugated Cardboard with Creasing or Perforation. Materials 2021, 14, 3786. [CrossRef] [PubMed] Garbowski, T.; Gajewski, T.; Grabski, J.K. Torsional and Transversal Stiffness of Orthotropic Sandwich Panels. Materials 2020, 13, 5016. [CrossRef] [PubMed] Wang, T.-M.; Xi, J.-T.; Jin, Y. A model research for prototype warp deformation in the FDM process. Int. J. Adv. Manuf. Technol. 2007, 33, 1087–1096. [CrossRef] Gross, D.; Hauger, W.; Wriggers, P. StatikspeziellerTragwerke. In TechnischeMechanik 4; Gross, D., Hauger, W., Wriggers, P., Eds.; Springer: Berlin/Heidelberg, Germany, 2018; pp. 157–209. ISBN 978-3-662-55693-1. Hackbusch, W. Theorie und Numerik Elliptischer Differentialgleichungen; Springer Spektrum: Wiesbaden, Germany, 2017; pp. 163–165. ISBN 978-3-658-15357-1.

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

The CirCo (Circular Coffee) Project: A Case Study on Valorization of Coffee Silverskin in the Context of Circular Economy in Italy 1 2 2 3 EMILY OVERTURF , SIMON PEZZUTTO , MARTINA BOSCHIERO , NICOLETTA RAVASIO & ACHILLE 4 MONEGATO .

Coffee silverskin (CSS) is one of the main byproducts of coffee roasting and poses a potential risk to the environment if disposed of incorrectly. Each year in Italy, over 500,000 tonnes of green coffee are imported for roasting followed by consumption or export. This results in over 7500 tonnes of CSS produced each year which is typically disposed of as solid waste. Silverskin contains lignocellulose and can be used as a substitute for other raw materials to produce paper pulp. Both Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) were performed to compare the impact and cost of CSS paper production to conventional paper production using only virgin pulp. It was shown that the addition of CSS reduces the environmental impact of paper production by 10% and greenhouse gas (GHG) emissions by 13% compared to conventional production with no cost increase (0.01% reduction with addition of CSS) for the producer. The results of this case study show that the utilization of CSS for paper production at the national level in Italy represents a suitable example of circular economy (CE). Contact information: 1 School of Life Sciences, Technical University of Munich,Weihenstephaner Steig, 2285354 Freising, Germany. 2 Institute for Renewable Energy, European Academy of Bolzano (EURAC Research), Viale Druso 1, 39100 Bolzano, Italy. 3 CNR-SCITEC, via C. Golgi 19, 20133 Milan, Italy. 4 FAVINI srl, via Alcide De Gasperi 26, 36028 Rossano Veneto, Italy. Sustainability 2021, 13, 9069. https://doi.org/10.3390/su13169069 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 18

Article 6 – Coffee Silverskin as Pulp

sustainability Article

The CirCo (Circular Coffee) Project: A Case Study on Valorization of Coffee Silverskin in the Context of Circular Economy in Italy Emily Overturf 1 , Simon Pezzutto 2, * , Martina Boschiero 2, *,† , Nicoletta Ravasio 3 and Achille Monegato 4 1

3 4

* †

Citation: Overturf, E.; Pezzutto, S.; Boschiero, M.; Ravasio, N.; Monegato, A. The CirCo (Circular Coffee) Project: A Case Study on Valorization of Coffee Silverskin in the Context of Circular Economy in Italy. Sustainability 2021, 13, 9069.

School of Life Sciences, Technical University of Munich, Weihenstephaner Steig, 2285354 Freising, Germany; emily.overturf@tum.de Institute for Renewable Energy, European Academy of Bolzano (EURAC Research), Viale Druso 1, 39100 Bolzano, Italy CNR-SCITEC, via C. Golgi 19, 20133 Milan, Italy; nicoletta.ravasio@scitec.cnr.it FAVINI srl, via Alcide De Gasperi 26, 36028 Rossano Veneto, Italy; Achille.Monegato@favini.com Correspondence: simon.pezzutto@eurac.edu (S.P.); martinaboschierob@gmail.com (M.B.) Former collaborator of EURAC Research.

Abstract: Coffee silverskin (CSS) is one of the main byproducts of coffee roasting and poses a potential risk to the environment if disposed of incorrectly. Each year in Italy, over 500,000 tonnes of green coffee are imported for roasting followed by consumption or export. This results in over 7500 tonnes of CSS produced each year which is typically disposed of as solid waste. Silverskin contains lignocellulose and can be used as a substitute for other raw materials to produce paper pulp. Both Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) were performed to compare the impact and cost of CSS paper production to conventional paper production using only virgin pulp. It was shown that the addition of CSS reduces the environmental impact of paper production by 10% and greenhouse gas (GHG) emissions by 13% compared to conventional production with no cost increase (0.01% reduction with addition of CSS) for the producer. The results of this case study show that the utilization of CSS for paper production at the national level in Italy represents a suitable example of circular economy (CE).

https://doi.org/10.3390/su13169069 Academic Editors:

Keywords: circular economy; life cycle assessment; life cycle costing; agri-industry residues; energy savings; waste valorization

Ioannis Arzoumanidis and Alberto Simboli Received: 22 July 2021 Accepted: 11 August 2021 Published: 13 August 2021

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁliations.

1. Introduction In 2018, the EU’s primary energy consumption accounted for approximately 1600 million tons of oil equivalent per year (Mtoe/y), of which a major contribution is provided by heating and cooling applications (around 800 Mtoe/y, which also includes industrial heat), followed by transport and electricity—which account for nearly 520 Mtoe/y and 280 Mtoe/y, respectively [1–4]. By 2030, the EU intends to further lower domestic greenhouse gas (GHG) emissions by 55% relative to 1990 levels. Moreover, EU countries have declared the goal of being the first climate neutral continent by 2050 [5,6]. The fulfilment of the Paris COP21 agreement is going to require equal, if not more, reduction of GHG emissions [6]. Circular economy (CE) plays a crucial role in this scenario. Circular economy intends to recover and valorize wastes and residues (from here on referred to as byproducts), adding value to these materials which can be included back into supply chains and minimizing the waste creation along the production pathways [7]. Moreover, the CE concept is gaining attention among researchers and institutions since it has potential to increase the sustainability of production and consumption systems [8]. According to the European Parliament, CE could increase the gross domestic product by 0.5% and create about 700,000 new jobs in the EU by 2030 [7]. By tapping into previously unexploited pools of byproducts, a new, valuable resource is available.

Sustainability 2021, 13, 9069. https://doi.org/10.3390/su13169069

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A study published by the EU in 2010 revealed that nearly 90 million tons of food byproducts are expelled from the food manufacturing industry every year [9]. Food industry byproducts could be utilized as raw material for multiple purposes. For example, large amounts of lignocellulosic material from food processing can be converted into ethanol [10] or biogas [11]. Food byproducts are also a potential reservoir for high valueadded chemicals [12,13], including lipids, nutraceuticals, other bioactive compounds, bioplastics, etc. A recent report demonstrates that production of bulk chemicals from biomass waste is 3.5 times more profitable than converting it into biofuel [14]. Coffee is one of the world’s most popular beverages, amounting to about ten million tonnes of roasted coffee consumed annually worldwide (2018/2019). In 2015, Italy was the third-largest international green coffee importer, after the USA and Germany. Coffee is imported into Italy for roasting which, together with brewing, is the industrial process responsible for the final flavor and aroma of coffee. Different byproducts are produced along the whole coffee life cycle [15]. In the past 10 years, spent coffee grounds have received significant attention, especially as an alternative bioenergy resource [16]. Oil suitable for biodiesel production can be extracted from spent coffee grounds or these residues can be transformed into bricks and pellets which could be used in domestic wood burners and multi-fuel stoves [17]. The coffee roasting process also generates a biowaste called coffee silverskin (CSS). Coffee silverskin is a very thin, papery material accounting for about 1.5% of the total mass of unroasted coffee. In Italy, approximately 7500 tonnes of CSS are produced each year due to the large coffee roasting industry [15,16]. Currently CSS is largely unexploited and, to the best of our knowledge, no major valorization of CSS is on the market yet. FAVINI srl [18], a company producing paper since 1736, developed a method called “CRUSH” which involves the use of byproducts and residues of agri-food transformations to produce paper. The vegetable residues (peels, shells, or pits) are dried at controlled temperature and milled to obtain a flour that is micronized and added to paper pulp. The amount of these flours can reach nearly 15% by weight, with significant savings of virgin cellulose [19]. Within the multidisciplinary project “CirCo-Multi valorization of silverskin, a residue of the coffee roasting industry” (funded by The Cariplo Foundation and Innovhub Stazioni Sperimentali per l’Industria S.r.l. [20]), the possibility to use these industrial coffee byproducts as a raw material in other industrial processes, embracing the CE concept, is examined. Silverskin is mainly formed by cellulose together with other value-added chemicals (i.e., polyphenols, fat, and waxes) that are extremely interesting for its valorization [21]. Due to the high content in cellulose and to the significance of reducing the import of virgin cellulose in Italy, the use of CSS in paper manufacturing was envisaged [15]. Samples of graphic paper containing 15% of micronized CSS have been prepared in the framework of the CirCo project and its quality was found to be comparable with that of conventionally prepared paper. However, besides the verification of the technical feasibility of using CSS as a raw material for paper production, it is fundamental to assess the sustainability of this new circular system since prolonging the lifetime of a material (i.e., byproduct) does not automatically confer sustainability. When modifications to the current industrial system occur due to the inclusion of byproducts, it is fundamental to verify their potential in reducing resource and energy consumption, greenhouse gas (GHG) emissions, and other environmental, economic, and social burdens along the whole life-cycle chain. Life cycle assessment (LCA) and life cycle costing (LCC) analyses are powerful tools for considering the environmental and economic sustainability of a particular good. Life cycle assessment is an internationally standardized (ISO 14040/2006 [22]; ISO 14044/2006 [23]) methodology that allows a quantitative assessment of the environmental performance of a product, process, or system along their whole life cycle. Based on the LCA concept, the LCC method evaluates the costs occurring along the whole chain, analyzing the economic side of sustainability [7].

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The goal of this study is to verify that use of CSS as a raw material for paper production decreases energy demand and environmental costs and increases economic benefits for the Italian graphic paper sector. The results of this work provide useful insights to entrepreneurs and to policy makers, identifying environmental and economic trade-offs which could occur along the system’s life cycle. Based on the investigation performed in the CirCo activities report [24] and Boschiero & Pezzutto, 2019 [8], which are characterized by a consistent input from the CirCo project form [15], an elaborated analysis has been carried out. We explain, in detail, the context of the investigation, provide an interpretation of the main findings, and discuss its implications. The following section, Section 2, includes the materials and methodology that supported the study. Section 3 specifies the primary outcomes in findings and figures. Section 4 critically evaluates the top results, and Section 5 indicates the conclusions with potential future implications and recommendations. 2. Materials and Methods 2.1. Life Cycle Assessment (LCA) This study aims to evaluate the environmental performance of CSS paper production compared to conventional paper production—where the raw materials include only virgin pulp and recycled paper. The CirCo project assessed graphic paper on the national (Italian) market. As a result, national average values have been used. For instances when using these values was not possible, data from the FAVINI srl paper mill (CirCo project partner) was assumed to be representative of national averages. It is assumed that the paper mill is located in northern Italy (Milan) according to the average national distribution of these companies as reported by ASSOCARTA, 2017 [25]. The functional unit that is considered is 1 kg of graphic paper. The LCA encompasses “cradle” to “grave” attributes. Both conventional paper production and silverskin paper production systems were modelled. Figures 1 and 2 provide a detailed scheme of these two systems.

Figure 1. Scheme of conventional paper production system. The system boundary is represented by the dashed line and transport phases are represented by grey arrows.

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Figure 2. Scheme of the paper production system using coffee silverskin as raw material. The system boundary for silverskin as a byproduct of coffee roasting is represented by the dotted line and transport phases are represented by the grey arrows.

2.1.1. Conventional Paper Production Conventional graphic paper is principally composed of wood pulp, recycled paper pulp, chemicals, and additives. According to FAVINI srl, pulp contributes approximately 64.6% of the weight of a sheet of graphic paper. In this case, three wood pulps are used: Eucalyptus virgin pulp from Brazil, Softwood virgin pulp from Scandinavian countries (the model assumes Sweden), and Hardwood virgin pulp from Slovakia. Recycled paper pulp was assumed to have been produced within national borders. Please see Table 1: Table 1. Pulp composition for conventional and silverskin papers. Pulp Typology

Origin Country

Conventional Paper

Silverskin Paper

Hardwood Eucalyptus Softwood Recycled-paper pulp (Italy) Silverskin Total

Slovakia Brazil Sweden

10.2% 11.86% 10.2%

8.11% 8.11% 9.46%

Italy

67.74%

54.05%

Italy

100%

20.27% 100%

The percentages of pulp typology for conventional graphic paper that were used in this study reﬂects the Italian national paper production, where softwood (58%) is utilized more than hardwood (42%) [25]. The process can be described in four key parts: Wood cultivation, pulp production, paper production, and use/recycling phase.

• • • • •

Wood production involves the processes required in the cultivation of the wood species considered in this study as well as the transportation to the pulp producer. Pulp production phase involves tree cultivation processes, wood management and handling, wood transportation to the pulp-mill, and, ﬁnally, the bleached pulp production and the transportation of these materials to the paper mill. Paper production phase involves the process of creating graphic paper. Paper production was assumed to take place in northern Italy (Milan), representing the Italian paper industry distribution. Use/recycling phase involves the transportation to the end-user to a waste-collection point as well as the recycling process. All transportation that occurs along the entire cycle has been grouped together to assess their impact.

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Each stage also includes additional processes in addition to these main processes, such as raw materials production, energy production, etc. 2.1.2. Silverskin Paper Production In the case of CSS paper production, the production of the CSS itself was also included in the system. Coffee Silverskin is a waste residue and can therefore be considered either a byproduct or a co-product when performing a LCA [26]. How it is considered influences the system boundaries and the allocation procedures. In this case study, CSS was assumed to be a byproduct and therefore no mass allocation during coffee production was performed. The system boundary starts with the transportation of CSS to the micronization facility. 2.1.3. Life Cycle Inventory (LCI) Primary and secondary data were used. The study retrieved most of the data for the main processes from Ecoinvent v3.0 [27], including the production of pulps, paper, alkyl ketene dimer, brighteners, potato starch, pesticide, glyphosate, coffee cultivation, eucalyptus plantation, paper recycling, etc. This data was then inserted into the GaBi database [28]. However, several background-based processes and flows that are available in Ecoinvent v3.0 are not present in the database (e.g., sulphur dioxide production, sodium sulphate production, etc.), and, as a result, were not included. When possible, proxy processes were used. All the data on national quantities and fluxes of materials for paper making as well as all the data related to the country of origin and the main pulp and paper producers at both the national and international levels were provided by FAVINI srl and ASSOCARTA [25]. Data on the technology typology that was used to produce virgin pulp were taken from a technical report published by the Energy Technology Systems Analysis Programme [29] and by Silva et al., 2015 [30]. According to the results, the sulphate pulp (or kraft pulp) was the most frequently used technology. Data on the production process for pulps were obtained from Ecoinvent v3.0. It was assumed that the whole wood produced was used exclusively for paper production. Data on the materials and energy used for papermaking, as well as the origin of the material used for papermaking, are provided by FAVINI srl, as were data. All data for the transportation processes and background processes (energy, material, chemicals production, etc.) were obtained from Ecoinvent and GaBi databases. Data on coffee cultivation was obtained from literature [16,31,32], while the process of cultivation is provided by Ecoinvent v3.0. Data needed to estimate the energy and materials consumptions of the roasting process was unavailable. Only energy consumption data was available for micronization. These have been indicated by FAVINI srl. In the following sections, the inventory of each main process is explained in detail. 2.1.3.1. Eucalyptus Plantation and Eucalyptus Pulp Production Dataset inventories of the production of Eucalyptus plantation were obtained from two dedicated LCA studies: Silva et al., 2013 [33] and Silva et al., 2015 [30]. Data refers to 1 kg of logs oven dry with a density of 474 kg/m3 . The process that was assessed in the studies included seedling cultivation, soil preparation, seedling transplanting, forest management, harvesting, and transport. Since the majority of pulp production companies are located close to the Eucalyptus cultivation sites (mostly in São Paulo and Bahia) [34], a transport distance from the Eucalyptus plantation to the pulp mill infrastructure of 200 km carried out by truck was assumed (Euro 3, 34–40 t). The process of Eucalyptus virgin pulp production was taken from Ecoinvent v3.0 (process name: “Sulphate pulp, from Eucalyptus, unbleached, at plant”).

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Transportation of the Eucalyptus pulp from Brazil to Italy was performed by a container ship (about 10,000 km) followed by road transport for an average of 300 km by truck (Euro 3, 34–40 t). 2.1.3.2. Softwood Plantation and Softwood Pulp Production Because Sweden is both the leading virgin pulp producer in the EU and the biggest European exporter of pulp for Italy [25], this study assumed that all the virgin pulp originated in Sweden. The softwood timber production process was obtained from the GaBi database. It is assumed that the required transportation of the harvested wood from the forest field to the pulp company is 100 km by truck (Euro 3, 34–40 t). The pulp production process was modelled according to the Ecoinvent v3.0 process “Sulphate pulp, Scandinavian wood, elemental chlorine free (ECF) bleached, at plant”. The transportation of Swedish virgin pulp to Italy was carried out about 1000 km by ship from Stockholm to Rostock (DE), and approximately 1300 km by truck from Rostock to Milan. 2.1.3.3. Hardwood Plantation and Hardwood Pulp Production According to FAVINI srl, hardwood fibers are critical in the production of graphic paper. The process of producing hardwood timber was obtained from the GaBi database. It was assumed that the transportation of the harvested wood from the forest field to the pulp company is around 100 km by big truck (Euro 3, 34–40 t). The process for producing pulp was modelled in accordance with the Ecoinvent v3.0 process “Sulphate pulp, Scandinavian wood, ECF bleached, at plant”. Transportation of hardwood virgin pulp to Italy is performed by truck (from the middle of Slovakia to Milan, which is about 1000 km). 2.1.3.4. Paper Recycling and Pulp from Wasted Paper The process of pulp production for this material was obtained from Ecoinvent v3.0 “Sulphate pulp, ECF bleached”. It was assumed that 75% of the used paper is collected. During the sorting process, 2.5% of the harvested paper could not proceed with pulping (because of metal parts, plastic parts, etc.). This data was obtained from Ecoinvent v3.0. According to the European Declaration of Paper Recycling [35], the final recycling rate is 72.5%. It is assumed that there is a system of urban/industrial collection carried out with small trucks (up to 7.5 t). The average distance is 50 km. The wasted paper from the storing urban site is then transported to a dedicated sorting and recycling site with a truck of 26–28 t for about 100 km where it is sorted and transported to the pulp industry (which we hypothesize is located in northern Italy). As reported in ASSOCARTA 2017, Italy imports only around 7% of the recycled paper, the majority of which originates in Germany (about 21%). It was decided to model only the national recycling system and to exclude imports. Transportation of recycled-paper-pulp is carried out by truck (Euro 3, 34–40 t) for around 500 km. 2.1.3.5. Coffee Silverskin Production It was assumed that the roasted coffee travels with a truck for approximately 375 km on average from the roasting plant to the micronization site (from Trieste to Cuneo: about 600 km, Genova-Cuneo: around 150 km; average: 375 km). Only the energy consumption was considered for the micronization process: 450 kWh per 1 t of silverskin [36]. Furthermore, the following assumptions were made in creating the LCA:

• •

The micronized CSS travels for an average of about 350 km to reach the ﬁnal papercompany—mean Italian distance from mills able to micronize silverskin to paper producing companies [25,37]. Silverskin replaces 15% of the virgin pulp used in the “conventional paper production” system [18].

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• • • •

Electricity used in this step is the average Italian mix [38]. To obtain 1 kg of green coffee, 2 kg of dried red berries are used [39]. Silverskin is 1.5% of the roasted beans [16]. Mass allocation between coffee and CSS is applied when CSS is considered as a co-product.

2.1.3.6. Paper Making Data on the materials and quantities that are used to produce the graphic paper are reported in Table 2 below. Table 2. Data on materials used to produce the graphic paper. Data are given per functional unit. INPUT Materials

Unit

Amount

Pulp mix

0.646

Limestone

0.202

Alkyl ketene dimers sizer

0.004

Potato starch

0.040

Brighteners

0.001

Water

23.000

Chemicals

0.037

Electricity

1.477

Natural gas

13.386

Once the paper is produced, transportation to the consumers was estimated to be approximately 200 km, carried out with a Euro 3 (26–28 t) truck. Paper use was not included in the study due to high variability that results from consumer habits. However, the required effort of the consumer for the transport to the waste-collection site was taken into consideration. 2.1.3.7. Life Cycle Impact Assessment The 100-year time horizon global warming potential (GWP) methodology from the IPCC Fifth Assessment Report 2014 (AR5) [40] was used to calculate the global warming potential (GWP). Following the IPCC (2006) guidelines [41], biogenic carbon was not included in this study. Results are reported in kg of CO2 eq (kg CO2 eq) per functional unit (FU). The primary energy demand (PED) methodology was selected to evaluate the energy consumption of the systems. The data refers to the net energy demand (expressed in MJ), subdivided by renewable and non-renewable energy. The life cycle impact assessment method ReCiPe [42] was used to calculate several other environmental impacts of the two paper types. ReCiPe provides a wide range of impacts, covering the whole environment-sphere (from atmosphere, to soil, to human toxicity). In total we analyzed 20 mid-point impact categories (Table 3). The impacts of land occupation and transformation were not included in the assessment. 2.2. Life Cycle Costing (LCC) The LCC methodology is congruent with the methodology of the LCA and follows the methodology described by Swarr et al. (2011) [43] and Hunkeler et al. (2008) [44]. Even though LCC is a well-established concept, it has never been explicitly developed in a common and standardized methodology [44]. Within the given assessment, we performed a so-called environmental LCC as described by Hunkler et al. (2008), where the ﬁnancial costs are assessed per each life cycle step together with the costs associated to the environmental impacts.

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Table 3. Mid-point impact categories assessed. Environmental Impact Name

Acronym

Unit

Global Warming Potential Primary energy demand PED non renewables PED renewable Fine Particulate Matter Formation Fossil depletion Freshwater Consumption Freshwater ecotoxicity Freshwater Eutrophication Human toxicity, cancer Human toxicity, non-cancer Ionizing Radiation Marine ecotoxicity Marine Eutrophication Metal depletion Photochemical Ozone Formation, Ecosystems Photochemical Ozone Formation, Human Health Stratospheric Ozone Depletion Terrestrial Acidiﬁcation Terrestrial ecotoxicity

GWP PED PED nr PED r FPMF FD FC FE FEu HT c HT nc IR ME MEu MD POF, E POF, HH SOD TA TE

kg CO2 eq. MJ MJ MJ kg PM2.5 eq. kg oil eq. m3 kg 1.4 DB eq. kg P eq. kg 1.4-DB eq. kg 1.4-DB eq. Bq C-60 eq. to air kg 1.4-DB eq. kg N eq. kg Cu eq. kg NOx eq. kg NOx eq. kg CFC-11 eq. kg SO2 eq. kg 1.4-DB eq.

However, we also included the dimension of environmental impacts, monetizing the environmental impacts assessed in the LCA. We took the mean of values reported by Pizzol et al. (2015) [45] as monetization values. The overall structure of the LCC is performed by following the indication given by Amerighi (2016) [46]. 2.2.1. Goal and Scope Deﬁnition The goal of this study is to estimate the life cycle cost for producing 1 kg of graphic paper using CSS instead of conventional wood-pulps. In addition, a comparison with conventional graphic paper will be carried out, as well. 2.2.2. Calculation of Life Cycle Costs The calculation of life cycle costs is based on the LCI of the previous LCA. As a result, both the FU and the system boundaries are the same. The materials within the inventory were multiplied by the speciﬁc prices, including research and development (R&D) as well as labor costs. All costs that occur before the procurement of raw materials (e.g., extraction costs, production costs, transport costs, etc.) have been included/aggregated in the price of raw material itself. These data were retrieved from the paper producing company FAVINI srl. The cost of CSS is 0.00 € as it is given away for free. Data regarding operational costs, such as those regarding electricity and natural gas, were taken from EUROSTAT [47]. Moreover, data about the wastewater treatment cost were taken from [48]. Data are presented in Tables 4 and 5. Due to the lack of involvement of long-term intervals, discounting is not applied. We also included the environmental costs that resulted from each of the two systems in the assessment. To do this, the costs that were derived from the environmental impacts assessed in the previous LCA were internalized. The mean of values reported by Pizzol et al., 2005 [45] (see Table 6) were calculated and used for further monetary calculations.

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Table 4. Costs associated with conventional paper production life cycle. Phase

Cost’s Voice

Quantity

Unit

Unit Cost

Unit

Costs (€)

Sources

0.5

hour

€/hour

FAVINI srl

Research and Development Work (researcher/engineer) Subtotal

Raw material acquisition kg

0.20 €

€/kg

0.007 €

FAVINI srl

0.001

0.75 €

€/kg

0.001 €

FAVINI srl

0.202

0.06 €

€/kg

0.012 €

FAVINI srl

AKD sizer

0.00434

0.60 €

€/kg

0.003 €

FAVINI srl

Waste-paper pulp (Italy)

0.349206

0.65 €

€/kg

0.227 €

FAVINI srl

Eucalyptus pulp (Brazil)

0.09599

0.63 €

€/kg

0.060 €

FAVINI srl

Softwood pulp (Sweden)

0.104775

0.76 €

€/kg

0.080 €

[24]

Hard-wood pulp (Slovakia)

0.09599

0.60 €

€/kg

0.058 €

FAVINI srl

Potato starch

0.0397

0.42 €

€/kg

0.017 €

FAVINI srl

Pigment

0.0008

2.50 €

€/kg

0.002 €

FAVINI srl

Chemicals, inorganic

0.0372

Silica ﬂour Limestone

0.466 €

Subtotal Production Electricity

0.4104

kWh

0.1449

€/kWh

0.059 €

[49]

Natural gas, consumer price, Italy

3.72

kWh

0.0253

€/kWh

0.094 €

[50]

Water

1.73

€/mc = t

0.040 €

[48]

Work

hour

€/hour

25 25.193 €

Subtotal Depreciation and taxes Wastewater treatment

21.597

€/kg

86.388 €

Subtotal

86.388 €

Subtotal

[24]

Use Recycling Collection

41.2

€/t

0.041 €

[24]

Sorting

0.725

€/t

0.025 €

[51]

Transport to re-processor

0.707

22.9

€/t

0.016 €

[51]

Revenue for baled paper

0.349206

−21.6

€/t

−0.008 €

[51]

Subtotal

0.075 €

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Table 5. Costs associated with Silverskin paper production life cycle. Phase

Cost’s Voice

Quantity

Unit

Unit Cost

Unit

Costs (€)

Sources

0.8

hour

€/hour

FAVINI srl

Research and Development Work (researcher/ engineer) Subtotal

Raw material acquisition kg

0.20 €

€/kg

0.007 €

FAVINI srl

0.001

0.75 €

€/kg

0.001 €

FAVINI srl

0.202

0.06 €

€/kg

0.012 €

FAVINI srl

AKD sizer

0.00434

0.60 €

€/kg

0.003 €

FAVINI srl

Wastepaper pulp (Italy)

0.349141

0.65 €

€/kg

0.227 €

FAVINI srl

Eucalyptus pulp (Brazil)

0.052387

0.63 €

€/kg

0.033 €

FAVINI srl

Softwood pulp (Sweden)

0.061108

0.76 €

€/kg

0.046 €

Index Mundi

Hardwood pulp (Slovakia)

0.052387

0.60 €

€/kg

0.031 €

FAVINI srl

Silverskin

0.130936

0.00 €

€/kg

0.000 €

Potato starch

0.0397

0.42 €

€/kg

0.017 €

FAVINI srl

Pigment

0.0008

2.50 €

€/kg

0.002 €

FAVINI srl

Chemicals, inorganic

0.0372

Silica ﬂour Limestone

0.380 €

Subtotal Production Electricity

0.4104

kWh

0.1449

€/kWh

0.059 €

[49]

Natural gas, consumer price, Italy

3.72

kWh

0.0253

€/kWh

0.094 €

[50]

Water

1.73

€/mc = t

0.040 €

[48]

Work

hour

€/hour

25 25.193 €

Subtotal Depreciation and taxes Wastewater treatment

21.597

€/kg

86.388 €

[24]

86.388 €

Subtotal Silverskin supply Micronization

0.130936

800

€/t

0.10 €

FAVINI srl

Transport diesel consumption

0.002304

1.488.03

€/t

0.0034 €

[52] (average 2018)

Subtotal

0.11 €

Subtotal

Use Recycling

Collection

41.2

€/t

0.041 €

[51]

Sorting

0.725

€/t

0.025 €

[51]

Transport to re-processor

0.707

22.9

€/t

0.016 €

[51]

Revenue for baled paper

0.349206

−21.6

€/t

−0.008 €

[51]

Subtotal

0.075 €

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Table 6. Monetary values [45]. €/unit

Monetary Values of Environmental Impacts

Max.

Min.

Mean

Global warming [kgCO2 eq]

0.23

0.05

0.108

Ozone depletion [kgCFC11 eq]

139.56

89.853

Acidiﬁcation [kgSO2 eq]

6.4

0.15

3.226

Eutrophication [kgPO4 eq]

25.35

1.2

8.384

Photochemical oxidation [kgC2 H4 eq]

55.82

0.56

15.606

Abiotic Resources [MJ]

0.02

0.00047

0.008

Human-toxicity [kg1.4DBeq]

1.4

0.00154

0.524

Unfortunately, the impacts that we considered within the LCA have not all been monetized. Thus, in the LCC we included only the impacts for which we found a value (i.e., global warming, ozone depletion, acidiﬁcation, and human toxicity). 3. Results 3.1. LCA Results Conventional Paper The values of the impacts assessed for conventional paper production processes are shown in Table 7 and Figure 3. Table 7. Impacts of the conventional paper production expressed per functional unit, divided by main processes. System’s Phases Environmental Impacts

Wood Cultivation

Pulp Production

Paper Production

Transport

Recycling

Total

GWP [kg CO2 eq.]

3.46 × 10−1

2.92 × 10−1

4.58 × 10−1

5.28 × 10−2

1.67 × 10−2

1.17 × 10

PED [MJ]

5.28 × 10

4.38 × 10

2.12 × 10+1

7.31 × 10−1

2.89 × 10−1

3.19 × 10+1

PED nr [MJ]

3.33 × 10

3.72 × 10

1.88 × 10+1

7.01 × 10−1

2.32 × 10−1

2.68 × 10−1

PED r [MJ]

1.94 × 10

6.59 × 10−1

2.38 × 10

2.96 × 10−2

5.73 × 10−2

5.07 × 10

FPMF [kg PM2.5 eq.]

5.29 × 10−4

1.58 × 10−3

2.53 × 10−4

1.49 × 10−4

2.55 × 10−5

2.54 × 10−3

FD [kg oil eq.]

7.87 × 10−2

8.70 × 10−2

4.53 × 10−1

1.64 × 10−2

5.43 × 10−3

6.41 × 10−1

FC [m3 ]

1.29 × 10−3

4.97 × 10−2

2.57 × 10−2

5.45 × 10−5

1.20 × 10−3

7.79 × 10−1

FE [kg 1.4 DB eq.]

1.10 × 10−4

6.63 × 10−5

6.47 × 10−5

9.8 × 10−6

1.76 × 10−6

2.53 × 10−4

FEu [kg P eq.]

7.20 × 10−6

1.68 × 10−5

1.18 × 10−5

1.94 × 10−7

4.24 × 10−8

3.61 × 10−5

HT. c [kg 1.4-DB eq.]

2.32 × 10−4

2.47 × 10−4

3.09 × 10−4

1.40 × 10−5

2.85 × 10−3

3.65 × 10−3

HT. nc [kg 1.4-DB eq.]

4.06 × 10−2

2.65 × 10−2

−4.53 × 10−4

4.6 × 10−3

3.44 × 10−4

7.17 × 10−2

IR [Bq C-60 eq. to air]

3.9 × 10−4

3.63 × 10−3

5.43 × 10−3

3.02 × 10−5

2.64 × 10−4

9.75 × 10−3

ME [kg 1.4-DB eq.]

2.97 × 10−4

5.62 × 10−4

1.47 × 10−4

2.82 × 10−5

7.89 × 10−6

1.04 × 10−3

MEu [kg N eq.]

5.99 × 10−5

1.53 × 10−4

1.39 × 10−4

1.04 × 10−6

3.70 × 10−7

3.53 × 10−4

MD [kg Cu eq.]

1.39 × 10−3

3.18 × 10−3

4.93 × 10−3

2.37 × 10−5

5.78 × 10−1

1.01 × 10−2

POF. E [kg NOx eq.]

3.12 × 10−1

1.28 × 10

1.18 × 10

4.27 × 10−3

7.44 × 10−1

3.52 × 10

2.92 ×

10−3

4.62 ×

10−1

2.18 × 10

1.33 ×

10−8

5.32 ×

10−9

2.11 × 10−6

POF. HH [kg NOx eq.] SOD [kg CFC-11 eq.]

1.94 ×

10−1

1.42 ×

10−6

7.92 ×

10−1

1.22 ×

10−7

7.32 ×

10−1

5.55 ×

10−7

TA [kg SO2 eq.]

1.46 × 10−3

5.32 × 10−3

7.88 × 10−4

4.57 × 10−4

8.46 × 10−5

8.10 × 10−3

TE [kg 1.4-DB eq.]

1.92 × 10−1

6.99 × 10−1

8.94 × 10−2

2.16 × 10−3

6.82 × 10−3

9.89 × 10−1

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Figure 3. Comparison of the environmental impacts of the two investigated productions of paper—conventional (in blue) and with the addition of silverskin (in orange). Please note that the abbreviations present in this ﬁgure, are explained within Table 3 above.

In the majority of the impact categories, the most impactful phases are paper production and pulp production. Concerning carcinogenic human toxicity, the recycling phase is the most signiﬁcant contributor, especially the incineration of wasted paper (the share that cannot be recycled). Please see Table 8: The comparison displayed in Figure 3 shows that the conventional paper production causes a higher environmental impact for each impact category. When performing the comparison at endpoint single-score level following the ReCiPe Hierarchy method, the systems could be ordered as follows: Conventional paper (0.156 point-Pt) > CSS paper (0.142 Pt). Based on these endpoint scores, there is about 10% environmental impact reduction of the CSS paper generation methodology related to the conventional one. Please see Figure 3: There is a 13% GHG emission reduction concerning the silverskin paper production compared to the conventional one. Main factors of inﬂuence are given by (see Figure 4) a reduction of CO2 emissions in the cultivation of wood and regarding pulp production. 3.2. LCC Results The LCC results show that the difference between the two paper typologies is very small (−0.01% using the CSS production method). The CSS paper indicates marginally higher acquisition costs for raw material (+8%). However, less costs associated with environmental impacts are generated (about −16%). Table 9 summarizes the indications mentioned above:

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Table 8. Impacts of silverskin paper production expressed per functional unit, divided by main processes. System’s Phases Environmental Impacts GWP [kg CO2 eq.]

Wood Cultivation

Silver-Skin Supply

Pulp Production

Paper Production

Transport

Recycling

Total

2.95 × 10−1

2.49 × 10−2

2.34 × 10−1

4.58 × 10−1

6.50 × 10−2

1.67 × 10−2

1.09 × 10

10−1

3.12 × 10+1

10−1

3.47 × 10

2.12 ×

PED [MJ]

4.67 × 10

6.33 ×

PED nr [MJ]

2.88 × 10

3.55 × 10−1

2.95 × 10

1.88 × 10+1

8.74 × 10−1

2.32 × 10−1

2.61 × 10+1

PED r [MJ]

1.79 × 10

2.78 × 10−1

5.19 × 10−1

2.38 × 10

4.07 × 10−2

5.73 × 10−2

5.07 × 10

10−5

10−3

10−4

10−5

2.16 × 10−3

FPMF [kg PM2.5 eq.]

4.48 ×

10−4

1.00 ×

1.28 ×

2.53 ×

10+1

10−4

9.15 ×

1.46 ×

2.89 ×

2.55 ×

FD [kg oil eq.]

6.80 × 10−2

8.31 × 10−3

6.91 × 10−2

4.53 × 10−1

2.05 × 10−2

5.43 × 10−3

6.25 × 10−1

FC [m3]

1.11 × 10−3

2.93 × 10−4

3.95 × 10−2

2.57 × 10−2

7.50 × 10−5

1.20 × 10−3

6.79 × 10−2

10−5

10−6

10−5

10−6

2.32 × 10−4

FE [kg 1.4 DB eq.]

9.80 ×

1.86 ×

5.28 ×

6.47 ×

1.24 ×

1.76 ×

FEu [kg P eq.]

5.12 × 10−6

1.40 × 10−7

1.34 × 10−5

1.18 × 10−5

2.67 × 10−7

4.24 × 10−8

3.08 × 10−5

HT. c [kg 1.4-DB eq.]

2.05 × 10−4

6.06 × 10−6

1.97 × 10−4

3.09 × 10−4

1.76 × 10−5

2.85 × 10−3

3.58 × 10−3

HT. nc [kg 1.4-DB eq.]

3.63 ×

10−2

10−3

10−4

6.27 × 10−2

IR [Bq C-60 eq. to air]

3.45 × 10−4

4.96 × 10−4

2.80 × 10−3

5.43 × 10−3

3.92 × 10−5

2.64 × 10−4

9.38 × 10−3

ME [kg 1.4-DB eq.]

2.65 × 10−4

7.17 × 10−6

4.49 × 10−4

1.47 × 10−4

3.52 × 10−5

7.89 × 10−6

9.11 × 10−4

10−5

10−7

10−4

10−6

10−7

3.18 × 10−4

−8.61 ×

2.13 ×

−4.53 ×

6.00 ×

1.05 × 10−3

5.26 × 10−5

2.58 × 10−3

4.93 × 10−3

3.25 × 10−5

5.78 × 10−4

9.23 × 10−3

POF. E [kg NOx eq.]

2.69 × 10−1

5.49 × 10−2

1.02 × 10

1.18 × 10

5.34 × 10−3

7.44 × 10−1

3.27 × 10

1.68 ×

10−1

3.41 ×

10−2

3.62 ×

10−3

4.62 ×

10−1

2.03 × 10

1.19 ×

10−6

9.08 ×

10−9

1.62 ×

10−8

5.32 ×

10−9

1.87 × 10−6

TA [kg SO2 eq.] TE [kg 1.4-DB eq.]

6.31 × 9.77 ×

10−8

7.32 ×

10−1

5.55 ×

10−7

1.43 ×

3.44 ×

MD [kg Cu eq.]

10−1

1.39 ×

10−4

5.37 ×

SOD [kg CFC-11 eq.]

1.22 ×

10−2

MEu [kg N eq.]

POF. HH [kg NOx eq.]

8.98 ×

10−4

3.70 ×

1.23 × 10−3

3.25 × 10−5

4.30 × 10−3

7.88 × 10−4

4.42 × 10−4

8.46 × 10−5

6.88 × 10−3

10−1

10−3

10−1

10−2

10−3

8.40 × 10−1

1.72 ×

9.40 ×

5.59 ×

8.94 ×

2.69 ×

6.82 ×

Figure 4. Comparison of the greenhouse gas emissions of the two investigated productions of paper—conventional at one hand (in blue) and with silverskin at other hand (in orange).

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Table 9. Paper production costs of the two analyzed systems (conventional and with the use of silverskin). Data refers to euro (€) or million euro (M€). Research and Development

Raw Material Acquisition

Production

End of Life

Depreciation and Taxes

Environmental Impacts

Total

Conventional paper

0.0 €

16.296 M€

18.368 M€

4.339 M€

4983 M€

10.655 M€

5.034 M€

CSS paper

9200.0 €

17.528 M€

18.368 M€

4.339 M€

4983 M€

8.928 M€

5.033 M€

Δ (CSS-conventional)

100%

−16%

−0.01%

LCC

4. Discussion Comparing the results with other studies is difficult for numerous reasons. A specific system is analyzed in each study, which may sometimes allow for reasonable comparisons when assumptions are made. Furthermore, various distinct impact assessment methods are selected, and separate impact categories are analyzed, making any comparisons even more problematic. The figure regarding GWP that was obtained in our study is in line with the figure reported in two separate carbon-footprints carried out for FAVINI srl regarding paper made with other agricultural residues. Our results for conventional paper are in line with the figures reported in Silva et al., 2015 [30]. The LCA results show that there is an advantage in including coffee silverskin in paper production compared to using virgin pulp alone. There is approximately 10% environmental impact reduction through the incorporation of CSS in paper production method relative to using virgin pulp alone. Moreover, we registered a 13% reduction in GHG emissions concerning the CSS paper production method compared to the conventional method. This result should not be taken for granted. The use of agri-food byproducts as secondary raw materials is a topic of relevant interest in the Bio-economy scenario that is strongly encouraged by the EU. However, some initiatives have turned out to be less sustainable than conventional disposal, such as landfilling, after a careful LCA analysis. This was the case with the use of spent coffee grounds to produce biodiesel in the UK according to one recent study [53]. In addition to the environmental benefits conferred by incorporating CSS into paper production, the LCC analysis indicates that the difference in cost of production is competitive and marginally lower for CSS paper versus conventional paper. The LCC results show that the divergence between the two paper production methods is quite small: we determined a 0.01% reduction using the CSS production method. Data acquisition required a significant effort due to the unique material under study. There are data gaps in the scientific literature, especially on the topic of coffee processing and cultivation. These data, along with data regarding much of the paper production process, is only available through the private sector, making robust LCA and LCC results difficult to obtain. While the cooperation of FAVINI srl made good estimates of their processes possible, the conventional processes required many assumptions as far as transport distances: energy consumption for certain processes and sources for raw material. As with all LCA and LCC analyses, several assumptions were needed. One of the main considerations affecting the outcome of the model is how to consider the CSS itself. Silverskin is a residue and can thus be considered as either a waste or as a co-product when performing an LCA. If CSS is considered as a waste, then the system boundary should begin with the waste itself and a production system cut-off should be applied. Alternatively, if CSS is considered as a co-product, then the system boundary should include every necessary process required to attain that co-product (i.e., coffee cultivation, handling, transport, roasting, etc.). While both scenarios were explored, the main results presented represent the first scenario where CSS is considered as a waste product. The authors assumed this was appropriate given that the normal practice of disposal for CSS is disposal as solid waste. Of course, this leads to the entire CSS paper having a lower impact as the impacts from the coffee production itself are not considered. It should be mentioned,

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however, that even when CSS was considered as a co-product, the CSS paper production still outperformed conventional paper production. Considering the main results obtained, it is worth mentioning that the customers consumer behavior might favor the CSS option due to being more attractive because of environmental impact reasons. In recent years, there has been a substantial increase in demand for “green” products and, when marketed as such, consumers might be willing to accept a higher price point for a product with a lower environmental impact. In fact, one study showed that 37% of consumers are willing to pay up to 5% more for a more environmentally friendly product [54]. Further research concerning consumers’ willingness to pay with regards to CSS paper is recommended. Another point deserves to be mentioned. CSS has no market, at least in Italy, and this material is disposed of as a waste or given away for free to people interested in valorizing it. Following this work it could become a very attractive substitute for virgin cellulose in paper making, thus achieving a monetary value and adding proﬁt to the roasters. Of course this is where policy and regulation play a landmark role for the implementation of the circular economy and industrial symbiosis. 5. Conclusions To conclude the current work, the main ﬁndings are summarized as follows:

• • •

An about 10% environmental impact reduction can be achieved by substituting existing methods with the novel silverskin paper production method. We found approximately 13% reduction in greenhouse gas emissions when comparing the silverskin paper production method to the conventional method. The limited availability of data and information to carry out the given investigation required the study team to make several assumptions. Please refer to Section 2.1.3.5 (Coffee production) for more information concerning this issue.

Thus, the findings of the given case study demonstrate the feasibility in utilizing silverskin as a substitute to other raw materials to produce paper pulp at the Italian national level. These results also show the relevance of applying LCA analysis when designing circular economy and industrial symbiosis pathways. Author Contributions: Conceptualization. M.B., S.P., N.R. and E.O.; Data curation. M.B., S.P. and A.M.; Writing. E.O., S.P., M.B. and N.R.; Supervision. S.P., N.R. and A.M.; Validation. S.P., M.B., N.R. and A.M. All authors have read and agreed to the published version of the manuscript. Funding: This research was financed by the Cariplo Foundation and Innovhub-Stazioni Sperimentali per l’Industria S.r.l., Project 2017-0988. Acknowledgments: The authors would like to acknowledge FAVINI srl for providing essential data and information for the performed LCA and LCC analysis. Conflicts of Interest: The authors declare no conflict of interest.

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Numerical modeling for adjustment of the equivalent moduli of elasticity of OSB layers estimated from experimental flexural rigidity 1 2 2 2 JULIO SORIANO , JULIANO FIORELLI , WANLEY E. LOPES JUNIO , GUILHERME H.A. BARBIRATO , & 1 LEONARDO R. DELDOTTI .

Oriented strand board (OSB) panels are well-known for their many applications and as a complex multi-layer composite, which elastic properties are commonly obtained by testing the specimens for the longitudinal and transverse directions of the panel. This study aimed to establish a method to obtain the equivalent moduli of elasticity to each panel layer. For this purpose, OSB panels were manufactured from balsa wood waste and castor oil polyurethane resin. Based on the flexural rigidity for each panel direction and considering the geometric and elastic parameters, a system of the equations was established to obtain the equivalent moduli of elasticity of each layer. The method proposed was validated using the finite element method. The experimental results showed that the elastic-linear behaviour was quite accurate for up to approximately 60% of the ultimate stress, and thereafter the non-linearity was better fitted by a multi-linear model. The loaddeflection curves, both for the longitudinal and transverse directions, for the elastic phase were precisely represented with the equivalent moduli of elasticity. For non-linear segments, there was a strong dependence on the parameters adopted in the model. The results obtained in this study showed that the equivalent moduli of elasticity of layers of OSB panel can be obtained based on the results of bending test of specimens manufactured with the full thickness of the panel, providing properties for more detailed applications in the modeling with of this layered wood-based product. Contact information: 1 Department of Rural Constructions and Ambience, School of Agricultural Engineering, University of Campinas, Avenue Candido Rondon 501, Campinas, SP, 13083-875, Brazil. 2 Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering, University of S~ao Paulo, Avenue Duque de Caxias Norte 225, Pirassununga, SP, 13630-000, Brazil. journal of materials research and technology 2021; 14 : 1630 – 1643 https://doi.org/10.1016/j.jmrt.2021.07.048 Creative Commons Attribution 4.0 International License

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Article 7 – OSB Elastic Modulus

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Original Article

Numerical modeling for adjustment of the equivalent moduli of elasticity of OSB layers estimated from experimental ﬂexural rigidity Julio Soriano a,*, Juliano Fiorelli b, Wanley E. Lopes Junior b, Guilherme H.A. Barbirato b, Leonardo R. Deldotti a a

Department of Rural Constructions and Ambience, School of Agricultural Engineering, University of Campinas, Avenue Candido Rondon 501, Campinas, SP, 13083-875, Brazil b ~o Paulo, Department of Biosystems Engineering, Faculty of Animal Science and Food Engineering, University of Sa Avenue Duque de Caxias Norte 225, Pirassununga, SP, 13630-000, Brazil

article info

abstract

Article history:

Oriented strand board (OSB) panels are well-known for their many applications and as a

Received 14 March 2021

complex multi-layer composite, which elastic properties are commonly obtained by testing

Accepted 9 July 2021

the specimens for the longitudinal and transverse directions of the panel. This study aimed

Available online 20 July 2021

to establish a method to obtain the equivalent moduli of elasticity to each panel layer. For this purpose, OSB panels were manufactured from balsa wood waste and castor oil poly-

Keywords:

urethane resin. Based on the ﬂexural rigidity for each panel direction and considering the

Wood-based composites

geometric and elastic parameters, a system of the equations was established to obtain the

Finite element method

equivalent moduli of elasticity of each layer. The method proposed was validated using the

Multi-layer element

ﬁnite element method. The experimental results showed that the elastic-linear behavior

Deﬂections

was quite accurate for up to approximately 60% of the ultimate stress, and thereafter the

Bending stress

non-linearity was better ﬁtted by a multi-linear model. The load-deﬂection curves, both for the longitudinal and transverse directions, for the elastic phase were precisely represented with the equivalent moduli of elasticity. For non-linear segments, there was a strong dependence on the parameters adopted in the model. The results obtained in this study showed that the equivalent moduli of elasticity of layers of OSB panel can be obtained based on the results of bending test of specimens manufactured with the full thickness of the panel, providing properties for more detailed applications in the modeling with of this layered wood-based product. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

* Corresponding author. E-mail address: julio.soriano@feagri.unicamp.br (J. Soriano). https://doi.org/10.1016/j.jmrt.2021.07.048 2238-7854/Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Introduction

The development of wood-based products has been pointed to as essential to the sustainability of civil construction characterized using renewable resources, and such developments also impact the increase of agribusiness activities due to the cultivation of forests of fast-growing species. Simultaneously, solutions for the use of waste from the wood processing industry are provided, being regarded as a constant trend for new investments and ecological appreciation [1e3]. The mechanical behavior of products, such as glued-laminated timber, cross-laminated timber, plywood, and oriented strand board (OSB) is strongly influenced by the wood's nonhomogeneous properties, as well as the adhesive used in the composite production. In the case of the reconstituted wood panel, as particleboards and OSB panels, advances in the study concerning the properties and sustainability of this composite material have shown promise due to a possible composition including the use of waste wood and adhesives free of phenolic components, such as castor oil polyurethane resin [4,5]. OSB panels are commonly produced with three layers of thin wood strands, and the geometry, orientation of these elements, and thickness of each layer of strands reflect the stiffness and strength of the panel [6e9]. A wide range of applications for OSB is found in the furniture industry and in civil construction, such as wall panels, roofs, I-joist web, reinforcement of wood truss, and slabs composed of a lighttimber frame and OSB [10e13]. According to [14,15], OSB panels are manufactured under pressure and heat, with the outer layers generally arranged with longer strands aligned in the long dimension of the panel and, in the core layer the strands are arranged in the perpendicular direction. The densification effect is due to the pressing and high temperature applied in the panel manufacturing process, in which the OSB product is denser than the solid wood that originated the strands and the effectiveness of internal adhesion is greater for hardwoods than softwood species [16]. Additionally, the variation in the matrix density, both in the thickness and panel area, affects the properties of this composite, characterizing it as a material with complex behavior [17]. OSB is a composite treated as orthotropic [18,19], and, in general, the models for representing its elastic properties consider it in its full panel thickness, and not each layer with respective properties which can be quite different from one layer to another [20]. Therefore, as described by [9], for the determination of the moduli of elasticity from the specimens in tests, isotropy is assumed through the thickness of the plate. The characterization of the bending behavior, represented by the moduli of elasticity and rupture, is made by testing two groups of specimens extracted with their long dimensions parallel and perpendicular to the long dimension of the panel [21]. In the manufacturing process of laminated composites, the formation of residual stresses is inherently attributed to factors such as micro and macro-level, coupon-level, and component-level [22], which can cause a reduction in the mechanical performance of the composite produced [23e25]. Residual stresses lead to a reduction in the composite's service life, which can be explained by the action of penetrating

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liquids in microcracks formed by chemical and thermal shrinkage, as well as by the effects of warping and interface debonding [24,26]. For solid wood and its derivatives exposed to variations in humidity and temperature, dimensional variations with consequent formation of residual stresses are quite common. In pieces where the fibers are unidirectionally aligned, such as solid wood or glued-laminated timber, residual stresses are lower than in products whose fibers are crossed from one layer to another, such as OSB, crosslaminated timber, and plywood [27]. Given many materials applied in engineering and that can be used as constituents of the matrix and reinforcement phases, the mechanical behavior of the composite results from several factors, such as the nature of the components, fiber dimension, manufacturing, curing process, and application and exposure. In a wide universe of responses, computer models have been an effective and accurate option for estimating residual stresses and strains [28]. As finite element method (FEM) applications [29], used the modeling to validate the analytical models formulated to estimate the distribution of residual stresses in prestressed composites. Concerning the analysis of process-induced deformations and residual stresses, composites with curved parts were modeled by [25] and, despite relevant results shown with the adopted model, the need for new studies with more complex implementations was highlighted. Computational modeling is essential to better represent and evaluate the most complex behaviors of OSB panels since it allows concatenating the various factors associated with the workability and efficiency of this wood-based product. The FEM allows considering the particularities of each layer, with their specific properties, such as density, fiber direction, and void percentage, which also significantly influence the modulus of elasticity [30e32]. The relationships between properties of a material are commonly assumed for the implementation and adjustment of the numerical model for structural behavior. Based on this proposition, in the evaluation of the stress distribution along the OSB panel thickness [18], adopted the value of modulus of elasticity for each layer of the strands as a variable of the panel density profile. For a more accurate representation of the flexural behavior of wood elements [33e36], as wood exhibits elastic behavior in tension and elasticeplastic in compression, the models must not neglect the non-linearity of the material due to the crushing of compressed fibers, with consequent yielding. Concerning the wood-based products, the non-linearity of the material is treated, and its applications are reported, in several studies [37e39]. The use of simplified models, such as linear behavior, can lead to significant differences between modeling and experimental results. With the FEM to simulate an OSB sandwich panel [40], obtained a value of 6.5% higher for flexural rigidity than that determined experimentally. Because of these considerations, the establishing of a method that makes it possible to obtain the equivalent moduli of elasticity of each strand layer, that is derived from the flexural rigidity obtained by standardized bending tests for longitudinal and transverse directions of an OSB panel, will contribute to the provision of this very essential property for modeling with a multi-layer finite element. The main

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objective of this study was to estimate the equivalent moduli of elasticity to each OSB panel layer, with a results-based method of the specimens bending test in the longitudinal and transverse directions of the panel. Computational modeling by the Ansys software [41] with a multi-layer model was used to validate the results of this research, and physical non-linearity was considered for better adjustment of the models.

Materials and methods

2.1.

Manufacture of OSB panels for the study

To achieve the goal of this research, a total of eight OSB panels 400 400 mm in width were manufactured with strands of balsa wood (Ochroma pyramidale) waste glued with castor oil polyurethane resin (Pu-castor oil resin), that was applied at a content of 13% of the mass of wood particles. The thickness of 10 mm of the panels was composed at a layer proportion of 30:40:30 (outer - core - outer) resulting in a panel average density of 0.65 g/cm3, and the corresponding coefﬁcient of variation of 8.1%. The OSB panels were manufactured in Research Nucleus on Materials for Biosystems & Laboratory of Construction and Ambience (Faculty of Animal Science and ~ o Paulo, Brazil). Previously, Food Engineering, University of Sa Barbirato et al. [4] studied the feasibility of manufacturing OSB panels composed of balsa wood residues and Pu-castor oil resin, varying the density of the panels from 0.30 to 0.40 g/cm3 and the resin contents varying from 11 to 15%. The best physical and mechanical properties were proven for the composition with the highest density and resin content [4].

For the manufacture of the panels for this study (Fig. 1(ac)), with an intermediate resin content of 13%, strands with dimensions on the order of 90 25 1 mm were used at a moisture content of 8% previously achieved by drying for 48 h at a temperature of 65 C. The Pu-castor oil resin was applied by spraying and the biomass, arranged in a metallic mold, was pressed at 5 MPa for 10 min at 100 C. After 72 h in the ambient curing process, the panels were sanded, and ﬁnally, the specimens were cut following the Longitudinal (alignment axis for the length of the outer layer strands) and Transverse (transverse axis for the length of the outer layers strands) directions (Fig. 1(d)). The specimens cut with the long dimension aligned in the longitudinal direction were designated SL and, the specimens with the long dimension aligned in the transverse direction were named ST (Fig. 1(e)).

2.2. tests

Mechanical properties resulting from specimens

The parameterization of the models to represent the OSB panels behavior in the longitudinal and transverse directions was based on the results of specimens in static bending test at three points (Fig. 2 (a)) on a universal testing machine (Emic, Brazil). The load was applied at a constant crosshead speed of 6 mm/min on 10 specimens for each direction, according to the procedures described by European Standard EN 310 [42]. Taking into account the elastic region on the load versus deflection diagram comprised in the range of 10e40% of ultimate load according to ASTM D1037 [21], for the SL specimens the mean flexural rigidity value was 36,015,275.5 N mm2, with a respective coefficient of variation of 16.3%. For the ST group of specimens, a lower mean value for the flexural rigidity of

Fig. 1 e Manufacture process of OSB panel of residual balsa wood: (a) particle separator; (b) mattress of strands; (c) thermohydraulic press; (d) ﬁnished panel and orientation direction of the strands; (e) Longitudinal and Transverse specimens.

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2.3.

Fig. 2 e Test arrangements of specimens extracted from the OSB panels: (a) three-point static bending; (b) tension. 8,254,507.1 N mm2 was obtained and the coefficient of variation was 9.2%. The geometry of a specimen is properly of a wide-beam with the length of span (Ls) and cross-section defined by the width (b) and thickness (h). For each group of specimens (longitudinal and transverse), the specimen with the flexural rigidity (I E) closest to the average group value was chosen, and its measured dimensions were taken for modeling. For the longitudinal direction, the SL specimen with I EL¼ 34,193,390.0 N mm2, with its dimensions b ¼ 47.9 mm, h ¼ 10.8 mm and Ls ¼ 220 mm, was used for analysis. For the transverse direction, the ST specimen was used its measured dimensions being 49.4 10.4 220 mm and I ET equal to 8,291,020.8 N mm2. Based on these flexural rigidity values and the moment of inertia (I ¼ b h3/12 mm4), the moduli of elasticity were calculated, the results being EL ¼ 6812.3 MPa and ET ¼ 1796.8 MPa, for the longitudinal and transverse directions, respectively. The Poisson's ratios were determined based on the results of tension tests (Fig. 2(b)), with 10 specimens for each group (SP and ST) and standardized procedures [21]. These tests were performed on a universal testing machine (Emic, Brazil), with the load applied at a constant crosshead speed of the machine of 4 mm/min. The strain in the longitudinal and transverse directions was obtained with strain gages (Kyoa, KFG-20-120-C1-11, Japan), making it possible to calculate the mean value of Poisson's ratio for the longitudinal group (nL ¼ 0.31) and the transverse group (nT ¼ 0.13). In a study of OSB produced with strands of pine wood and phenol-formaldehyde resin, with the strands of the outer layers randomly distributed and the inner layer oriented along the length of the panel [43], was obtained, in tension, Poisson's ratios equal to 0.24 and 0.17, for the longitudinal and transverse directions of the panel, respectively. In the literature of the OSB panels, many other values can be found with variations for the major and minor Poisson's ratios, such as the values: 0.36 and 0.13 [44], or 0.30 and 0.11 [45]. The authors state that the Poisson's ratios of wood vary greatly due to the great variety of this material. In addition, other factors must also be considered, such as the type of adhesive and the orientation of the strands.

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Finite element modeling

To evaluate the results of the equivalent rigidity method, the specimens were modeled in the Ansys software [41], exploring the effects of each layer of the panel and the non-linearity of the material. Due to the panel's geometric characteristics (Fig. 3), the 3D SHELL181 element is formed by four nodes and suitable for modeling shell structures from thin to moderately thick having three degrees of translation and three degrees of rotation in each node, was used. Concerning the thickness of the panel, the option of multi-layer in the SHELL181 element enables considering the different properties for each layer of the composite. The modeling with multi-layer elements requires the assignment of the corresponding thickness and the mechanical properties for each of the oriented layers. For OSB panels formed by the three layers of strands through the thickness, two types of materials must be established to represent the properties due to the directions of the layers relative to the length of the specimens (direction X). For the SL specimen (Fig. 4(a)), representing the bending behavior of the panel according to the longitudinal direction, Material 1 was assigned to both outer layers and, Material 2 to the core layer. In the case of ST specimen modeling (Fig. 4(b)), Materials 1 and 2 must be applied to the core and both outer layers, respectively.

2.4.

Constitutive models for OSB

To implement the stress versus strain model, the elastic property of the material defining the elastic-linear segment must first be known, which in turn is represented by moduli of elasticity equal to 6812.3 and 1796.8 MPa, for the longitudinal and transverse directions, respectively. Subsequently, to represent the behavior of non-linearity of the material, the yield point must be defined. Based on the results of the bending tests with SL and ST specimens (Fig. 5), it was found that this point can be fixed at 60% of the maximum bending load. As shown in other studies, for the non-linear model, the yield point was indicated at a rate of approximately 60% of the ultimate compression stress [44]. The elasticeplastic relationship was proposed by segments in a multi-linear model for the range of 60e100% of the ultimate stress in compression (fcu), from which and to, a suggested

Fig. 3 e Mesh discretized by SHELL181 elements, with the representation of the supports at the ends of the span and the load application on key points positioned in the middle of the span of the specimen.

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Fig. 4 e Modeling of specimens in layers: (a) mesh and detail of the layers for SL; (b) mesh and detail of the layers for ST.

strain of 0.8%, the plastic behavior was assumed [44]. A stressestrain model with three linear segments was proposed by [10] for the OSB in bending and based on experimentally obtained results, with the segments corresponding to 0e40%; 40e80%, and 80e100% of maximum bending force. When modeling fiberboard plates, for the bi-linear model, Haj-Ali et al. [46] adopted the compressive yield strength equal to 60% of the tensile yield strength. When adjusting the model to represent physical nonlinearity, the value of the tangent modulus was obtained from the load versus deflection diagram, considering the experimental values corresponding to 60 and 100% of the maximum bending load (Pmax). In the longitudinal direction, this resulted in a tangent modulus equal to 4335.0 MPa, which, in the transverse direction, was 1193.5 MPa. In the longitudinal direction, for the value of 0.6 of the maximum bending load (0.6 Pmax ¼ 333.9 N), the bending moment was 18,364.5 N mm (0.6 Pmax Ls/4), and with an elastic section modulus of 931.18 mm3 (W ¼ b h2/6), the initial yield strength was 19.72 MPa. Based on this value, a bilinear model with an initial yield strength of 20 MPa was implemented (sigma20 model, Fig. 6(a)). This model, despite already accounting for the effects of non-linearity, had a much more rigid behavior compared to the experimental results. To adjust the model, the final displacement becomes more representative of the experimental value with an assumed initial yield strength of 10 MPa (sigma10 model). The multi-linear model is an interesting solution to better represent elasticeplastic behavior, and thus, resolve the differences found in the bi-linear models (sigma20 and sigma10). For the Mult_sigma15 model (Fig. 6(a)), implemented based on

attempts at adjustment, the following points (strain and stress) were assumed: (0; 0); (0.002202; 15); (0.00336; 20); (0.01;

Fig. 5 e Load-deﬂection models of the OSB material: (a) SL specimen; (b) ST specimen.

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For the transverse direction, with the bi-linear model, the initial yield strength estimated for a load of 123.18 N (0.6 Pmax), bending moment of 6775.9 N mm and W ¼ 890.52 mm3 was 7.61 MPa, and the value of 8 MPa was adopted for the sigma8 model (Fig. 6(b)). For this value, the behavior was more rigid than the experimental one, while for yield strength of 4 MPa, the bi-linear model was more adjusted to represent the maximum experimental displacement. For the multi-linear model, the ultimate stress corresponding to the maximum load of 205 N (Pmax) was estimated, resulting in 12.6 MPa, and the value of 10 MPa was adopted for the model. In this way, for the Mult_sigma5 model the corresponding points (0; 0), (0.0028; 5), (0.0053; 8), (0.0100; 10) were deﬁned (Fig. 6(b)). As for the model in the longitudinal direction, the model with multilinear adjustment was tested to obtain a better approximation of the experimental deﬂection (6.725 mm, Fig. 5(b)), resulting in a deformation of 2.3%, which was adopted for the Mult_sigma7.6 model (Fig. 6(b)).

2.5.

Fig. 6 e Stress x strain models: (a) SL specimen; (b) ST specimen.

30). The stress value corresponding to the plastic regime of 30 MPa was estimated with the relationship [bending moment/elastic section modulus]. In this case, for the maximum load of 556.5 N, the stress value was 32.9 MPa. Thus, for the point of a fully plastic regime, a deformation of 1% and stress of 30 MPa were adopted. The adjustment with the best approximation for an experimental deﬂection of 4.505 mm (Fig. 5(a)) was also tested, resulting in the Mult_sigma19.7 model (Fig. 6(a)), in which the elasticeplastic line was extended to deformation of 1.7%.

Equivalent moduli of elasticity of the OSB layers

The bending test according to ASTM D1037 [21] is easy to perform. It is used to obtain the elastic properties (I E) for the longitudinal and transverse directions of the OSB panels. However, these properties refer to the full thickness and not to each layer of the OSB panel. Nonetheless, computational modeling allows considering each layer of a composite, with its intrinsic properties. In this sense, based on the values EL and ET for bending the specimens extracted in the longitudinal and transverse directions, we sought to estimate the equivalent modulus of elasticity for each layer using a system of linear equations. For this purpose, the SL and ST specimens (Fig. 7) must be extracted from panels produced with identical materials, resin content, and moisture content. To set up the system of linear equations, the dimensions of the cross-section and the ﬂexural rigidity of each specimen were considered, and the equivalent moduli of elasticity were represented by ELL and ETL (Fig. 7), resulting in the system of equations (Eq. (1)).

Fig. 7 e Scheme of layers and parameters of the OSB panel to estimate the equivalent modulus of elasticity for each layer: (a) specimen cut with the long dimension aligned in the longitudinal direction; (b) specimen with the long dimension aligned in the transverse direction.

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Mult_sigma7.6 models were investigated, which include the maximum experimental displacements. For this purpose, the stress versus strain diagrams were modiﬁed based on the ratio of the moduli of elasticity (ELL/EL ¼ 1.05 and ETL/ET ¼ 0.79) that were applied to the stress values (Mult_layer model, Fig. 8).

The results concerning the rigidity obtained by the OSB models used in the computer simulations were evaluated based on the ﬂexural rigidity of the specimens in the bending test. Additionally, due to the proposed use of the equivalent moduli of elasticity attributed to the OSB panel layers, the effects in the normal bending stress were also evaluated. To validate the model discretized by SHELL181 elements (Fig. 3), the analysis of convergence was evaluated for several generated meshes by varying the number of nodes and elements. The results in Table 1 summarize the values of the deﬂections in the elastic-linear analysis for the maximum loads (Pmax) of 556.5 N (for SL) and 205.3 N (for ST), which were applied to three key points (2 edge points and 1 center point) positioned at the middle of the span of the specimen (Fig. 3). Based on the results of the convergence of vertical displacements with centesimal precision (Table 1), the mesh of the elements with dimensions of 2.5 mm was chosen for modeling for both directions.

Fig. 8 e Stress versus strain adjusted with physical nonlinearity and applied to the Mult_layer model: (a) longitudinal direction; (b) transverse direction.

(

2 ðIe Þ ELL þ Ii ETL ¼ I EL Ii ELL þ 2 ðIe Þ ETL ¼ I ET

Results and discussion

(1)

where Ie is the moment of inertia of each outer layer, Ii the moment of inertia of the core layer, I the moment of inertia of full cross-section, EL and ET the modulus of elasticity obtained from the bending test with the length of the specimens aligned in the longitudinal and transverse directions, respectively, ELL the equivalent modulus of elasticity of the longitudinal layer and ETL the equivalent modulus of elasticity of the transverse layer. As the resolution of the linear system results only in elastic properties, to consider the effects of non-linearity of the material, the adjustments for the Mult_sigma19.7 and

Table 1 e Mesh attributes and maximum vertical displacements for SL and ST specimens, corresponding to Pmax. Elements Dimension (mm) 20 10 5 2.5 1

Deﬂection (mm) Quantity

48 132 440 1760 10,560

3.66 3.67 3.70 3.70 3.70

5.52 5.55 5.56 5.57 5.57

Fig. 9 e Deﬂection as a function of the step of maximum loads for the various models tested: (a) longitudinal direction; (b) transverse direction.

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of the experimental value. The sigma8 and sigma4 models were inadequate for the final loading steps and in the range of 60e90% of Pmax, respectively. The multi-linear models showed the possibility of almost exact adjustments, with the greatest difference being registered in Mult_sigma7.6, for a load range close to 75% of Pmax. Non-linearity is essential in the model for the behavior of wood-based products to bending and its effects are strongly amplified for load levels closer to the maximum. The experimental results of this study corroborate the adoption of models in which the non-linearity is represented by straight lines, in the so-called multi-linear model. For the first stage, which consists of defining the straight-line segment coinciding with the elastic-linear phase, based on the tests, we adopted the validity for 60% of the maximum bending load. However, other experimental researches show that this point can be in a range of 40e60% of the maximum load [10,45]. This difference can be explained by the nature of this composite, whose mechanical and physical behavior depends on several factors, such as the type and content of adhesive wood species, and panel densification.

Fig. 10 e Step of maximum load versus deﬂection with nonlinearity applied to the layered model (a) Longitudinal (b) Transverse.

3.1.

Modeling with non-linear behavior

The flexural rigidity analysis was based on the evaluation of how representative each model implemented for the panel behavior was, to the experimental results of load versus deflection. For the longitudinal direction (Fig. 9(a)), the purely elastic-linear model (Elastic-linear) resulted in behavior that can be accepted up to a certain level of the maximum load (approximately 80% of Pmax), followed by the results of a very rigid model with maximum displacement 79.8% lower than the experimental one. The results obtained with the sigma20 model were very similar to those obtained with the Elasticlinear model, not representing the behavior for more advanced step loads. The sigma10 model was adjusted to represent the maximum experimental displacement value. On the other hand, there was a range in which the displacements were greater than the experimental ones, this was observed for loading from approximately 60% of Pmax. Both the Mult_sigma15 and Mult_sigma19.7 models were very representative of the material's behavior, being virtually equal for all step loads. Of these models, it must be considered that Mult_sigma19.7 benefits from simpler implementation procedures to the stressestrain relationship. For the transverse direction, the behavior of each model (Fig. 9(b)) was remarkably similar to those when applied in the longitudinal direction, in which the maximum vertical displacement obtained with the Elastic-linear model was 81.3%

Fig. 11 e Maximum bending stress for SL specimen - case with a single-layer [MPa]: (a) tension in direction X (b) compression in direction X (c) tension in direction Z (d) compression in direction Z.

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Fig. 12 e Layered SL and detailing of the normal stress distributions in two elements positioned in the center of the specimen [MPa]: (a) stress in direction X (b) stress on three layers in direction X (c) stress on three layers in direction Z.

The comparison of the results of computational modeling with the experimental ones allows inferring the most appropriate multi-linear models for representing the OSB panels’ vertical displacements. Based on these considerations, the multi-linear model was adopted in this research.

3.1.1. Validation of the model with equivalent moduli of elasticity of strands layers For SL and ST specimens manufactured with a layer proportion of 30:40:30, represented generically in Fig. 7 and with the static bending test data shown in Table 2, the resolution of the linear equation system (Eq. (1)) resulted in values of the equivalent moduli of elasticity of 7167.7 MPa (ELL) and 1422.7 MPa (ETL). To validate these results, the specimens were modeled in two cases: with a single-layer (with the modulus of elasticity obtained directly from the bending test) and with three layers (with the corresponding equivalent moduli of elasticity). In the case of the SL modeled with a single-layer, the following properties were considered: EL ¼ 6812.26 MPa and nL ¼ 0.31. In the case of the ST model with a single-layer: ET ¼ 1796.75 MPa and nT ¼ 0.13 were considered. For the layered modeling, in the case of the SL specimen (Fig. 7(a)), in the outer layers the Material 1 (ELL ¼ 7167.7 MPa and nL ¼ 0.31) was applied, and in the core layer the Material 2 (ETL ¼ 1422.7 MPa and nT ¼ 0.13) was used. For the layered case (Fig. 7(b)), the outer and core layers were assigned Material 2 and Material 1, respectively. Based on the results obtained in the linear analysis and compared to the single-layer model (Table 3), it is possible to note that the layered model for the longitudinal direction resulted in higher deﬂections for each step load; however, the

differences were only 2.2%. For the transverse direction, the model with a single-layer resulted in higher deﬂections (0.5%) than the situation with layers discretized. The differences of 2.2 and 0.5% in the SL and ST cases are insigniﬁcant, which allows validating the proposal for estimating the layers elastic properties, based on the results of bending tests, obtained from the ratio of the moduli of elasticity (ET/EL ¼ 0.264 and ETL/ELL ¼ 0.198). The method was also applied to the data published by [6] for OSB panels made of Eucalyptus grandis wood with Phenol-Formaldehyde resin in the proportion of 20:60:20, for which the ratio of the moduli of

Table 2 e Mechanical and geometric parameters of the specimens. Parameters

I E (N mm2) h (mm) b (mm) e (mm) i (mm) Ie (mm4) Ii (mm4) I (mm4) ce (mm)

34,193,390.0 10.8 47.9 3.2 4.3 2353.3 321.8 5028.4 3.8

8,291,020.8 10.4 49.4 3.1 4.2 2167.2 296.4 4630.7 3.6

Where I E is the ﬂexural rigidity, h the full panel thickness, b the width, e the thickness of the outer layers, i the core layer thickness; Ie the inertia moment of each outer layer; Ii ¼ inertia moment of the core layer, I the inertia moment of full cross-section, ce the position of the center of gravity of the outer layer concerning the neutral axis of the panel (on half-thickness).

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Table 3 e Deﬂections (mm) for modeling of SL and ST, single and layered model. SL

P/Pmax

0.2 0.4 0.6 0.8 1.0

Singlelayer

Threelayers

Singlelayer

Threelayers

0.74 1.48 2.22 2.96 3.70

0.76 1.51 2.27 3.02 3.78

1.11 2.23 3.34 4.46 5.57

1.11 2.22 3.33 4.44 5.54

elasticity were ET/EL ¼ 0.571 and ETL/ELL ¼ 0.350. In this case, considering this is a composite product with different layer proportions and material characteristics than those of the present study, the results were also very satisfactory, with deflection differences resulting in 0.56 and 0.76% for the longitudinal and transverse directions, respectively. The differences between the moduli of elasticity from one layer to another can be significant when the type of adhesive and their density are different. This was shown in an experimental study by [20], in which specimens were cut from the inside of each layer of commercial panels, produced with a thickness of 18 mm, with adhesives from the outer layers (melamine-urea-phenol-formaldehyde) and the inner layer (methylene-diphenyl-diisocyanate) and, with the density of the outer layers 40% higher than the density of the inner layer. The tests resulted in the values of the moduli of elasticity of the outer layers (5148 and 4845 MPa) and the inner layer (2314 and 1666 MPa). The importance of means to determine the properties for each layer of the OSB panel was highlighted [20], as well as the difficulties in cutting specimens from the inner of each layer, and that greater homogeneity is expected for a smaller thickness of the OSB. In these aspects, the relevance of the present study must be highlighted, providing a method to obtain the equivalent moduli of elasticity to be applied, in computational modeling design.

3.1.2.

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it was found that, concerning the experimental results, deflection increased from 0.85 Pmax onward, reaching a deflection of 5.02 mm for the maximum load, 11.3% higher than the experimental correspondent. Because the Mult_layer model is derived from the Mult_sigma19.7 model, the difference between both occurred only for the most advanced stage of the non-linear curve segment. The use of the Mult_layer model for ST (Fig. 10(b)) resulted in a maximum deflection of 6.64 mm, which represents 98.7% of the maximum experimental value (6.73 mm). For all step loads, it was also found that this model was virtually identical to the Mult_sigma7.6 model (Fig. 9(b)) and well adjusted to the experimental results (Fig. 10(b)).

3.2. Normal bending stress considering single and multi-layer models 3.2.1.

SL specimen modeled - normal stress

The normal stress was obtained considering the maximum load of 556.5 N applied in the SL specimen in the bending test. The

Non-linearity applied to the layered model

SL and ST specimens were modeled based on the results of the layers' elastic properties and on the implementation of the adjusted non-linear models (Fig. 8). In the ﬁrst case (Fig. 10(a)),

Fig. 13 e Normal bending stress versus load e SL specimen, with single-layer and layered models.

Fig. 14 e Maximum bending stress for ST specimen e single-layer [MPa]: (a) tension in direction X (b) compression in direction X (c) tension in direction Z (d) compression in direction Z.

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Fig. 15 e Layered ST and detailing of the normal stress distributions in two elements positioned in the center of the specimen [MPa]: (a) stress in direction X (b) stress on three layers in direction X (c) stress on three layers in direction Z.

results were obtained with the Mult_sigma15 (Fig. 6(a)) and Mult_layer model (Fig. 8(a)). In direction X, aligned with dimension Ls, when modeling with Mult_sigma15, the maximum bending stress values for the maximum load were 27.3 MPa (tension on bottom face), and compression was 27.3 MPa (top face), as shown in Fig. 11(a-b). The value calculated based on the elasticity theory equation (material with elastic-linear behavior) was 32.9 MPa, thus being 20.5% higher than that obtained by the non-linear computational model adjusted for vertical displacements. In direction Z (Fig. 11(c-d)), which represents the width of the specimen, the maximum values of tension and compression were 4.1 MPa (bottom and top faces). Although these values are lower than in the other direction, this was expected due to the geometric characteristics and static scheme of the specimen (as a wide-beam). During the bending test, the rupture was well characterized in the central region of the specimen, where the highest values of the normal bending stress were obtained. For the Mult_layer model (Fig. 12), both in the X and Z directions, the maximum stress occurs on the outer faces of the specimens because of their association with the material with the greatest modulus of elasticity. Unlike the specimen modeled as a single-layer (with the rigidity of the bending test), in the case with discretized layers, the distribution of

stress along the panel's thickness (Fig. 12(b-c)) allows the optimization of the panels regarding their layer composition, e.g., by changing the layer thickness. Considering the values of the normal bending stress to the step loads (Fig. 13) allows visualizing the effects of nonlinearity for both models (single-layer and multi-layer). Direction X shows a reduction in the growth rate of such stress given the increase in applied load. Comparatively, for the single-layer model to the layered model and the maximum load, in directions X and Z, the maximum stress differences were 5.4 and 25.2%, respectively. Of these values, the case of direction X is more critical for meeting the types of panels standardized, for example by EN 300 [47].

3.2.2.

ST specimen modeled e normal stress

In the bending tests with the dimension Ls in the transverse direction (ST specimen), the maximum load value was 205.3 N, for which the maximum stress estimated was 12.7 MPa. With the Mult_sigma5 model (Fig. 6(b)), for direction X which is aligned to Ls, the maximum tension and compression stress obtained (Fig. 14(a-b)) was 10.6 MPa (bottom and top faces). Regarding this value, the result estimated with the supposedly elastic-linear case was 19.8% higher,

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panel, should be evaluated as accurately as possible for any position of the panel's layer.

Fig. 16 e Normal bending stress versus load e ST specimen, with single-layer and layered models.

remarkably similar to what happened for the longitudinal direction. For direction Z (Fig. 14(c-d)), the maximum tension and compression stress obtained was 1.6 MPa. In the ST specimen modeled with Mult_layer (Fig. 15), the maximum stress occurred on the faces of the core layer. This understanding of the stress distribution, especially on the transition surfaces, can be useful for the analysis of the failure in the interface of the layer. In this region, with an equivalent modulus of elasticity ratio of 0.2% (ETL/ELL), and for the maximum bending load, from the core to the outer layer, the stress varied abruptly by 204% (24.13e7.93 MPa) and 269% (5.02e1.36 MPa), in directions X and Z, respectively. The effects of the non-linear model applied for the discretized layers impacted the normal bending stress obtained for each step load (Fig. 16), being signiﬁcant for the more advanced step loads. For the maximum bending load, the reduction in the normal stress was 24.9% (direction X) and 13.4% (direction Z). For both specimens, the greatest differences between the single-layer and layered models were registered for load intensity closer to the maximum value, being affected by the model adopted for non-linearity. This suggests that other considerations and adjustments may be implemented in future studies. The values of the maximum normal stress calculated from the results of bending tests, 32.9 MPa (SL) and 12.7 MPa (ST), as well as the stress estimated by the computational models, 27.3 MPa (SL) and 10.6 MPa (ST), showed that the panel manufactured with balsa wood waste with Pu-castor resin (the content of 13%) meets the minimum requirements standardized by [47] for OSB/1 panels (for general uses in dry environments, including use as furniture). For this type of OSB panel, the minimum moduli of elasticity of 20 and 10 MPa are established, in the respective longitudinal and transverse directions to the panel. Additionally, the equivalent moduli of elasticity method should also be investigated in future studies to evaluate the efforts in panels manufactured with densities and types of adhesives, different from one layer to another. To specimens cut from the layers of panels thus constituted and tested by tension [20], was obtained maximum stress to the outer layers 2.43 times greater than that of the inner layer. This difference, which can be decisive in checking the maximum load of the

Conclusions

In this study, exploring results of static bending tests of OSB panel specimens manufactured with balsa wood waste and organic adhesive (Pu-castor oil resin), a method has been established to obtain the equivalent moduli of elasticity to each panel layer. The method was consolidated by a system of equations derived from geometric and elastic parameters. To adjust and validate the model, the FEM was used to evaluate the deflections and shown excellent results, including in predicting the deflections of OSB panels manufactured with another material composition (wood species and phenolic resin). Because of the non-linearity of the material, the main differences found between the computational modeling results and the deflection experimental results were better treated with multi-linear function adjustments for the stressestrain relationship. It is suggested that the elastic-linear behavior is allowed up to the values close to 60% of the ultimate stress. In the models adjusted for layered simulation, with the initial yield point and total yielding stress modified by the ratio of the moduli of elasticity equivalent and experimental, the differences in the normal bending stress were stronger from the elasticeplastic phase. This makes it possible to consider that the adjustment of the behavior of non-linearity can be improved by other parameters of the material not addressed in this stage of the research. In this sense, it is suggested that further research be developed with approaches and treatments for models that can also assess the effects of residual stresses, with the features of this material. The computational modeling with the application of layer properties benefited the obtaining the results for the stress analysis, with details for any position within the thickness of the panel. It is a required application in designs to evaluate the agreement of mechanical performance standards for this type of material. The method established for calculating the equivalent moduli of elasticity, based on the results of the static bending test and with the applied adjustment to the non-linearity, evidenced a good agreement to assign these properties to OSB panel layers.

Declaration of Competing Interest The authors declare that they have no known competing ﬁnancial interests or personal relationships that could have appeared to inﬂuence the work reported in this paper.

Acknowledgements The authors thank FAPESP (ordinance 2017/18076-4). Coor~ o de Aperfeiçoamento de Pessoal de Nı́vel Superioredenaça Brazil (CAPES) e ﬁnance code 001. CNPq (ordinance 372

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407451/2018-8 and ordinance 304106/2017-8). The authors also -Reitoria de Pesquisa e UNIthank Espaço da Escrita e Pro CAMP e for the language services provided.

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Phosphomolybdic Acid-Catalyzed Oxidative Degradation of Waste Starch: A New Strategy For Handling The Pulping Wastewater YONGZHEN QIAO, WEISHENG YANG, XIU WANG, LIANG JIAO, YIQIN YANG, SHUMEI WANG, HUIYANG BIAN & HONGQI DAI. When old corrugated cardboard (OCC) is returned to the paper mill for repulping and reuse, the starch, which is added to the paper surface as a reinforcement agent, is dissolved into the pulping process water. Most of the OCC pulping wastewater is recycled to save precious water resources; however, during the water recycling process, the accumulation of dissolved starch stimulates microbial reproduction, which causes poor water quality and putrid odor. This problem seriously affects the stability of the papermaking process and product quality. In this study, phosphomolybdic acid (H 3PMo12O40, abbreviated as PMo12) was utilized to oxidatively degrade the waste starch present in papermaking wastewater to monosaccharides, realizing the resource utilization of waste starch. The results showed that the optimized yield of total reducing sugar (73.54 wt%) and glycolic acid (11.05 wt%) was achieved at 145°C with 30 wt% PMo12, which is equivalent to 84.59 wt% starch recovered from wastewater. In addition, the regeneration of the reduced PMo12 was realized applying a potential of 1 V for 2 h. Overall, this study has theoretical significance and potential application value for resource utilization of waste starch in OCC pulping process and cleaner management of OCC waste paper. Contact information: Nanjing Forestry University, China. Research article preprint. https://doi.org/10.21203/rs.3.rs-231180/v1 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 17

Article 8 – Wastewater Treatment

Phosphomolyybdic Acid-C Catalyyzed Ox Oxiidative Degradation of Waste Starch: A New Strategy For Handliing The Pulp ping Wastewater Yongzhen Qi Qia ao Nanjing Forestry University Weisheng Yang Nanjing Forestry University Xiu Wang Nanjing Forestry University L ia n g J ia o Nanjing Forestry University Yiqin Yang Nanjing Forestry University S humei Wang Nanjing Forestry University Huiyang Bian Nanjing Forestry University Hongqi D ai (  hgdhq@njfu.edu.cn ) Nanjing Forestry University

Research Article e Keywords: OCC waste paper, Waste starch, Phosphomolybdic acid, Reducing sugar, Recycle utilization Posted D ate: February 25th, 2021 D OI OI:: https://doi.org/10.21203/rs.3.rs-231180/v1 License:   This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License

Page 1/16

Ab bstract When old corrugated cardboard (OCC) is returned to the paper mill for repulping and reuse, the starch, which is added to the paper surface as a reinforcement agent, is dissolved into the pulping process water. Most of the OCC pulping wastewater is recycled to save precious water resources; however, during the water recycling process, the accumulation of dissolved starch stimulates microbial reproduction, which causes poor water quality and putrid odor. This problem seriously affects the stability of the papermaking process and product quality. In this study, phosphomolybdic acid (H3PMo12O40, abbreviated as PMo12) was utilized to oxidatively degrade the waste starch present in papermaking wastewater to monosaccharides, realizing the resource utilization of waste starch. The results showed that the optimized yield of total reducing sugar (73.54 wt%) and glycolic acid (11.05 wt%)was achieved at 145 °C with 30 wt% PMo12, which is equivalent to 84.59 wt% starch recovered from wastewater. In addition, the regeneration of the reduced PMo12 was realized applying a potential of 1 V for 2 h. Overall, this study has theoretical signi cance and potential application value for resource utilization of waste starch in OCC pulping process and cleaner management of OCC waste paper.

In ntroduction In the production of corrugated paper and liner paper, starch is often used as a paper surface enhancer because of its low cost, environmental protection, and degradability (Li et al. 2013; Wang C 2020). However, when the old corrugated cardboard (OCC) waste paper made from corrugated cardboard boxes and test liner is returned to the paper mill for pulping and papermaking, most of the starch on the paper surface is dissolved into the water during dissociation of waste paper bers. The starch, which accumulates abundantly in the papermaking system, has a serious effect on the papermaking production, particularly regarding environmental impact, stability of the system operation, and product quality. Simultaneously, the accumulated starch also causes proliferation of microorganisms(Zhu et al. 2017), which results in rot and smell and further deterioration of the production system, the environment, and product quality (Lin et al. 2020; Miao et al. 2012). Generally, anaerobic fermentation is used for the production of biogas, wastewater treatment, and energy recovery (Chaterjee et al. 2019; Sun et al. 2011). According to the China Paper Association report in 2019(Association 2020), the total production of corrugated cardboard containers in China is 44 million tons, accounting for 40.9% of total paper production. Commonly, starch consumption is approximately 40–60 kg for every ton of paper bers; the total consumption of starch based on the above reports is 1.76–2.64 million tons every year, which is equivalent to 303,000~455,000 ha of elds (the average yield of corn starch is 5800 kg/ha)(Lin et al. 2020). This implies the wasting of a large amount of food. Polyoxometalates (POMs) are polymetallic oxygen cluster compounds consisting of a metal–oxygen octahedron, which have become a research hotspot in many elds due to their low corrosivity and environmental protection (Guo et al. 2019; Wang and Yang 2015). POMs are considered as water-soluble metal oxide nanoparticles (Du et al. 2017; Wu et al. 2016), and have both acidic and redox characteristics, as well as unique "pseudo-liquid phase" characteristics (Long et al. 2010). Therefore, it is more e cient Page 2/16

for catalyzing the reactions. These compounds can be redox active in solution by electrochemical oxidation because of its multielectron property, while their anion structure is preserved (Chen et al. 2019; Glass et al. 2016). POMs have been used for the degradation of biomass (Albert et al. 2012; Bosco et al. 2010; Zhang et al. 2012). Thus, Liu et al. used phosphomolybdic acid (H3PMo12O40, abbreviated as PMo12) to degrade biomass such as cellulose and starch into small molecules of sugars and organic acids (Liu et al. 2016). Tian et al. hydrolyzed cellulose with phosphotungstic acid (H3PW12O40) at 180 °C for 120 min. The glucose yield was more than 50% with 92.3% glucose selectivity, and few byproducts were obtained (Tian et al. 2010). Starch and cellulose are high molecular polymers formed by dehydration of glucose units (Buléon et al. 1998; Goodman 2020). Therefore, POMs can be used to hydrolyze starch to produce reducing sugar (RS) (Mamman et al. 2008; Mua and Jackson 1997) and glycolic acid(Zhang et al. 2012), having demonstrated excellent electrochemical performance on the degradation of biomass. Herein, recycled waste starch (WS) in OCC pulping process water was oxidized and degraded using PMo12. The in uencing factors, namely, reaction temperature, time, and PMo12 usage, on the production of RS and glycolic acid from WS were evaluated. Furthermore, the recycling performance of PMo12 after electrooxidation regeneration was analyzed. The feasibility of turning WS to RS and glycolic acid using PMo12 was studied. The speci c experimental process is presented in Fig. 1. This work is expected to provide a theoretical guidance and application reference for realizing resource utilization of WS in the OCC pulping process water and developing clean papermaking production.

Materials s And Methods Materials s WS from OCC pulping process water was provided by Nine Dragons Paper Co., Ltd (Taicang, China). PMo12 was supplied by Shanghai Aladdin Chemicals Co., Ltd. (Shanghai, China). Glucose (AR), cesium chloride (CsCl, AR), and diethyl ether (AR) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). 3, 5-Dinitrosalicylic acid (DNS) was prepared according to a previous work (Adeogun et al. 2019; Miller 1959). Curve determination of glu ucose standard solu ution Glucose (1 g) was added to a volumetric ask, and deionized (DI) water was added to obtain a volume of 1 L. From this solution, which was labeled as standard solution, 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL was taken respectively, supplemented with DI water to 1 mL, and 2 mL DNS was added. After reaction in boiling water bath for 2 min, the solution was placed in an ice water bath. Finally, the reaction solution was xed to 15 mL. The absorbance of the mixture was measured using a UV757CRT Model spectrophotometer at 540 nm (Miller 1959; Tian et al. 2010). The DNS reagent reacted with RS to form 3-amino-5-nitrosalicylic acid. The product was brownish red under boiling condition, and the color was proportional to the RS content in a certain concentration range. Page 3/16

Se eparation of waste starch in OC OCC C pulp ping wastewater The wastewater from the multi-disc thickener in the OCC re-pulping was ltrated by Busher funnel with 325 mesh rstly. Then, the ltration was centrifuged at 4500 rpm for 20 min using a high-speed centrifuge. The supernatants were subsequently placed in a dialysis bag with MW-CO 8000– 12000(D).Then, a water-soluble organic solution (waste starch and water-soluble organic matter) without the inorganic substances was obtained. The concentration of WS was measured with amylase by HPLC(Lin et al. 2020). Hydrothermal reaction of WS with PMo12 WS was easily oxidized and degraded by PMo12 under hydrothermal conditions. The hydrothermal treatment was conducted in a 250 mL three-port ask reactor equipped with a stirring device and a condenser. A WS solution was prepared and transferred to the reactor, to which a certain amount of PMo12 was added. Then, the mixture was heated in an oil bath to the desired temperature with a stirring speed of 300 r/min. The effect of hydrothermal temperature was investigated at 140 °C, 145 °C, 150 °C, 155 °C and 160 °C, and the PMo12 dosage based on WS was investigated from 20 to 80 wt% for 60, 120, 180, and 240 min. Under direct heating, the solution gradually changed from yellow to dark blue. Then, 5 mL of sample was taken every 60 min for standby sampling and diluted to 1 mmol/L, and the reduction degree of PMo12 was determined simultaneously by absorbance spectrophotometry at 700 nm. To this aim, the standard curve of the reduction degree versus absorbance of PMo12 was obtained by titrating a PMo12 solution with a KMnO4 standard solution (0.01 mol/L). D etermination of total reducing sugar content after the hydrothermal reaction The PMo12 present in the mixture after the hydrothermal reaction was removed. After addition of a slight excess CsCl, a precipitate was immediately generated. The upper solution was cleared by centrifugation. Then, the supernatants were ltered through a lter with a pore size of 0.22 μm, and the ltered liquid contained the total reducing sugar (TRS). Then, a mixture containing 2 mL of DNS reagent and 1 mL of ltrate was heated in a boiling water bath for 2 min, and 12 mL of DI water was added after the mixture was cooled down to room temperature. The color intensity of the mixture was measured in a UV757CRT Model spectrophotometer at a wavelength of 540 nm. The concentration of TRS was calculated according to a standard curve obtained from the concentration of glucose using Equation 1.

where c denotes the concentration of TRS, v is the volume of TRS, and m represents the WS mass. The concentrations of glycolic acid, 5-hydroxymethylfurfural (5-HMF), levulinic acid, and formic acid were quantitatively determined by an external standard method; then, their quantities in the liquid products of hydrolysis were calculated according to the liquid yields. The concentration of the liquid products in the Page 4/16

ltrate was determined by HPLC using an Aminex BioRad-HPX-87H column and a refractive index detector. The mobile phase was 5 mM H2SO4, the ow rate was 0.6 mL/min, and the column temperature was 55 °C. Two parallel assays were performed for each experiment. Electrochemical oxidation of PMo12 The electrolysis cell was composed of a high-density graphite plate with a serpentine groove, a Na on 115 membrane, a silicone gasket, a platinum sheet as cathode, and graphite felt as anode. The bipolar plates of the cell were high-density graphite plates with a serpentine ow channel 2 mm wide, 5 mm deep, and 50 mm long (the total geometry projected area of the channel was 1 cm2 ), which is schematically illustrated in Fig. 2. The graphite felt was pretreated with concentrated HNO3 and H2SO4 in a 1:3 volumetric ratio at 50 °C for 30 min. Then, the graphite felt was washed with DI water until the pH of the wash water became neutral, dried at 80 °C, and cut into pieces with the thickness of 5 mm and width of 2 mm. These graphite felt electrodes were lled into the channel of the anode (Liu et al. 2014a). Diethyl ether was added to the dark blue waste starch–PMo12 solution after the hydrothermal reaction. PMo12 was extracted to the upper layer after full shaking (Okuhara 2002; Tian et al. 2010). When the diethyl ether was completely volatilized using rotary evaporator, PMo12 was dissolved in DI water. The PMo12 solution was then pumped into the anode, and the phosphoric acid aqueous solution (1 mol/L) was pumped into the cathode side of the cell. A potential of 1 V was applied by an electrochemical workstation for electrooxidation. From the solution, a sample was collected every 1 h and diluted to 1 mmol/L for analysis of the reduction degree of PMo12 by spectrophotometry.

Resultts And Discussion Analyysis of the factors in uencing the oxidative degradation of WS The factors determining the oxidative degradation of WS include reaction time, temperature, pH of the reaction system, and concentration of reactants (Girisuta et al. 2007; Mukherjee et al. 2016). We conducted single-factor experiments to select the three main factors, i.e., reaction temperature, PMo12 dosage, and reaction time, in a targeted manner, and obtained the optimal process conditions for determination of the TRS yield. First, the standard curve of this experiment was adjusted to zero with the color reaction solution of DI water as control, and the standard working curve was drawn with the mass fraction of glucose as the abscissa and the absorbance as the ordinate (Fig. 3a). The regression equation was y = 0.0185x + 0.1074 (R2 = 0.9980), where R2 is the correlation coe cient and de nes the feasibility of the method and the degree of linear relationship. Generally, R2 > 0.99 ensures an appropriate limit of error. The DNS reagent was used to determine the TRS content in the experiment. Effect of reaction temperature on TRS and glyycoliic acid yield d

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Here, the measured concentration of WS was about 5 g/L by HPLC. Thus, in all experiments, 5 g/L, 100 mL of WS ltrate was applied. 20 wt% of PMo12 and 120 min of reaction time were applied in this part. As shown in Fig. 3b, the TRS yield increased and then decreased with increasing the reaction temperature. The highest TRS yield of 62.98 wt% was obtained at 145 °C; the highest yield of glycolic acid was 16.45 wt% at 160 °C. Then, with further increasing the reaction temperature to 160 °C, the yield rapidly decreased to 33.63 wt%, which was 46.60% lower than that at 145 °C. On the contrary, the increase of glycolic acid was 4.92 wt% from 145 °C to 160 °C. Therefore, it can be concluded that the reaction temperature was an important factor that restricts the conversion of starch into RS, and had a great in uence on the TRS yield, meaning that starch could not be fully hydrolyzed to RS at lower temperature. However, as the temperature increased, the oxidation of PMo12 played a major role, and the oxidative degradation of RS was violent. In acidic solution at a high temperature, RS was the intermediate substance in the process of WS degradation, and was easily degraded in acid medium to produce insoluble humins and other byproducts (Yu et al. 2017). Basically, to prevent ineffective degradation of starch, the optimization reaction temperature is 145 °C, the sum of TRS and glycolic was 74.91 wt%. Effect of PMo12 dosage on TRS and glyycoliic acid yield d Apart from the effects of temperature and time, the dosage of PMo12 also had a signi cant in uence on the hydrolysis of WS to glucose. The acidity of PMo12 accelerates the hydrolysis of WS, and the oxidation contributes to the cleavage of chemical bonds of WS, driving the reaction forward. Different TRS yields were obtained by changing the PMo12 dosage (20, 30, 50, and 80 wt%) at 145 °C for 120 min. For a dosage of 20 wt%, most degradation was observed, and the TRS yield was only 62.98 wt% (Fig. 3c). Fortunately, the TRS yield increased rapidly to 73.54 wt% and 75.83 wt%, and the glycolic yield was 11.05 wt% to 12.99 wt% when the PMo12 dosage was 30 to 50 wt%, respectively. However, the TRS yield did not increase signi cantly with further increasing the PMo12 dosage. Hence, from the perspective of environmental protection and economy, the optimal reaction condition was 30 wt% PMo12, which afforded a TRS yield of 73.54 wt% and 11.04 wt% yield of glycolic acid. Effect of reaction time on TRS and glyycoliic acid yield d With the optimized reaction temperature and PMo12 dosage in hands, which were 145 °C and 30 wt%, respectively, the TRS yield was explored at different reaction times. We found that the TRS yield increased rst and then decreased with the reaction time (Fig. 3d). This was because the RS was further degraded under high temperature and acidic conditions. Simultaneously, organic degradation products such as glycolic acid, 5-HMF and formic acid were generated. With increasing the reaction time, the C–C bond cleavage effect of PMo12 increased(Khenkin and Neumann 2008), which favored the production of levulinic acid and formic acid. Although the TRS yield was only 0.57 wt% higher at 180 min than at 120 min, the reaction time increased by 60 min. Consequently, the TRS yield was reduced. The optimized TRS yield of 73.54 wt% was obtained for 120 min reaction time. In conclusion, the optimal conditions for the

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catalytic hydrothermal process to achieve a TRS yield of 73.54 wt% were 145 °C reaction temperature, 30 wt% PMo12, and 120 min reaction time. Mechanism of the PMo12-catalyyzed oxidative degradation of starch As shown in Table 1, the main product of starch degradation using PMo12 was TRS, and a small number of byproducts (e.g., glycolic acid, 5-HMF, formic acid, and levulinic acid) were detected by HPLC(Deng et al. 2012). Table 1 Products analysis of oxidation degradation of WS by PMo12 Conditions (T/ °C)

Main products TRS (wt%)

Glucose (wt%)

Glycolic acid(wt%)

5-HMF (wt%)

Formicacid(wt%)

140

46.57 ± 2.67

26.02 ± 2.53

5.34 ± 2.77

0.19 ± 1.08

145

62.98 ± 3.11

31.39 ± 2.87

11.93 ± 2.43

0.43 ± 2.13

150

58.76 ± 2.32

28.72 ± 2.43

14.18 ± 2.45

0.88 ± 2.19

0.83 ± 2.07

155

48.43 ± 3.42

23.46 ± 3.11

15.12 ± 2.54

1.42 ± 3.41

1.63 ± 1.99

160

33.63 ± 2.67

13.91 ± 2.87

16.45 ± 2.77

1.90 ± 3.15

2.49 ± 2.16

Notes: 5 g/L WS, 20 wt% PMo12 (PMo12/WS mass ratio), 120 min reaction time. Fig. 4a, b display a plausible reaction mechanism for the PMo12-catalyzed oxidative degradation of starch. The branched macro-molecule amylopectin and the linear macromolecule amylose, which consists of crystalline and amorphous lamellae of starch, form a semi-crystalline structure in the starch granule(Farias et al. 2020). It means that starch contains a large number of α-1, 4 glycosidic bonds and fewer α-1, 6 glycosidic bonds. The –O–H, C–O–C, and C–C bonds in starch molecular chain are cleaved due to the strong Brønsted acidity and oxidation properties of PMo12(Li et al. 2012; Liu et al. 2014a; Liu et al. 2014b). Thus, H+ ions penetrate into the starch molecule in the hydrothermal reaction process, cleaving the α-1, 4 and α-1, 6 glycosidic bonds. Moreover, the amorphous region of starch likely undergoes cleavage reaction affording the hydrolysate RS, which is mainly composed of monosaccharides. In the oxidative degradation stage of PMo12 and starch macromolecules, a hydrogen bond is formed between a free –OH in the starch molecule and an O atom of Mo–O in PMo12 (Fig. 4a). Meanwhile, a proton and an electron are provided to PMo12 by the starch molecule. Then, an O–H covalent bond is formed between free –OH and Mo–O at high temperature. On the one hand, the glucose Page 7/16

is converted to 5-HMF by isomerization and dehydration. Furthermore, part of 5-HMF continues to generate formic acid and levulinic acid via decarboxylation. On the other hand, the glycolaldehyde and erythrose are oxidative intermediate byproduct from the retro-aldol fragmentation of glucose, and are continuously oxidized to glycolic acid(Zhang et al. 2012) (Fig. 4b). The Mo6+ cation is simultaneously reduced to Mo5+ in PMo12 to form molybdenum blue via electron transfer(Dolbecq et al. 2010), with the concomitant solution color change to blue. Fortunately, the structure of PMo12 is not destroyed (Chen et al. 2019; Glass et al. 2016; He and Yao 2006). Due to the oxidative property of PMo12, a number of degradation products can be further oxidized to compounds such as 5-HMF, formic acid, and levulinic acid. PMo12 regeneration properties The long-term cycle stability of a catalyst is an important index to evaluate its performance, especially in industrial application. Therefore, the recovery rate of PMo12 after three cycles and its in uence on the TRS yield were investigated. The absorbance of PMo12 at 700 nm was used to determine the reduction degree because both variables have a linear relationship (Fig. 5a). The absorbance curve of PMo12 in a wavelength range from 400 to 900 nm under different hydrothermal reaction times is shown in Fig. 5b. Upon increasing the reaction time from 60 min to 240 min, the reduction degree of PMo12 also increased, which indicates that WS was degraded. The reduction degree of molybdenum blue (reductive PMo12) decreased gradually in the process of electrooxidation, being gradually oxidized and converted to oxidative PMo12 (Fig. 5c)(Yang et al. 2019). Fig. 5d demonstrates that the TRS yield changed between the rst and third cycle of PMo12 treatment, decreasing from 69.56 wt% for the rst cycle to 58.32 wt% for the third cycle. Nevertheless, the recovery rate of PMo12 after the third cycle was still 80.76% of the initial value. The decreased catalytic performance of recovered PMo12 may be due to organics adsorption by PMo12, which affects the oxidative degradation of WS. Fortunately, a good level of PMo12 recycling performance was still maintained. The color change of PMo12 solution during the redox process is illustrated in Fig. 6. Under the hydrothermal reaction, the WS–PMo12 mixture changed from yellow to dark blue (Fig. 6a and Fig. 6b), indicating the reduction of PMo12 to molybdenum blue. The Mo6+ cation in PMo12 is reduced by electrons from WS, and the reduction degree of PMo12 increases. The reduction degree of a POM is de ned as the average number of electrons (in moles) that are transferred from the biomass to one mole of the POM anion(Liu et al. 2016; Zhao et al. 2020). A CHI660E electrochemical workstation was utilized to oxidize a molybdenum blue solution at a constant voltage of 1.0 V in the electrolysis, which was lower than the standard potential of water electrolysis (1.23 V)(Weng and Chen 2015). During electrolysis, Mo5+ in molybdenum blue was oxidized to Mo6+ at the anode. Simultaneously, the molybdenum blue was converted to oxidative PMo12. The color of the solution turned back to yellow, and WS was oxidized and degraded (Fig. 6c). A H+ from WS was transferred to the cathode, generating hydrogen. Page 8/16

Co onclusions A large amount of dissolved WS pollutants are accumulated in pulping wastewater during the process of repulping and reuse of OCC waste paper. To solve this problem, we investigated the degradation of WS by the green catalytic oxidant PMo12, and the mechanism of the reaction was explored. WS was effectively oxidized and degraded to high value-added RS. During the hydrothermal reaction, at 145 °C, a PMo12 dosage of 30 wt%, and a reaction time of 120 min, the TRS yield from WS reached 73.54 wt% and glycolic acid (11.05 wt%), which was equivalent to 84.59 wt% of starch recovered from OCC pulping wastewater. Molybdenum blue can be oxidized to oxidative PMo12 by electrolysis, realizing the recycle and reuse of PMo12. The present study on the oxidative degradation of starch by PMo12 has theoretical signi cance and potential application value for resource utilization of WS in OCC pulping process and cleaner management of OCC waste paper.

Declarations Acknowle edgements The author thanks the support from the National Natural Science Foundation of China (No.3177030417) and the Major Science and Technology Plan Project of Jiangsu Province (BE2018129). The authors also thank Zhina Lian (Nanjing Forestry University) for the HPLC tests, and Rui Liu (Nanjing IPE Institute of Green Manufacturing Industry) for the linguistic assistance. Author Contributions Yongzhen Qiao: Conceptualization, Formal analysis, Methodology, Validation, Investigation, Writing - Original Draft, Writing - Review & Editing. Weisheng Yang: Investigation, Methodology, Formal analysis. Xiu Wang: Language. Liang Jiao: Resources. Huiyang Bian: Language, Resources. Yiqin Yang: Methodology, Resources. Shumei Wang: Resources. Hongqi Dai: Conceptualization, Supervision, Funding acquisition. Availa abiliity of data and materials s Availability of data and materials has been provided. Ethics approval and consent to participate Not applicable. Co onsent for publication Not applicable. Co ompeting interests The authors declare that they have no competing interests.

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31. Sun L, Wan S, Yu Z, Wang Y, Wang S (2011) Anaerobic biological treatment of high strength cassava starch wastewater in a new type up- ow multistage anaerobic reactor. Bioresour Technol 104:280288 doi:10.1016/j.biortech.2011.11.070 32. Tian J, Wang J, Zhao S, Jiang C, Zhang X, Wang X (2010) Hydrolysis of cellulose by the heteropoly acid H3PW12O40. Cellulose 17:587-594 doi:10.1007/s10570-009-9391-0 33. Wang C GH, Chen X, Ni S, Liu N, Dai H (2020) Study on the Preparation and Application Performance of Nano Starch. Journal of Qilu University of Technology 34:28-34 doi:10.16442/j.cnki.qlgydxxb.2020.04.005 34. Wang S-S, Yang G-Y (2015) Recent Advances in Polyoxometalate-Catalyzed Reactions. Chemical reviews 115:4893-4962 doi:10.1021/cr500390v 35. Weng S, Chen X (2015) A hybrid electrolyzer splits water at 0.8 V at room temperature. Nano Energy 19:138-144 doi:10.1016/j.nanoen.2015.11.018 3 . Wu W, Liu W, Mu W, Deng Y (2016) Polyoxymetalate liquid-catalyzed polyol fuel cell and the related photoelectrochemical reaction mechanism study. J Power Sources 318:86-92 doi:10.1016/j.jpowsour.2016.03.074 37. Yang W, Du X, Liu W, Tricker AW, Dai H, Deng Y (2019) Highly E cient Lignin Depolymerization via Effective Inhibition of Condensation during Polyoxometalate-Mediated Oxidation. Energy Fuels 33:6483-6490 doi:10.1021/acs.energyfuels.9b01175 3 . Yu IKM, Tsang D, Yip A, Chen S, Wang L, Ok YS, Poon CS (2017) Catalytic Valorization of Starch-Rich Food Waste into Hydroxymethylfurfural (HMF): Controlling Relative Kinetics for High Productivity. Bioresour Technol 237:222-230 doi:10.1016/j.biortech.2017.01.017 39. Zhang J, Liu X, Sun M, Ma X, Han Y (2012) Direct Conversion of Cellulose to Glycolic Acid with a Phosphomolybdic Acid Catalyst in a Water Medium. ACS Catalysis 2:1698-1702 doi:10.1021/cs300342k 40. Zhao Y, Wang T, Wang H, Lu S, Wang Y, Zhao M, Lu X, Li B (2020) Study on POM assisted electrolysis for hydyrogen and ammonia production. Int J Hydrogen Energy doi:10.1016/j.ijhydene.2020.07.147 41. Zhu H, Qin L, Hu Y, Wei D, Hai Z, Li A, Xie X, Han C (2017) Occurrence and transformations of carbon, nitrogen, and phosphorus related to particle size fraction of sweet potato starch wastewater during hydrolytic acidi cation processes. Environ Sci Pollut Res 24:20717-20724 doi:10.1007/s11356-0179724-8

Figures

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Figure 1 Schematic diagram of the oxidative degradation of the WS using PMo12 and electro-oxidation cycle of PMo12.

Figure 2 Structure of the electrolysis cell.

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Figure 3 a Glucose standard curve; The in uence of b Reaction temperature; c Dosage of PMo12; d Reaction time on hydrothermal oxidation.

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Figure 4 The proposed reaction pathway in the degradation of WS with PMo12

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Figure 5 Cyclic performance test of PMo12 with a Calibration curve for PMo12 solution with different reduction degrees; b UV-Vis spectrum of WS-PMo12 solution during the hydrothermal degradation process (diluted to 1 mmol/L); c UV-Vis spectrum of PMo12 solution during electro-oxidation (diluted to 1 mmol/L); d Relationship between recycling recovery of PMo12, TRS yield and cycle times.

Figure 6 The color change of PMo12 at redox process: a WS-PMo12 solution before heating; b WS-PMo12 solution after heating; c PMo12 solution after electrolysis.

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PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

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Utilization of bio-polymeric additives for a sustainable production strategy in pulp and paper manufacturing: A comprehensive review SOUMYA BASU, SHUANK MALIK, GYANESH JOSHI, P.K. GUPTA & VIKAS RANA. Renewable and bio-based materials have gained great interest on an industrial scale owing to environmental issues. Paper industries also are constantly exploring bio-resources for intrinsic chemico-physical property enhancement of paper and paper products. These bio-resources will potentially increase their cyclability besides making paper compatible beyond traditional uses. Mechanical beating or use of chemical additives or the combination of these methods are widely used to improve critical paper characteristics such as strength, surface smoothness, density, brightness, filler retention, water and grease resistivity etc. These chemical additives as mill effluents are hazardous and have detrimental effect on environment. So, to move ahead of traditional practices, the present review discusses about the production and utility of abundantly available renewable bio-polymers and their products such as starch, cellulose, plant-based proteins, microbial biopolymers, animal-based biopolymers, and natural gums etc. They represent ample prospect in terms of research and development on their functionality and industrial applications. Contact information: Cellulose & Paper Discipline, Forest Products Division, Forest Research Institute, Dehradun-248006, Uttarakhand, India. Carbohydrate Polymer Technologies and Applications, Vol.2, 25 December 2021, 100050.

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Article 9 – Bio-polymeric Additives

Carbohydrate Polymer Technologies and Applications 2 (2021) 100050

Contents lists available at ScienceDirect

Carbohydrate Polymer Technologies and Applications journal homepage: www.elsevier.com/locate/carpta

Utilization of bio-polymeric additives for a sustainable production strategy in pulp and paper manufacturing: A comprehensive review Soumya Basu, Shuank Malik, Gyanesh Joshi, P.K. Gupta, Vikas Rana∗ Cellulose & Paper Discipline, Forest Products Division, Forest Research Institute, Dehradun-248006, Uttarakhand, India

a r t i c l e

i n f o

Keywords: Cellulose and derivatives Hemicelluloses Starch and derivatives Bio-polymeric additive Pulp and paper manufacturing Paper industries

a b s t r a c t Renewable and bio-based materials have gained great interest on an industrial scale owing to environmental issues. Paper industries also are constantly exploring bio-resources for intrinsic chemico-physical property enhancement of paper and paper products. These bio-resources will potentially increase their cyclability besides making paper compatible beyond traditional uses. Mechanical beating or use of chemical additives or the combination of these methods are widely used to improve critical paper characteristics such as strength, surface smoothness, density, brightness, filler retention, water and grease resistivity etc. These chemical additives as mill effluents are hazardous and have detrimental effect on environment. So, to move ahead of traditional practices, the present review discusses about the production and utility of abundantly available renewable bio-polymers and their products such as starch, cellulose, plant-based proteins, microbial biopolymers, animal-based biopolymers, and natural gums etc. They represent ample prospect in terms of research and development on their functionality and industrial applications.

1. Introduction The key to sustainable chemical processes on an industrial scale requires the development of eco-friendly products from renewable resources (Beard, Ledward & Sergeeva, 2017). In an era of plastic menace followed by a ban of plastic based handy materials in many countries (European commission, 2011; Jambeck et al., 2015; Rochman et al., 2013), paper serves to be an excellent alternative medium that can be extensively used in various applications ranging from printing/writing, packaging, household products, micro-fluidic devices and so on. Paper is lightweight, biodegradable, mechanically stable and a recyclable commodity (Rastogi & Samyn, 2015). Researchers are involved in the development of various kind of products by zero chemical use and discharge for the maintenace of enviornment sustainability (Gupta, Joshi, Rana, Rawat & Sharma, 2020). It can be produced from woody or nonwoody biomass or recycled fibres through chemical and/or mechanical pulping. The chemical pulping processes solubilise lignin fraction from the cellulose matrix, followed by the conversion of the later into paper sheets (Shen, Fatehi & Ni, 2014). Lignin solubilization is a desirable process in paper manufacturing but loss of hemicelluloses due to peeling action of alkali and their leaching with black liquor is an unwanted phenomenon which directly impacts on pulp yield and responsible for poor strength properties in final paper sheet due to low content of hemicelluloses (Bi et al., 2021; Gulsoy & Eroglu, 2011; Malik, Rana, Joshi,

∗

Gupta & Sharma, 2020). To overcome this loss of hemicelluloses, additive pulping has been established as a tool to target high pulp yield with enhanced recovery of hemicelluloses. The commonly used pulping additives are sodium borohydride (NaBH4 ), hydrogen sulphide (H2 S) gas, polysulphide (PS) and anthraquinone (AQ) (Ban & Lucia, 2003; Gulsoy & Eroglu, 2011; Hart & Rudie, 2014; Istek & Gonteki, 2009; Olm & Tormund, 2000). Applications of one or more of these yield increasing agents are capable to stabilize the reducing ends in hemicellulosic structure, and leads to check in peeling reactions. Amongst these additives, AQ has been explored extensively due to its low cost, high efficiency towards increased pulp production and environmental protection. Further, its application for different types of lignocellulosic raw materials, categorized it separately from other pulping additives. Recently AQ has been successfully explored for pulping of different type of raw materials such as agricultural waste or residues (Ferrer, Vargas, Jameel & Rojas, 2015; Hedjazi, Kordsachia, Latibari & Tschirner, 2009; Omer, Khider, Elzaki, Mohieldin & Shomeina, 2019; Potůček, Gurung & Hájková, 2014), woods (Erisir, Gumuskaya, Kirci & Misir, 2015; Francis, Bolton, Abdoulmoumine, Lavrykova & Bose, 2008; Venica, Chen & Gratzl, 2008) and bamboos (DENiZ, Okan, Serdar & Şahin, 2017; Jahan, Sarkar & Rahman, 2015; Kamthai, 2007; Nurul, Suhaimi & Rushdan, 2015) etc. Although paper sheets from virgin (raw) biomass is superior in terms of physical properties as compared to recycled fibres, the later has

Corresponding author. E-mail addresses: ranav@icfre.org, vikasranaji@gmail.com (V. Rana).

https://doi.org/10.1016/j.carpta.2021.100050 Received 19 July 2020; Received in revised form 19 February 2021; Accepted 19 February 2021 2666-8939/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

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Carbohydrate Polymer Technologies and Applications 2 (2021) 100050

Table 1 Common bio-additives used for diﬀerent grade for papers. Bio-additive

Type of Pulp/ Paper

Reference

Cationic cellulose

Carboxymethyl cellulose

- Bleached softwood kraft pulp - Recycled cardboard boxes pulp

Strand et al., 2017; Tarrés et al., 2018

Cellulose nanoﬁbers

Tarrés et al., 2018; Delgado Aguilar et al., 2015; Espinosa et al., 2015; Jin, Tang, Liu, Wang & Ye, 2021

Cationic starch

- Bleached softwood pulp with pine/spruce ratio 70:30 - Bleached softwood kraft pulp - Bleached bagasse soda pulp

Ulbrich et al., 2012; Strand et al., 2017; Hamzeh, Ashori, Khorasani, Abdulkhani & Abyaz, 2013

Hemicelluloses

- Sulphate kraft pulp - Eucalyptus kraft pulp

Lima et al., 2003

Chitosan

- Bleached bagasse soda pulp - Old corrugated containers (OCC) recycled pulp

Hamzeh et al., 2013; Bhardwaj et al., 2016

Carrageenan

- Bleached pinewood kraft pulp

Liu et al., 2017

Proteins (soy, cottonseed)

- OCC, Neutral sulphite semichemical pulp (NSSC), Virgin kraft pulp - Whatman paper, speciality paper

Salam et al., 2015; Cheng et al., 2017

Guar gum

- Tissue Paper

Dasgupta, 1999

Bleached chemithermo-mechanical pulp (BCTMP) Recycled pulp Unbleached wheat straw soda pulp Unbleached bagasse soda pulp

Recycled cardboard boxes pulp Bleached kraft hardwood pulp (BKHP) Semichemical wheat straw pulp Food packaging paper

been in focus owing to environmental intendancy measures. The loss in strength properties by recycling of fibre is ascribed to its repetitive drying phase, which results in irreversible hornification of the fibres. Since, the hornified fibres fail to achieve their actual configuration comparable to its virgin state, the inter-fibre bonding (interaction of functional bonding groups like carboxyl, hydroxyl and carbonyl) is largely affected (Fernandes Diniz, Gil & Castro, 2004; Hubbe, Venditti & Rojas, 2007; Minor & Atalla, 1992; Nazhad & Sodtivarakul, 2004). A number of chemicals are used in the manufacturing of paper sheets and paper-based products to abridge these gaps in recycled fibres and also enhance the performances of virgin fibres. These chemical additives are employed to engineer conventional paper properties like strength, printability, opacity and brightness. Besides these features, additives can confer special attributes to paper based cellulosic fibres such as gas barrier, magnetic properties, superhydrophobicity, flame retardancy, electrical conductivity, photocatalytic activity etc. (Arbatan, Zhang, Fang & Shen, 2012; Lahtinen, Nättine & Vartiainen, 2009; Shen, Song, Qian & Ni, 2011). However, paper mill effluents comprise of these chemical additives and happen to be detrimental to living forms since they can disturb the overall systemic behaviour in species. Moreover, such effluents often result in oxygen depletion of water bodies and the aquatic organisms are posed with alarming threats of anoxia (Bijan & Mohseni, 2004; Kim Oanh et al., 1999; Lacorte et al., 2003; Thacker, Nitnaware, Das & Devotta, 2007). Hence, more sustainable additives can be selected on the basis of relevant criteria including low toxicity, compatibility with the host material, retention capability and expense. The application of bio-polymers has been a successful method to minimize the risk of environmental abasement and enhance the strength properties of cellulosic fibre networks in paper production (Fatehi, Qian, Kititerakun, Rirksomboon & Xiao, 2009). Natural polymers like starch (cationic, anionic, oxidized starch etc.) (Johansson, Lundström, Norgren & Wågberg, 2009; Lindström, Fellers, Ankerfors & Nordmark, 2016; Shen et al., 2014), gums (Lee, Lee & Youn, 2005; Lima, Oliveira & Buckeridge, 2003), car-

Gao et al., 2016; Rana et al., 2021

rageenan (Liu, Li & Xie, 2017), soy protein (Salam, Lucia & Jameel, 2015), crop grain based gluten (Andersson, 2008; Guazzotti, Marti, Piergiovanni & Limbo, 2014), molasses (Fahmy, 2014), cellulose derivatives (Fatehi et al., 2009; Lindström et al., 2016; Shen et al., 2014), chitosans (Balan, Guezennec, Nicu, Ciolacu & Bobu, 2015), alginates (Andersson, 2008) etc. serve as additives in paper production to address diverse functions starting from strength addition to coating, sizing agents to retention aids (Andersson, 2008; Ren, Peng, Peng & Sun, 2011; Zakrajšek & Golob, 2009). Table 1 represents the application of some common bio additives for their use in diffeent type of pulp and paper manufacturing. Nature of charge on the biopolymers or their derivatives further influence the interactive behaviour with negatively charged paper furnish. Anionic biopolymers do not readily interact in bonding as the paper furnish is itself anionic in nature. Anionic biopolymer requires an additional cationic unit such as alum which act as an intermediate for their ability to enhance fibre bonding. In case of anionic biopolymer, the concentration of alum and pH (4.2–4.7) of the system plays a vital role in retention and adsorption of the biopolymer. The use of cationic and anionic biopolymer together provides flexibility in use of anionic biopolymers as the need of alum is eliminated in this case. The anionic biopolymer should be added first followed by the cationic biopolymer in the system for avoiding the system shear. Photographic grade paper is one such example of combination of anionic and cationic polymer (Gao, Li, Shi & Cha, 2016; Read, 1983). The surface charge density of a biopolymer could reverse after cationic or anionic modification. The surface charge density of cationic modified cellulose increases in comparison to unmodified cellulose fibres. However, it was much greater in case of cationic starch. The addition of cationic modified biopolymer could decrease the zeta potential because of existing positive charge. On the other hand, the zeta potential of pulp suspension increases on addition of anionic modified biopolymer (Gao et al., 2016; Read, 1983).

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Our research team have been dedicatedly working in the ﬁeld of carbohydrate chemistry as well as functional modiﬁcation of cellulose to promote sustainable and environment friendly measures in pulp and paper technology (Gupta et al., 2020; Joshi et al., 2019, 2015; Joshi, Naithani, Varshney, Bisht & Rana, 2017; Rana, Das, Gogoi & Kumar, 2014; Rana, Malik, Joshi, Rajput, & Gupta, 2021). The purpose of the present review is to bring together and explicitly discuss the production, functional-chemistry and applications of bio-based polymers as substitutes of harmful chemical additives and depleting fossil based chemicals (Shen et al., 2014) used in pulp and paper industries. This review mainly covers the topic for the duration of last two and half decades i.e., studies carried out from 1995 to 2020.

tion parameters with varying raw material, due to their difference in fibre morphology and chemical makeup (Gao et al., 2016). Although many processes have been reported regarding the production of cationic cellulose, alkalization-cationization dual step conversion has been the most effective one (Moral, Aguado, Ballesteros & Tijero, 2015). Alpha cellulose extracted from a cellulosic biomass can be etherified with 2‑hydroxy-3-trimethyl ammonium propyl group by the reagent 2,3-epoxypropyltrimethyl ammonium chloride (EPTAC). Since this chemical is toxic and highly unstable, alternatively 3‑chloro-2hydroxypropyltrimethyl ammonium chloride (CHPTAC) can be used. The cationization process is preceded by an essential alkali mediated charging procedure of the hydroxyl groups of cellulose (Fig. 1) (Khalil, Beliakova & Aly, 2001; Liu, Ni, Fatehi & Saeed, 2011; Rana et al., 2021; Su et al., 2016). The degree of substitution of quaternary ammonium group on the cationic cellulose can be confirmed by determination of nitrogen content before and after modification (Moral et al., 2015). Since the cationic modification of cellulose makes its surface positively charged, the same when used as an additive while paper making results in high filler retention, surface homogeneity, improved drainage property, improved absorption of anionic fines and strength enhancement (Halab-Kessira& Ricard, 1999; Montplaisir, Chabot & Daneault, 2006; Sain & Boucher, 2002; W. Xie, Feng & Qian, 2008). Gao et al. (2016) have specifically emphasized on the production and utilization of cationized cellulose fibrils (CCF). CCF additive has comparable influence of paper strength enhancement (2–3% tensile index improved) as done by popular cationic starch (CS) additive. Tensile index is the maximum force per unit width developed in a paper specimen before rupture under prescribed conditions divided by grammage (gsm) of paper. The authors also found that CCF confers slightly improved (∼12%) tear strength in paper than CS at low (2–4%) concentrations. Hence cationic cellulose can be considered as a promising alternative of conventional synthetic cationic poly-electrolytes used for paper strength enhancement.

2. Cellulose and derivatives Cellulose is the most abundant polysaccharide available in nature as a primary structural constituent of plant cell wall composed of 𝛽(1–4) linked d-glucose units (Fig. 1). Apart from plants, cellulose is also found in bacteria from various genera like Aerobacter, Agrobacterium, Gluconacetobacter, Acetobacter, Azotobacter, Achromobacter, Escherichia, Sarcina, Salmonella and Rhizobium. Since cellulose is mechanically strong, renewable and biodegradable, it has been in focus for diverse small to large scale applications (Rangaswamy, Vanitha & Hungund, 2015). Cellulose is the backbone of pulp and paper products. To further broaden its application domain, the multiple hydroxyl groups of the cellulose can be modified with chemical agents. Typically, cellulose derivatives are resultants of esterification and/or etherification of hydroxyl groups of cellulose. Apart from these, nano-cellulose has gained attention as an application tool in material science innovations as well as biomedical applications in recent times (Gao et al., 2016; Lahtinen et al., 2014; Shaghaleh, Xu & Wang, 2018). The chemical and physical properties of cellulose derivatives depend upon the type of substituting group, the degree of substitution (DS), the uniformity of substitution and the length of the cellulose molecules. In practice, it is very difficult to completely replace all the hydroxyl groups present in cellulose by other functional groups due to steric factors. The steric crowding may inhibit complete reaction. Accessibility, another factor may restrict the complete replacement of hydroxyl groups. Since the reactions are conducted under heterogeneous reaction environment, not all the hydroxyl groups may be accessible to the reaction, principally those in the crystalline regions. In overall, not all the accessible hydroxyl groups are equally reactive. The three hydroxyl groups of glucose units differ in their reactivity and the relative rates are not necessarily the same for other reagents. Most of the commercial cellulose derivatives are the products of only partial reaction, i.e. they contain a definite proportion of unsubstituted hydroxyl groups. The physical and chemical properties of cellulose derivatives are strongly affected by the DS and the degree of polymerization (DP). Properties that are mostly influenced by fluctuating the DS are the solubility, swelling and plasticity. Derivatives of low DS are more sensitive to water. Derivatives having high DS with nonpolar substituents, the water solubility is decreased, the sorption of water is decreased, and the solubility in organic solvents is increased. On the other hand, the plasticity is increased by the substitution of nonpolar groups. If the mechanical properties are important in the final end product, a balance must be struck between a low DP, which will confer ease of fabrication, and the somewhat higher DP crucially required for adequate mechanical properties (Mcginnis & Shafizadeh, 1979). Some common derivatives of cellulose and their route of synthesis are presented in Fig. 1 (Abdel-Halim, 2014; De Carvalho Oliveira et al., 2010; Joshi et al., 2015, 2019; Rana et al., 2021).

2.2. Carboxymethyl cellulose (CMC) There has been rigorous research and commercial applications when it comes to carboxymethyl cellulose. It is a versatile cellulosic product that can be synthesized from plant based biomass and/or recycled fibres and finds its use beyond traditional paper science (Fatehi, Kititerakun, Ni & Xiao, 2010; Joshi et al., 2015). CMC is an anionic polymer with high surface charge (negative) that has been identified as a potential strength enhancer in papermaking. Its absorption onto fibres enhances under acidic conditions (Jokinen, Niinimäki & Ämmälä, 2006; Watanabe, Gondo & Kitao, 2004). The synthesis of carboxymethyl cellulose (Fig. 1) proceeds in the same manner as that of cationic cellulose i.e. alkali mediated activation of hydroxyl group followed by etherification (carboxymethylation) [Williamson’s ether synthesis followed by carboxymethylation in SN 2 mechanism]. The commonly used carboxymethylating agent is sodium monocloroacetate under optimized conditions of temperature, time and chemical concentration depending upon raw material type (Joshi et al., 2015; Tijsen, Kolk, Stamhuis & Beenackers, 2001; Varshney & Naithani, 2011; Varshney et al., 2006). In a general context, carboxymethyl cellulose improves the hydrophobicity of paper based (cellulosic) products, enhances surface strength, improves oil resistance, decreases porosity (increased air resistance) and thickens coating materials (rheology modifications) etc. (Dulany, Batten, Peck & Farley, 2011; Holik, 2006; Shen & Qian, 2012; Tang, Zhou, Zhang & Zhu, 2013). Delving deeper into the properties of CMC, the work of Taggart, Schuster and Schellhamer (1991) offers a clear picture of CMC when used alongside conventional starch derivatives. CMC (with DS∼ 1.4 M/AGU) in an aqueous solution (0.1–5%) has been specifically utilized as a retention aid and strength enhancer alongwith cationic starch onto a paper furnish. Interestingly, the adsorption of starch increases by ∼60% when added in combination to CMC and by ∼30% when CMC is added after

2.1. Cationic cellulose Standardized procedures have been devised for the production of cationic cellulose; however, the same requires unique optimiza3

S. Basu, S. Malik, G. Joshi et al.

Carbohydrate Polymer Technologies and Applications 2 (2021) 100050

Fig. 1. Preparation routes for diﬀerent cellulosic products used in paper making .

starch (starch:CMC=10:1). However, separate addition (starch followed by CMC) was found to be most effective in enhancing the Mullen index by ∼35%, tensile index by ∼23% and filler retention by ∼50%. The work establishes the properties of CMC as strength additive and retention aid by utilizing different commercial starch and CMC varieties as well as different pulp types e.g. virgin chemical pulp, mixed pulp, recycled pulp etc. with consistent results.

kali cellulose formation (by treating with sodium hydroxide under controlled physico-chemical conditions) followed by a reaction with gaseous ethylene oxide. This reaction results in a series of etheriﬁcation of the hydroxyl groups by converting the same into hydroxyethyl groups. This makes the overall molecule water soluble. Hydroxyethylation can also be done in a single step by a treatment of cellulose with high ethylene oxide concentration (200% w/w of cellulose) in presence of higher alkali charge (>20%) at a considerably high temperature (100 °C) and often under high pressure. Hydroxyethyl cellulose has superlative capabilities as thickening, binding, emulsifying, and dispersing agent. It has superior water retention capabilities hence producing solutions of varying viscosities. For these properties, it has been utilized in paper industry as a surface sizing and pigment coating agent. Hydroxyethyl cellulose (at a concentration 0.5–2%) has also been found to have

2.3. Hydroxyethyl cellulose Hydroxyethyl cellulose is another attractive cellulose derivative which is water soluble and non-ionic. It is prepared from bleached/deligniﬁed cellulosic substrate by a two step process (Fig. 1). Industrial production of hydroxyethyl cellulose comprises of active al4

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Carbohydrate Polymer Technologies and Applications 2 (2021) 100050

enhanced the dry tear strength of paper by 14% in bleached wood pulp (Abdel-Halim, 2014; Bülichen, Kainz & Plank, 2012; Miura, Nishizawa, Nishimura & Sekigawa, 1972; Tang et al., 2013).

tensile index of paper made from Eucalyptus bleached pulp. The tensile index of the handmade paper from same pulp has been enhanced by ∼11% with the action of NCC. The application of NCC ranges from pulp and paper industries to pharmaceuticals and from food to cosmetics (Bai, Holbery & Li, 2009; De Jesus Silva, De Almeida, De Oliveira, Da Silva & De Mendonça Neto, 2013; Ditzel et al., 2017; Liu, Chen, Yue, Chen & Wu, 2011; Peng, Dhar, Liu & Tam, 2011).

2.4. Nanocellulose The latest and the most acclaimed area of applied cellulosic science is the production and application of nanocellulose (Hubbe, 2019; Raghav, Sharma & Kennedy, 2021). There are primarily two types of nanocellulose:

2.5. Other cellulose derivatives Methyl cellulose is another important water-soluble cellulose derivative produced by alkaline activation of cellulose under heat treatment followed by a reaction with methyl sulphate or methyl chloride (Fig. 1). It works as adhesives, thickeners, binders, emulsiﬁers and stabilizers. Methyl cellulose is widely used as sizing agents in paper industries (Karrasch, Jäger, Saake, Potthast & Rosenau, 2009; Lavanya, Kulkarni, Dixit, Raavi & Krishna, 2011). Another derivative, hydroxypropyl cellulose, is produced commercially by alkali activation followed by reaction with propylene oxide at high temperature (120–160 °C) (Miura et al., 1972) (Fig. 1). Hydroxypropyl cellulose and hydroxypropyl methyl cellulose (HPMC) are used as surface coating and barrier additives. HPMC as coating additive controls water absorption capacity, ﬂexibility and mechanical properties of paper (Khwaldia, 2013; Klass, 2011; Sothornvit, 2009).

(a) Nano-Fibrillated Cellulose (NFC) (b) Nano-Crystalline Cellulose (NCC) NFC or microfibrillated cellulose differs from NCC or cellulose nanocrystals in the process of manufacturing; the former is produced from mechanical shearing whereas the latter is manufactured purely by chemical hydrolysis (Arbatan et al., 2012; Aulin, Lindström & Strom, 2013; Lavoine, Desloges, Dufresne & Bras, 2012; Martins et al., 2012; Mertaniemi, Laukkanen, Teirfolk, Ikkala & Ras, 2012; Pajari, Rautkoski & Moilanen, 2012; Syverud & Stenius, 2009). The disintegration process for obtaining NFC from cellulosic raw material differs with nature of raw material. Enzymatic and chemical pre-treatment methods of cellulosic mass or delignified pulp prior to mechanical homogenization have also been reported. This process predominantly yields homogeneous fibrils of width ranging between 3 and 20 nm. Since, the composition of fibres is conserved; the fibrils have anionic surface charge. This negative charge is conferred by carboxyl groups of hemicellulosic origin (Ahola, Österberg & Laine, 2008). This surface to charge ratio is the most important property of NFC that imparts mechanical strength (both wet and dry) to paper sheets (Ahola et al., 2008; Nakagaito, Iwamoto & Yano, 2005; Pääkkö et al., 2008; Saito, Nishiyama, Putaux, Vignon & Isogai, 2006). The adsorption and activity of cationic poly-electrolytes (in very low concentrations) have improved in a bi-layer system by the addition of nano-fibrillated cellulose due to increment of bonding sites provided by NFC. The wet and dry tensile strength has increased upto ∼40% by the addition of NFC. The same also indicates that NFC has the potency to replace various chemical strength additives or minimize their concentration used in paper manufacturing (Ahola et al., 2008). Sehaqui et al. (2013) have experimentally established that NFC increases the tensile index and tensile energy absorption (TEA) in unbeaten softwood pulp and the results are comparable to the same achieved by mechanical beating of identical pulp. TEA is the work done when a paper specimen is stressed to rupture in tension under prescribed conditions as measured by the integral of the tensile strength over the range of tensile strain from zero to maximum strain. It is expressed as energy per unit area (test span × width) of paper specimen. The strength indices are found to increase by 20–30% as compared to control due to improved inter-fibre stress transfer offered by NFC. This gives a significant perspective that amalgamates improvement of paper properties alongwith the reduction of energy during the production of high density paper sheets (Sehaqui, 2013; Sehaqui et al., 2012). The other form of well acclaimed nanocellulose is NCC. It can be produced on a good scale from microcrystalline cellulose obtained from acid hydrolysis of delignified lignocellulosic biomasses. Nanoscale miniaturization is commonly done by sulphate hydrolysis and high-pressure homogenization followed by differential centrifugation. NCC is generally needle shaped with dimensions around 60 × 10 nm. The acidic production of NCC imparts negative charges on its surface (Ditzel, Prestes, Carvalho, Demiate & Pinheiro, 2017). Hence it functions as an excellent binder in paper production besides conferring the same with barrier, magnetic and electronic properties. Another unique feature of NCC is the capability to form chiral nematic (parallel orientated crystal) phase beyond a critical threshold. Anionic nano-crystalline cellulose has shown synergistic effect with cationic starch (charge ratio 1:1) to increase the

3. Hemicelluloses Hemicellulose unlike cellulose is a complex branched polymer comprising pentosans and hexosans found in plant cell walls. Based on origin hemicellulose may be broadly classified in to hardwood hemicellulose (Glucuronoxylans and glucomannan), softwood hemicelluloses (galactoglucomannan, and arabinoglucuronoxylan) and storage hemicellulose (Galactomannans). Glucouranoxylan is composed of 𝛽-d-(1→4) xylose units backbone with acetyl substitution at C-2 or C-3 of the xylose and side chains of 4-O-methylglucuronic acid units whereas glucomannans mainly composed of (1→4) linked 𝛽-d-glucopyranose and 𝛽d-mannopyranose units. Galactoglucomannans consist mainly 𝛽-(1→4) backbone of d-glucose and d-mannose with side chains of galactose moieties. 𝛽-(1→4) linked d- xylopyranose units with (1→2) linked branches of d-glucopyranosyluronic acid is the main feature of arabinoglucuronoxylan with 𝛼-(1→3) linked side chains of l-arabinofuranose (Rowell, Pettersen, Han, Rowell & Tshabalala, 2005). The interaction varies with the degree of galactosylation of the linear xyloglucan backbone (Buckeridge, Dietrich & de Lima, 2000; De Lima & Buckeridge, 2001; Vincken, De Keizer, Beldman & Voragen, 1995). Galactomannans are chief storage hemicelluloses in leguminous seeds having linear 𝛽-(1–4) linked mannose with single galactosyl branch units (Buckeridge, Pessoa dos Santos & Tiné, 2000). Hemicellulose enhances fibrillation in pulp fibres as well as plasticity and surface area thereby conferring increased fibre-fibre bonding and subsequently higher tensile strength in paper sheets. Ascribed to its hydrophilic properties, hemicelluloses increase the swelling of fibres, hence resulting in increased fibre flexibility and bonding conformations (Anjos, Santos & Simoes, 2004). So, hemicelluloses can act as binders while imparting improved tensile and burst indices. However, hemicellulose as additive has been proven to be more effective than in-situ hemicelluloses in terms of strength promotion due to the fact that greater part of in-situ hemicelluloses lie deeper into the cell wall and cannot participate in fibre bonding. Hemicellulose content reduces refining energy of pulp, although higher hemicellulose (∼20%) content has been shown to be detrimental to pulp strength (tear vs. tensile) as compared to lower hemicellulose content when the refining energy is increased (2–5 N/m) (Mobarak & Fahmy, 1973). It has also been found that hemicellulose as wet end additives provide better strength to pulp fibres when added after refining due to enhanced hydrogen bonding between cellulose and hemicellulose (Anjos et al., 2004; Mobarak & Fahmy, 1973). 5

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Lima et al. (2003) have emphatically portrayed the property enhancement of paper-sheets made from Eucalyptus pulp by the action of hemicellulose from different legumes. The article experimentally demonstrated that after addition of hemicellulose, tear and burst indices significantly improved upto a maximum of 30% and 20% respectively. Furthermore, retention of fines enhanced by 3% [Increase in Apparent Specific Weight (ASW in kg/m3 )], tensile index by 11%, TEA by 19% and specific elastic modulus by 3% as compared to control (without added hemicellulose) samples. An interesting fact has been established by Mobarak and Fahmy (1973) in their research on hemicellulose additives. They have shown that the retention of added hemicellulose which was previously extracted from hardwood has lowered (by ∼4%) in hardwood pulp itself with respect to the retention of hemicellulose obtained from straw. Besides, straw pulp has 5% enhanced capacity to retain hemicelluloses than hardwood. Owing to this fact, sheet prepared from straw pulp was more compact than that of hardwood pulp after hemicellulose addition.

sulfonium, phosphonium etc. forms. However, alkaline charging followed by a reaction with 3‑chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) is the most common method for producing cationic starch (Fig. 2). Gelatinized (gelatinization of starch increases the reaction rate) starch in presence of alkali and CHPTAC forms quaternary ammonium cationic starch ether at temperatures around 40 °C with a starch concentration of 25–35% (w/v) (Ghasemian, Ghaffari & Ashori, 2012). Sodium sulphate is often used to maintain the integrity of the unswollen starch granule during the entire reaction period. A reaction efficiency of around 85% and degree of substitution around 0.5 is considered legible for the application of the modified product. Interestingly, amylose and amylopectin have different adsorption potential in pulp fibres and amylose is more potent in getting adsorbed. Although cationic starch shows low Langmuir type isotherms (rate of adsorption as a function of applied pressure), its affinity to fibre-fibre bonding is comparatively higher than other modified starch forms. The adsorption of cationic starch onto fibres depends upon the electrolyte concentration in the system (Ulbrich, Radosta, Kießler & Vorwerg, 2012). The properties conferred by cationic starch can be grouped in four main sections: (i) Enhancement of mechanical strength, (ii) Retention aids to fines and fillers, (iii) Improved drainage, and (iv) Generating low toxic paper-mill effluent. The reactive cationic groups provides strong adsorption interface between fibres, fines and fillers through electrostatic attraction (Carr & Bagby, 1981; Ghasemian et al., 2012; Lee et al., 2002; Pettersson, Höglund & Wågberg, 2007; Solarek, 1986; Ulbrich et al., 2012; Xie, Yu, Liu & Chen, 2006; Yang, Qiu, Qian & Shen, 2013; Zakrajšek, 2008; Zakrajšek & Golob, 2009). Ghasemian et al. (2012) have repored that cationic starch can significantly increase the tear, tensile and burst indices of virgin and mixed pulps. A maximum tensile index of 29.2 Nm/g, tear index of 18.7 mKm2 /g and burst index of 2.74 kPam2 /g was observed in handsheets made from mixed pulps with cationic starch additive. The strength properties have increased by 2–3 folds as compared to untreated pulp. Ulbrich et al. (2012) have statistically established the correlation between cationic starch adsorption onto cellulose fibres and its effect on strength enhancement.

4. Starch and derivatives 4.1. Starch Starch is the widely used additive in paper industry showing diverse array of functional attributes owing to its chemical compatibility, abundance and inexpensiveness. Commercial starches are extracted from grain crops, tubers and legume plants. It is a biopolymer formed by the amalgamation of polymeric glucans viz. amylose and amylopectin linked by glycosidic bonds. Amylose is a linear chain of repetitive glucose units linked by 𝛼−1,4-glucosidic bond, whereas amylopectin is a highly branched macromolecule, which consists of short chains of (1→4)-linked 𝛼-d-glucose with (1→6)-𝛼-linked branches. The crystallinity of starch depends upon the relative content as well the structural orientation of amylose and amylopectin. The high viscosity (because of extensive hydrogen bonding of amylopectin) of native or unmodified starch limits its overall accessibility when used as additives in paper making. This drawback is counteracted by plasticization (using solvents like glycerol, sorbitol etc.) or depolymerisation and/or modification (chemical or enzymatic) or blending with other compounds or combination of ionic starch forms (Tomasik & Zaranyika, 1995). Chemical modification is the most frequently used method of commercial starch derivation into functional products like cationic starch, oxidized starch, hydroxyethyl starch etc. For chemical modification, the substitutable hydroxyl groups of starch are to be taken into account. Hydroxyl group at C6 in starch is primary alcohol whereas C2 & C3 are secondary ones; in the presence of glucose ring portion –CHOH–CHOH- instead of C2 & C3 carbons, starch is a triol, whereas glycosidic bonds at this juncture makes it a hemiacetal. The three hydroxyl groups in glucose subunit make starch susceptible to a number of possible modifications. The basic chemical modification of starch is usually done via oxidation, esterification and etherification. Unmodified starch as an additive has been proved to have conferred mechanical strength (to some extent), surface smoothness and optical property to paper (Bajpai, 1999; Hermansson & Svegmark, 1996; Jane, 1995; Larotonda, Matsui, Sobral & Laurindo, 2005; Matsui et al., 2004; Perry & Donald, 2000; Santayanon & Wootthikanokkhan, 2003; Tomasik & Zaranyika, 1995; Vásconez, Flores, Campos, Alvarado & Gerschenson, 2009). Preparation route and structure of some important starch derivatives are presented in Fig. 2 (Colussi et al., 2015; Fu, Zhang, Ren & BeMiller, 2019; Nasir, Abdulmalek & Zainuddin, 2020; Yi, Zhang & Ju, 2014).

4.3. Oxidized starch Oxidative modification of starch is another popular modification procedure employed to make highly viscous native starch to be industrially compatible. The primary and secondary alcohol groups are oxidized under controlled set of conditions to substitute hydroxyl groups with reactive aldehyde and/or carboxyl groups. The modification agents are chosen on the basis of origin and final utilization of the product. Commercially produced oxidized starch are modified at 25–30 °C with low oxidant concentrations (<3%) in controlled batch processes (in presence of oxygen and/or transition metal ion catalysts). Although the most common oxidant used is sodium hypochlorite (Fig. 2), other chemicals such as permanganates, hydrogen peroxide, periodates, persulphates, dichromates etc. were also practiced in recent past (Jonhed, 2006). The carbonyl or carboxylic groups present in anionic (oxidized) starch prevents retrogradation of starch and hence generates a stable modified product that can exert its function under high temperature (cooking) systems besides lowering gelatinizing temperature of starch itself (Vanier, El Halal, Dias & da Rosa Zavareze, 2017). Ascribed to this property, oxidized starch is popularly used as a coating material in paper industry since it prevents clustering of pigments in coating formulations (Jonhed, 2006; Lee et al., 2002; Lewicka, Siemion & Kurcok, 2015; Shen et al., 2014; Vanier et al., 2017; Xie et al., 2006).

4.2. Cationic starch 4.4. Other starch-derived additives Cationic starch is the most popular starch derivative in paper industry imparting useful properties to various kinds of pulp for quality enhancement. It is commercially produced in amino, ammonium,

Acetylated starch is another popular starch derivative of commercial value in paper and food industries. It is produced commercially by alkali 6

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Fig. 2. Diﬀerent starch products as paper additives.

activation followed by acetylation with reagents like acetic acid or acetic anhydride or ketene or vinyl acetate or a combination of all (Fig. 2). Acetylation of starch prevents its retrogradation, reduces enthalpy or ∆H (which depicts the alteration of amylopectin helices) and subsequently reduces crystallinity (improves reactivity). These properties invoke acetylated starch to be an excellent surface sizing agent in paper industry (Ayucitra, 2012; Bello-Pérez, Agama-Acevedo, Zamudio-Flores, Mendez-Montealvo & Rodriguez-Ambriz, 2010; Chen, Kaur & Singh, 2017; Halal et al., 2015; Khalil, Hashem & Hebeish, 1995; Rutenberg & Solarek, 1984). Hydroxypropyl starch, another starch derivative used

for paper coating and surface engineering, is commercially produced in presence of alkali and propylene oxide. Hydroxypropylation again reduces gelatinization temperature, increases swelling power, solubility and improved freeze-thaw stability of starch (Jonhed, 2006; Kaur, Singh & Singh, 2004; Rastogi & Samyn, 2015). 5. Chitosan Chitosan is a deacetylated derivative of chitin (Fig. 3), which happens to be the second most abundant polymer after cellulose in na7

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Fig. 3. Structure of chitosan and its cyanoethyl derivative.

ture found in the exoskeletons of crustaceans, molluscs, insects and also fungi. The main commercial sources of chitin are shrimp and crab shells. Chitosan can be obtained by enzymatic deacetylation of chitin or treatment of the later with NaOH at high temperature. The chemical backbone of chitin unlike cellulose consists of linear chains of complex glycan 𝛽-(1–4)−2-acetamido-2-deoxy-d-glucopyranose, from which chitosan has been derived to possess amine instead of acetamide group. Chitosan unlike its parent molecule has greater solubility due to this substitution (Cissé, Montet, Tapia, Loiseau & Ducamp-Collin, 2012; Puvvada, Vankayalapati & Sukhavasi, 2012; Rinaudo, 2006). Commercially used chitosans are low (50–150 kDa) and medium (700–1000 kDa) molecular weight varieties. Chitosan has been successfully explored to have influenced mechanical, hydrophilic, retention and barrier properties when used at low concentrations (1–2%) (Fernandes et al., 2010). When used in surface engineering, ‘low molecular weight-low concentration’ (LMW-LC) chitosan has been found to reduce water adsorption by ∼20% (increase water barrier properties) in paper than ‘medium molecular weight-higher concentrations’ (MMWHC). This fact can be positively correlated with identical studies resulting in reduction of Cobb-60 Index (water absorption capacity) by 80– 90% and reduction in water vapour transmission rate (WVTR). The same has also been found to lower the hardness and roughness by ∼50% (with and without fillers) of papers, hence proving to be an excellent surface sizing agent. LMW-LC enhances the dry strength of paper (dry strength is inversely proportional to the concentration of LMW chitosan) which is established by a considerable increase in tensile index (reported to be ∼10%) and burst index (reported to be ∼10%) (Habibie, Hamzah, Anggaravidya & Kalembang, 2016). Electron-micrographs and other chemical analytics in earlier studies have confirmed the equilibrium stoichiometry between LMW-LC chitosan and cellulose present in paper. This property may be due the fact that LMW-LC presents with greater area (homogeneity) and hence scope for inter fibre bond formation than MMW-HC. When it comes to wet end addition, chitosan (concentration ∼1–3%) has also been reported to improve the burst strength by 20–30%, breaking length by 20–30% and wax pick number (or surface strength index) by ∼2 units in paper boards from reclaimed pulp (Bhardwaj, Bhardwaj & Negi, 2016). Wax pick number is the average highest numerical designation of the wax that does not disturb the surface of the paper. It is also called the Critical Wax Strength Number and it corresponds to the surface strength of paper. Generally, a pick occurs when the surface of the paper specimen blisters, breaks, or lifts and/or coating substance adheres to the surface of the wax. Chitosan, chitosan derivatives like cyanoethyl chitosan (Fig. 3) and other biopolymers (e.g. carboxymethyl cellulose etc.) have also been found to have synergistic effects on paper strength properties (Bhardwaj et al., 2016; Nada, El-Sakhawy, Kamel, Eid & Adel, 2006). The dielectric properties and thermal stabilities also improve in paper by the addition of chitosan derivatives. Chitosan in solution form (in acetic acid) has been found to

confer antimicrobial properties against both gram positive and gramnegative bacteria in paper. Evidently, the diverse array of functional attributes makes chitosan a promising bio-polymeric additive for paper industry (Bhardwaj et al., 2016; Fatehi et al., 2010; Fernandes et al., 2010; Habibie et al., 2016; Miranda et al., 2013; Nada et al., 2006; Nassar, El-Sakhawy, Madkour, El-ziaty & Mohamed, 2014; Rastogi & Samyn, 2015; Vainio & Paulapuro, 2005; Zakaria et al., 2015). 5. Proteins 5.1. Soy-based Soy flour is an abundantly available bio-product of soybean oil industry that has been reported to be comprised of 51% protein, containing 18 polar and non-polar amino acids. The polar amino acids take part in inter-fibre bonding through chemical cross-links thereby conferring enhanced mechanical, thermal and hydrophilic properties. Crosslinked soy protein has been proved to have increased the mechanical strength of bio-degradable polymers and paper (Chabba, Matthews & Netravali, 2005; Dastidar & Netravali, 2013; Kellor, 1974). Chemically cross-linked [by using diethylenetriaminepentaacetic acid (DTPA) and sodium hypophosphite] and conjugated soy protein (with chitosan) have been explored for strength enhancing effects on virgin as well as recycled (hornified) pulp fibres. The same has been found to have increased tensile index of different types of pulp. In a detailed study of soy flour (Salam et al., 2015), the authors established the capability of soy flour glycoprotein as a mechanical property enhancer. In the mentioned study, when added at a concentration of 1.5% on reclaimed pulp, soy flour glycoprotein has increased the tensile and burst indices of handsheets by ∼5%. Soy flour protein also under similar conditions enhanced the tensile and burst indices by ∼5%. Soy flour protein conjugated with chitosan increased the tensile and burst indices by ∼20% whereas soy flour glycoprotein enhanced the same by ∼10% and 20% respectively. Soy flour protein (as well as glycoprotein) conjugated with DTPA and chitosan increased the tensile and burst indices by ∼50%. Soy flower glycoprotein-DTPA-chitosan conjugate (1%) improved the tensile index of reclaimed and kraft pulp handsheets by 52.6% and 57.8% respectively; burst index by 39.2% and 42.5% respectively and compression index by 39.9% and 48.6% respectively. The superlative rise in mechanical properties are conferred by intense inter-fibre bond formation (H-bond and esterification) by -OH, -COOH and -NH2 functional groups in glycoprotein conjugates. In addition to the soy protein, cotton seed protein was also used as a wet and dry strength additive in paper (Cheng, Villalpando, Easson & Dowd, 2017). 5.2. Cottonseed protein The global production of cottonseed accounts to 39–44 million metric tons (MMT) per annum during the year 2014–17 which imply 8.3 8

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to 9.4 MMT availability of cotton seed protein (Balandrán-Quintana, Mendoza-Wilson, Montfort, & Huerta-Ocampo, 2019). Globulins are the predominant cottonseed proteins followed by albumins and gliadins. Utilization of cotton seed protein as a wet and dry strength additive in paper was studied by Cheng et al., 2017. The authors reported that on addition of 11% cottonseed solution to paper, the dry and wet strength increased by 33 and 16% respectively. Moreover, the combined use of cottonseed protein and an acid (acetic, adipic, aspartic, and citric acids) to promote adhesion resulted in even greater dry paper strength as compared to wet strength of paper. Since very limited work has been done on the use of cotton seed protein as strength additive during paper manufacturing, there is a scope for research and development.

glutens can be classiﬁed as gliadins (alcohol soluble) and glutenins (alcohol insoluble). Commercially available glutens (purity 80–90%) can be used in coating formulations for improved oxygen as well as chemical contaminant (grease) barriers in paperboards and packaging materials (Guazzotti et al., 2014). Wheat gluten, corn gluten and calcium caseinate have been combined to generate coating formulations and their relative adsorption rates were determined with chemical analytics. Wheat gluten has superior adsorption potential followed by corn gluten and caseinate; however, the relative amount varies with raw material of the paperboards (Andersson, 2008; Gastaldi, Chalier, Guillemin & Gontard, 2007; Guazzotti et al., 2014). 6. Gums

5.3. Casein based 6.1. Alginates Caseins are special classes of phosphorylated proteins (𝛼 S1 -, 𝛼 S2 -, 𝛽- and 𝜅-caseins) with high surface activity present in milk in an aggregated form. 𝛼- and 𝛽-Caseins although has the tendency to precipitate in low ionic solutions, 𝜅-casein oppose the precipitation, forming stable colloidal suspensions. Caseinates (sodium, calcium) are generated by precipitating casein micelles through lowering the pH of milk to 4.6. The property of caseinates to generate stable colloids and selfassembly makes it a promising agent imparting superior bonding capabilities as well as electrostatic attractions. Caseinates have been found to form stable ﬁlms in aqueous medium due to inter-chain cohesion. They have also been shown to improve mechanical properties when used as coating additives in cellulose-based packaging materials (Khaoula Khwaldia, Basta, Aloui & El-Saied, 2014). Strength, moisture barrier, oil barrier and ductile properties of paperboards have improved by coating with sodium caseinate. Combinations of sodium caseinate (10–13%) with carnauba wax (0.8%), mica (1.2%) and glycerol (0.6%) have generated superior coating formulations conferring water vapour barrier and mechanical strength to coated papers. Conjugate of caseinate with chitosan imparts thermal stability as an additive when applied to paper and paper products (Horne, 2002, 2008; Huppertz, 2013; Khwaldia, 2010; Khwaldia et al., 2014, 2006).

Alginates are natural polysaccharides found extensively in brown seaweeds (Family Phaeophyceae) typically from the genera Laminaria and Macrocystis as well as bacterial genera Pseudomonas and Azotobacter. Having a chemical backbone of 𝛽-d-mannuronate and its epimer 𝛼-l-guluronate linked by 1–4 glycosidic bonds (Fig. 4a) (Szekalska, Puciłowska, Szymańska, Ciosek & Winnicka, 2016), alginate may constitute around 40% dry weight of the organism, representing a striking analogy with cellulose in terrestrial plants (Draget, Smidsrød & Skjåk-Bræk, 2005). Bacterial alginate is synthesized by a 12-gene (alggenes) operon family under tight regulation but their polymerization as well as translocation is poorly understood (Draget et al., 2005; Remminghorst & Rehm, 2006a, 2006b; Remminghorst, Hay & Rehm, 2009). Alginates are used as thickening, stabilizing, adhesive and filmforming agents (Shen et al., 2014). Alginates are produced on a commercial scale in the form of fine fibres as sodium and/or calcium ionic forms. Sodium alginate (SA) by virtue of its film-forming ability has been proven to have enhanced bonding homogeneity with paper fibres and can be successfully utilized in combination with other additives/complexes resulting improved dry as well as wet strength (Rhim, Lee & Hong, 2006). SA has been used in eco-friendly paper additive formulations by Song, Yao and Jin (2012). From the study it was observed that, SA enhanced the adsorption of poly-electrolytes on papersheets (from bleached pine kraft pulp) and subsequently enhanced the tensile index by a maximum of ∼40–45%. Algin has also been combined with natural gums (guar, tamarind kernel polysaccharide) and used in pigment coating as well as surface sizing agents Yin & Lewis (1981). However, hydrophilic properties of alginate limits its application since it decreases water resistivity of paperboard (Hay, Rehman, Moradali, Wang & Rehm, 2013; Rhim et al., 2006; Rinaudo, 2014; Song et al., 2012; Yin & Lewis, 1981).

5.4. Whey proteins Whey proteins comprise of 18–20% of total milk proteins primarily constituted by 𝛼-lactalbumin and 𝛽-lactoglobulin. Other smaller fractions like serum albumin, immunoglobulins, lactoferrin, lactolin etc. are also present in whey protein. The diversity of amino acid composition gives whey protein high levels of structural complexities. Whey protein is heat labile and its thermal denaturation is dependant upon the pH of the medium (denaturation is inversely proportional to pH). Heat dependant co-aggregation is another astounding property of whey protein. Heat denaturation exposes the sulphahydril groups in lactoglobulins and makes it susceptible to form disulphide bonds with other proteins in the vicinity. Whey protein isolate/cellulose-based ﬁlms, produced by the action of glycerol in aqueous medium with glutaraldehyde and cellulose xanthate was combined with bee wax to form a bilayer coating system onto paperboards by heating compression (Han, Salmieri, Le Tien & Lacroix, 2010). The coating improves water barrier capacities by diminishing WVTR by 77–78%. Whey protein concentrates (80% w/w, plasticized with glycerol, sorbitol or polyethylene glycol) have also been proved to impart superior grease resistance capability hence facilitating long term storage of paperboards (Andersson, 2008; Han et al., 2010; Jovanovi, Bara & Ma, 2005; Lin & Krochta, 2003).

6.2. Guar gum Guar gum is a versatile and popular plant-based gum (exudate) obtained from Guar plant (Cluster bean or Cyamopsis tetragonolobus; Family: Leguminosae). The natural gum contains around 87% polysaccharide composed primarily of poly-d-galactose and d-mannose unitsusually in the ratio of 1:2 (polygalactomannans). The linear 𝛽-dmannopyranosyl chain has side branches of 𝛼-d-galactopyranosyl units (Fig. 4b) (Mudgil, Barak & Khatkar, 2014). Guar gum has the astounding property of maintaining a solution of constant viscosity for a prolonged period either in unmodiﬁed form or modiﬁed forms (oxidized, carboxymethylated, hydroxyalkylated etc.). Guar gum although like other galactomannan gums serve as thickeners in textile and paper industries; it has applications in various other industries on a commercial scale. Dasgupta (1999) emphatically established the strength enhancing effects of cationic and anionic guar gum by using wide range of commercially available gum forms. The study demonstrates that anionic guar gum (by reacting guar gum with caustic soda followed by monochloroacetate, propylene oxide etc. generating carboxymethyl, hydroxypropyl

5.5. Glutens Glutens are abundant storage proteins typically found in wheat and corn. The diverse protein constituents of gluten make it highly viscous and elastic. Additionally, the low hydrophilicity of gluten is attributed by its higher non-polar amino acid composition. In a broader sense, 9

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a concentration of 0.5–1.0%) have maximally enhanced the tensile index of paper between ∼10–35%. Higher molecular weight guar gum addition corresponds to considerable increase in paper strength. Usually the guar additives are added in a low pulp consistency and neutral pH (Chudzikowski, 1971; Dasgupta, 1999). A novel blend of guar with, algin and tamarind kernel polysaccharide finds its effective use in paper coating and surface sizing (Yin & Lewis, 1981). Ionic and nonionic guar gum has successfully increased the strength and retention of fillers in tissue paper manufacturing Wang (2013). Moreover, guar gum combined with precipitated calcium carbonate and organic titanium enhances fibre cross-linking and higher retention of fillers (by ∼2–8%) in paperboards (Chudzikowski, 1971; Dasgupta, 1999; Lee et al., 2005; Wang, 2013; Xie, Song, Liu & Qian, 2016; Yin & Lewis, 1981). 6.3. Carrageenan Carrageenan is a commercially important natural, abundantly available, sulphated polysaccharide (gum) extracted from red algae Gelidium elegans that has promising application in paper science and nanotechnology besides traditional uses in cosmetics, medicine and food thickening (Cadirci et al., 2016; Chen, Lee, Juan & Phang, 2016; Lin, Liang & Chang, 2016; Seo, Lee, Lee & You, 2010). Carrageenan is a polymer with alternate units of galactose and 3.6-anhydrogalactose linked by 𝛽-(1–4) and 𝛼 (1–3) glycosidic bond with 15–40% sulphated monosaccharide units, hence defining its anionic nature (Necas & Bartosikova, 2013). Commercial carrageenans are mainly constituted by three types namely 𝜅-, 𝜄-, and 𝜆-carrageenan. 𝜅-Carrageenan has one sulfate ester, while 𝜄-and 𝜆carrageenan contain two and three sulfates per repeating dimer, respectively. Fig. 4(c)−4(e) shows the structural behaviour of three types of carrageenans (Rhein-Knudsen, Ale & Meyer, 2015). Carrageenan due to its sulphate groups participate in extensive hydrogen bonding with cellulose fibers in paper by abridging the inter-fibre gaps (Liu et al., 2017). As reported earlier, by virtue of this bonding property, carrageenan as an additive confers superior strength in paper, thereby increasing tensile index by ∼25% and burst index by ∼15% when compared to sheets without carrageenan (Huq et al., 2012; Liu et al., 2017; Przybysz, Dubowik, Kucner, Przybysz & Buzała, 2016; Xie et al., 2016). 6.4. Xanthan gum Xanthan gum is produced by gram-negative yellow pigmented bacteria Xanthomonas campestris. The gum has the property to produce stable aggregates (pseudoplasticity) in aqueous medium owing to the capability of forming extensive hydrogen bonding. Hence it generates highly viscous aqueous solution even at low concentrations. Xanthan backbone comprises of pentasaccharide repetitive units having (1–4)-𝛽-dglucopyranose unit along with tri-sachharide lateral branches attached at every C-3 carbon of the alternate sugar residue of the main chain. The lateral chains consist of 𝛽-d-mannopyranose residue linked to (1– 4) 𝛽-d-glucuronic acid which is linked with (1–2) 𝛼-d-mannopyranose residue. Apart from these, pyruvate acetal groups are present at the end of d-mannopyranose (C6-OH position) unit (Patel, Maji, Moorthy & &Maiti, 2020). Fig. 4(f) represents the complex structure of xanthan gum (Patel et al., 2020). The chemical complexity of xanthan provides its capability of bonding and rheological modifications. Industrially used xanthan gum has 37% glucose, 43.4% mannose, 19.5% glucuronic acid, 4.5% acetate and 4.4% pyruvate (Lachke, 2004). Xanthan gum used alone and in combination with other gums and polyelectrolytes as wetend additive increases the tensile strength of paper (Mukherjee et al., 2014). Taggart, Schuster and Schellhamer (1992) showed that xanthan has promising capabilities as both retention aid and strength enhancer when used with starch on kraft-softwood mixed pulp. In the study, retention of starch was reported to increase by 60–70% by separately adding xanthan. The same also increased the tensile index by ∼10% and burst index by ∼35%. Besides these, xanthan has been effectively used as a

Fig. 4. Structures of common gums used as additive in paper making (a) Sodium alginate; (b) guar galactomannan; (c) 𝜅-carrageenan; (d) 𝜆-carrageenan; (e) 𝜄carrageenan; (f) xanthan.

derivatives) and cationic guar (derivatized with glycidyltrimethylammonium chloride) in synergism or alone enhances the tensile index of paper without compromising with the softness, when added to a bleached pulp furnish. Cationic guar alone (at a concentration of 1.0%) has been reported to increase tensile strength by ∼15%; whereas anionic guar (at a concentration of 1.0%) enhances the tensile index by ∼17% (Dasgupta, 1999). The blends of cationic and anionic guar (at

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ﬂocculant, paper coating agent and a rheology modiﬁer for high size press in paper manufacturing (Castro & Cheng, 2014; Lachke, 2004; Mukherjee et al., 2014; Taggart et al., 1992).

and paper industries when compared with synthetic chemical additives. With the constantly increasing price of petro-chemicals and fossil fuel based chemicals, it is important to understand the economic and environmental need to switch from chemical to renewable bio-based polymers. Most of these bio-materials are abundant and cheap (e.g. cellulose and starch based products). Furthermore, these bio-polymers can be obtained/ recycled from natural and household wastes. Recent research (Díez-Pascual, 2019) highlighted these aspects while discussing the production, impact and economical signiﬁcance of bio-based polymers in the manufacture of bio-composites. It was mentioned that although the cost of production of bio-polymers is a matter of concern, the same can be compensated from the functional diversity, properties and eco-friendliness. The approximate average price range of various commercially available biopolymers has been reviewed from the latest price lists of reputed manufactures and listed in Table 3 to provide a perspective on the commercial viability of bio-based polymers. However, a comparative economic blue-print comprising the utilization of synthetic and bio-based polymers has not yet been devised. Hence, there is an ample scope of research and analysis in order to design sustainable industrial practices in future.

7. Other bio-based polymeric additives of importance Molasses extracted from sugarcane have recently been explored as a potential additive in paper industry (Fahmy, 2014). It comprises of around 32–44% sucrose, besides trace amount glucose and fructose. Molasses also contains 3–5% gums (and starch). Sucrose interactions with cellulose ﬁbrils happen to enhance breaking length and water uptake of paper. Molasses at a concentration of 15–20% (w/w) has been reported to increase the dry breaking length (by −10%), wet breaking length (by ∼6%) and water retention value (by ∼30%) in paperboards (Allan et al., 2005; Allan, Stoyanov, Ueda & Yahiaoui, 2001; Fahmy, 2014, 2006). Tamarind kernel powder or tamarind kernel polysaccharide (TKP) is another commercially available xyloglucan obtained by husking and milling seed kernels of Tamarindus indica Linn. TKP blended with algin and guar has been used a size press solution, pigment coating formulation, ink hold-out agent and water retention additive in paper manufacturing (Yin & Lewis, 1981). This novel blend imparts properties as thickener, emulsiﬁer, stabilizer, lubricator, binder and chemical stabilizers. Crude TKP has successfully substituted the conventional wet end additives like starch and galactomannans in paper-making. TKP xyloglucan when used with NFC has been found to enhance the tensile strength and TEA of unbeaten softwood pulp by ∼20–30% (Goyal, Kumar & Sharma, 2008; Sehaqui, 2013; Yin & Lewis, 1981).

10. Future strategy The consistently high consumption of paper and paper based products eventually increases the demand of chemical additives in order to meet the needs of the industry. As discussed in this review, additives perform a wide array of functions starting from surface engineering (surface strength, barrier properties, sizing, coating, enhancing the shelf-life, recyclability etc.) to mechanical strength enhancement (tear, tensile etc.) and from retention aid (for fines, filler, other additives etc.) to paper rheology modifications. Hence, additives form an inseparable domainin pulp and paper manufacturing. The production, availability, chemistry and specific utility of chemical additives are well known to paper technologists and are extensively utilized in paper manufacturing (Bajpai, 2015; Hubbe, Nanko & McNeal, 2009; Pelton & Hong, 2002). However, it is important to understand the consequences of using these harmful chemicals on an environmental perspective. Hundreds of hazardous chemicals and their derivatives are generated during the papermaking process and are released as mill effluents (Ali & Sreekrishnan, 2001). Although effluent recycling and treatments are devised to minimize such risks, the same measures are unable to completely mitigate the potential long term hazards of these harmful chemicals (Bajpai, 2017; Cesaro, Belgiorno, Siciliano & Guida, 2019). Hence, to cut-down the hazards of chemical additives, the present review discusses the significance of polymers derived from nature that are potential functional substitutes of chemical additives in paper industries. Besides being eco-friendly and biologically benign, the striking feature of bio-polymeric additives is their versatility i.e., one biopolymer can be used to impart diverse functions even at very low concentrations. In other words, a single bio-polymer additive carries the potential to substitute a group of chemical additives used in paper production (Table 2). Secondly, the chemical make-up of bio-polymers shows compatibility with cellulose fibrils and synergism with other bio-polymers; hence can be used in innumerable combinations as per requirement. Finally, bio-polymers can be obtained from abundant, and renewable resources. However, modified bio-polymers, are often criticized on a commercial perspective considered their higher production cost. Having considered such limitations, wide array of bio-polymers are available that can be concurrently produced in paper industries (e.g., modified cellulose, modified starch, modified gums etc.), hence transforming a paper mill into an integrated one for additional revenue and employment opportunities (Hamaguchi, 2013). Table 4 summarises the sources and application of potential bio-polymeric additives that can be used in paper industries.

8. Environmental perspective The pulp and paper industry has been designated as one of the most notoriously polluting industries on a global scale. The intense manufacturing processes not only generate hazardous chemicals, gases and toxic water in leaps and bounds but also produces huge amount of sludge comprised of fibres (Bajpai, 2017; Hashim & Sen Gupta, 1998; Veluchamy & Kalamdhad, 2017). Adsorbable organic halides (AOX), heavy metals, sulphide gases, phenolics, suspended particles, acids and various other detrimental compounds are produced and released in the environment. These compounds not only pollute the habitat and disrupt the food chain, but also affect the systemic and genetic make-up of microscopic to large organisms adversely (Antoni Ginebreda et. al., 2006; Lacorte et al., 2003). A unique utility of biopolymers was devised by researchers that focuses on the recycling of fibres from effluents. In their study, commonly used bio-polymeric additives like guar gum, xanthan gum and locust bean gum were employed to recover cellulosic fibres from paper-mill effluent. Guar gum proved to be the most promising bio-polymeric flocculent as compared to chemical flocculent (alum) with a capability of removing turbidity of paper-mill effluent by ∼95% (Mukherjee et al., 2014). Recently, Dixit, Gupta, Liu and Shukla (2019) have brilliantly highlighted the environmental health aspect of pulp and paper mill pollutants in detail. The study also describes state of art techniques in waste recycling and the scope of eco-friendly measures. In this context, the commonly used chemical additives and the potential environmental threats from them can be overviewed. Table 2 represents some of the functional chemical additives used widely in paper industry, the potential hazards from these chemicals and corresponding bio-polymeric additives that have the potential to execute similar functions. 9. Economy and prospects The commercialization of biopolymers on a global scale is still at its naive stage. Moreover, there is no authentic scientific report that discusses the economy related to the application of bio-polymers in pulp

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Table 2 Common chemical additives in paper industries and their ill-eﬀects. Function in Paper Industry

Common chemical additives in paper industries (Antoni Ginebreda et. al., 2006)

Retention aids

Polyaluminium chloride (PAC) Bentonite Polyacrylamide (PAM)

Polyethylenimine (PEI)

Polyvinylamine (PVA)

Sizing agents

Alkyl ketene dimer (AKD)

Styrene derivatives

Rosin

Strength additive

Urea formaldehyde (UF)

Melamine formaldehyde (MF)

Poly-amideamine epichlorohydrin (PAE) Coating agents

Titanium dioxide

Styrene-butadiene

Polyvinyl compounds Diaminostilbenedisulphonic acid derivatives

Harmful eﬀect(s) of the chemicals

Bio-polymers imparting similar functions

Decreases pH of water bodies; lethal to aquatic zooplanktons (Jančula, Mikula & Maršálek, 2011) Cytotoxic and neurotoxic effect in animals (Nones, Riella, Trentin & Nones, 2015) Carcinogenic; mutagenic, teratogenic, epidermiological effects, metabolic distress to aquatic organisms, neurotoxic etc. (King & Noss, 1989) Detrimental to microbial population in the environment (bacteria and fungi), eco-toxic (Mortimer, Kasemets, Heinlaan, Kurvet & Kahru, 2008) Detrimental to microbial population in the environment (Westman, Ek, Enarsson & Wågberg, 2009) Toxic to ﬁshes and microbial population (Demirel, Güdül, Temiz, Kustas & Aydin, 2018; Hermens, 1990) Detrimental to microbial population, hepatotoxic effects, carcinogenic effects (Loprieno et al., 1976; Vodicka et al., 2006) Risk of systemic toxicity and genotoxic effect in grazing animals (Stegelmeier, Gardner, James, Panter & Molyneux, 1996) Risks of respiratory diseases, allergies, systemic disorders, neurotoxic effects (L’Abbé & Hoey, 1984; Norman & Newhouse, 1986; Songur, Ozen & Sarsilmaz, 2010) Detrimental to phytoplanktons, risks of male infertility, systemic effects, neurotoxic effects (Hall & Mirenda, 1991; Khalil, Awad & Ali, 2017; Songur et al., 2010) Causes male infertility; mutagenic; carcinogenic (Eder & Weinfurtner, 1994; Velí’scar, Davídek, Davídek & Hamburg, 1991) Systemic toxicity in ﬁshes and small mammals (Chen, Dong, Zhao & Tang, 2009; Federici, Shaw & Handy, 2007; Wang et al., 2007) Carcinogenic effects, mutagenic effects, risks of respiratory disorders (Anttinen-Klemetti, Vaaranrinta, Mutanen & Peltonen, 2006; Ward et al., 1996) Immunogenic effects, hepatotoxic effects in small mammals (DeMerlis& Schoneker, 2003) Non-degradable, deposits in waste water (Wong-Wah-Chung, Mailhot & Bolte, 2001)

Cationic starch, molasses, guar gum, xanthan gum

Table 3 Approximate costs of commercially available biopolymers. Type

Quantity (g)

Approximate Price (in INR)#

Microcrystalline cellulose (powder) Cellulose acetate Hydroxyethyl cellulose (quaternized) Hydroxypropyl cellulose Hydroxypropyl-methyl cellulose Sodium carboxymethyl cellulose Alginate-sodium salt Chitosan Starch∗∗ Hydroxyethyl starch 𝜅- Carrageenan 𝜆- Carrageenan Wheat gluten Tamarind kernel powder Carboxymethyl tamarind kernel powder Whey protein powder Casein-protein powder

250 500 50 250 100 1000 500 250 250 500 100 25 500 1000 1000 1000 1000

2000–3000 8000–10,000 7000–9000 19,000–22,000 8000–11,000 10,000–12,000 5000–7000 20,000–25,000 2000–14,000 12,000–13,000 12,000–13,000 48,000–50,000 1000–3000 40–50 60–80 800–2000 600–2000

# ∗∗

Price is based on high to highest purity;. Price range is based on diﬀerent sources of starch.

Starch, oxidized starch, cellulose derivatives, cationic cellulose, alginate, casein, whey proteins, chitosan, tamarind kernel polysaccharide, hemicellulose, polyhydroxyalkanoates

Cellulose derivatives, cationic starch, hemicellulose, chitosan, alginate, guar gum, tamarind kernel polysachharide, carrageenan, xanthan, poly‑hydroxy-alkanoates

Cellulose derivatives, cationic starch, hemicellulose, chitosan, alginate, guar gum, tamarind kernel polysachharide, carrageenan, xanthan, poly‑hydroxy-alkanoates, glutens

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Table 4 Overview of sources, types and applications of bio-based polymers in paper making. Source

Classes of Bio-polymers

Crop grains (wheat, rice, maize etc.) Tubers (cassava, potato)

Starch

Plant biomass (woody and non-woody) Fibre wastes Bacteria (various genera)

Cellulose

Plant biomass (woody & non-woody) Leguminous seeds

Hemi-celluloses

Crustaceans Molluscs Insects Fungi Brown seaweed (family Phaeo-phyceae) Bacteria Milk (casein, whey) Soy Wheat & Corn (gluten)

Chitosan

Derived from natural carbohydrates by fermentation using Lactobacillus sp. Tamarindus indica Linn. Bacteria (Pseudomonas sp., Alcaligenes spetc.) Sugar cane (Saccharum oﬃcinarum) Sea weed (Gelidium elegans) Guar plant (Cyamopsis tetragonolobus) Bacteria (X. campestris)

Alginate

Types and derivatives Unmodiﬁed starch Oxidized starch Hydroxyethyl starch Acetyl starch Cationic starch

Carboxymethyl cellulose Hydroxyethyl cellulose Methyl cellulose Hydroxypropyl cellulose Hydroxypropyl methyl cellulose - Nanocellulose - Cationic cellulose

–

References

Sizing, pigment coating, dry strength additive, wet strength additive, retention aid

(Andersson, 2008; Ghasemian et al., 2012; Hermansson & Svegmark, 1996; Holik, 2006; Kochkar, Morawietz & Hölderich, 2001; Lindström et al., 2016; Ray, Ghosh, Gupta & Rajrana, 2011; Ulbrich et al., 2012; Vanier et al., 2017; Zakrajšek & Golob, 2009) (Abdel-Halim, 2014; Ahola et al., 2008; Hamada, Beckvermit & Bousﬁeld, 2010; Holik, 2006; Joshi et al., 2015; Karrasch et al., 2009; Khwaldia, 2013; Khwaldia, Arab-Tehrany & Desobry, 2010; Klass, 2011; Moral et al., 2015; Pajari et al., 2012; Salam et al., 2015; Shen et al., 2014; Sothornvit, 2009;, Lavanya et al., 2011) (Anjos et al., 2004; Denis U. Lima et al., 2003; Mobarak & Fahmy, 1973; Shen et al., 2014) (Fernandes et al., 2010; Nada et al., 2006; Nicu, Bobu & Desbrieres, 2011; Zakaria et al., 2015) (Song et al., 2012; Yin & Lewis,1981)

Dry strength additive, wet strength additive, coating, sizing

Tear & tensile strength, sizing and surface strength

- Unmodiﬁed chitosan - Cyanoethyl chitosan - Carboxymethyl chitosan –

Protein-based polymers

Functions

Strength, sizing, barrier, thermal stability, antimicrobial properties Dry and wet strength; sizing and coating

Casein based Whey protein Soy based Glutens

Dry strength additive, sizing and coating (barrier properties)

(Andersson, 2008; Guillaume, Pinte, Gontard & Gastaldi, 2010; Khwaldia et al., 2006; Salam et al., 2015)

Poly-lactic acid (PLA)

–

Mechanical strength, Coating

(Jamshidian, Tehrany, Imran, Jacquot & Desobry, 2010)

Tamarind kernel powder (TKP)

–

Polyhydroxy-alkanoates (PHA)

–

Molasses

–

Water retention, sizing, binders, coating Tensile strength, barrier properties; Sizing and coating Dry and wet strength additive, Retention aid Dry strength additive, soating, rheology modiﬁer, retention aid

(Goyal et al., 2008; Yin & Lewis,1981) (Arrieta et al., 2014; Kuusipalo, 2000a, 2000b) (Fahmy, 2014)

Gums

- Carrageenan - Guar gum (cationic and anionic) - Xanthan gum

11. Conclusion

(Dasgupta, 1999; Liu et al., 2017;Lachke, 2004; Taggart et al., 1992)

3 Decrease toxicity/reduce harmful eﬀects from chemical processes and mill-eﬄuents

Available literatures suggest that the specific properties imparted by bio-polymeric additives differ adversely with varying raw material type and reaction conditions. Hence, intensive research and development is necessary to utilize bio-polymeric resources with well defined reaction parameters specific to individual raw materials. This in turn will help in formulating sustainable industrial protocols. To conclude, it can be said that the scope of biopolymers in paper industry is well attributed from the three functional domains that a potential paper additive must address such as:

From the present review, it can be understood that biopolymers have the potential to administer all aforesaid aspects. In this context it can also be mentioned that our research group is relentlessly working on potential bio-polymeric blend formulations to generate economically viable additives for quality paper manufacturing. Credit author statement Soumya Basu: Literature survey, writing and editing. Shuank Malik: Literature survey, writing and editing. Gyanesh Joshi: Inspection and validation of referred literature. P. K. Gupta: Writing and suggestions for content. Vikas Rana: Conceptualization, writing and editing.

1 Minimize chemical and energy charge of industrial paper manufacturing (hence, the production cost) 2 Enhance the quality of the ﬁnal product. 13

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Declaration of Competing Interest

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Sothornvit, R. (2009). Effect of hydroxypropyl methylcellulose and lipid on mechanical properties and water vapor permeability of coated paper. Food Research International, 41, 307–311. https://doi.org/10.1016/j.foodres.2008.12.003. Stegelmeier, B. L., Gardner, D. R., James, L. F., Panter, K. E., & Molyneux, R. J. (1996). The toxic and abortifacient effects of ponderosa pine. Veterinary Pathology, 33, 22–28. https://doi.org/10.1177/030098589603300103. Strand, A., Sundberg, A., Retulainen, E., Salminen, K., Oksanen, A., Kouko, J., et al. (2017). The effect of chemical additives on the strength, stiffness and elongation potential of paper. Nordic Pulp & Paper Research Journal, 32, 324–335. https://doi.org/10.3183/ npprj- 2017- 32- 03- p324- 335. Su, Y., Du, H., Huo, Y., Xu, Y., Wang, J., Wang, L., et al. (2016). Characterization of cationic starch flocculants synthesized by dry process with ball milling activating method. International Journal of Biological Macromolecules, 87, 34–40. https://doi.org/10.1016/ j.ijbiomac.2015.11.093. Syverud, K., & Stenius, P. (2009). Strength and barrier properties of MFC films. Cellulose (London, England), 16, 75. https://doi.org/10.1007/s10570- 008- 9244- 2. Szekalska, M., Puciłowska, A., Szymańska, E., Ciosek, P., & Winnicka, K. (2016). Alginate: Current use and future perspectives in pharmaceutical and biomedical applications. International Journal of Polymer Science, 2016, Article 7697031. https://doi.org/10. 1155/2016/7697031. Taggart, T.E., .Schuster, M.A., .& Schellhamer, A.J. (.1991). Papermaking using cationic starch and carboxymethyl cellulose or its additionally substituted derivatives. Patent No. 5061346. US Patent Office. Taggart, T.E., .Schuster, M.A., .& Schellhamer, A.J. (.1992). Papermaking using cationic starch and naturally anionic polysacchride gums. Patent No. 5,104,487. United States Patent office. Tang, Y., Zhou, D., Zhang, J., & Zhu, X. (2013). Fabrication and properties of paper coatings with the incorporation of nanoparticle pigments: Rheological behavior. Digest Journal of Nanomaterials and Biostructures, 9, 1407–1416. Tarrés, Q., Oliver-Ortega, H., Alcalà, M., Merayo, N., Balea, A., Blanco, Á., et al. (2018). Combined effect of sodium carboxymethyl cellulose, cellulose nanofibers and drainage aids in recycled paper production process. Carbohydrate Polymers, 183, 201– 206. https://doi.org/10.1016/j.carbpol.2017.12.027. Thacker, N. P., Nitnaware, V. C., Das, S. K., & Devotta, S. (2007). Dioxin formation in pulp and paper mills of India. Environmental Science and Pollution Research International, 14, 225–226. https://doi.org/10.1065/espr2007.02.386. Tijsen, C. J., Kolk, H. J., Stamhuis, E. J., & Beenackers, A. A. C. M. (2001). An experimental study on the carboxymethylation of granular potato starch in non-aqueous media. Carbohydrate Polymers, 45, 219–226. https://doi.org/10.1016/S0144- 8617(00)00243- 5. Tomasik, P., & Zaranyika, M. F. (1995). Nonconventional Methods of Modification of Starch. In Advances in carbohydrate chemistry and biochemistry: 51 (pp. 243–318). https: //doi.org/10.1016/S0065- 2318(08)60195- X. Ulbrich, M., Radosta, S., Kießler, B., & Vorwerg, W. (2012). Interaction of cationic starch derivatives and cellulose fibres in the wet end and its correlation to paper strength with a statistical evaluation. Starch/Staerke, 64, 972–983. https://doi.org/10.1002/ star.201200033. Vainio, A., & Paulapuro, H. (2005). Observations on interfibre bonding and fibre segment activation based on the strength properties of laboratory sheets. Nordic Pulp and Paper Research Journal, 20, 340–344. https://doi.org/10.3183/ npprj- 2005- 20- 03- p340- 344. Vanier, N. L., El Halal, S. L. M., Dias, A. R. G., & da Rosa Zavareze, E. (2017). Molecular structure, functionality and applications of oxidized starches: A review. Food Chemistry, 221, 1546–1559. https://doi.org/10.1016/j.foodchem.2016.10.138. Varshney, V. K., Gupta, P. K., Naithani, S., Khullar, R., Bhatt, A., & Soni, P. L. (2006). Carboxymethylation of 𝛼-cellulose isolated from Lantana camara with respect to degree of substitution and rheological behavior. Carbohydrate Polymers, 63, 40–45. https://doi.org/10.1016/j.carbpol.2005.07.001. Varshney, V. K., & Naithani, S. (2011). Chemical functionalization of cellulose derived from nonconventional sources. In Cellulose fibers: Bio- and Nano-Polymer composites (pp. 43–60). https://doi.org/10.1007/978- 3- 642- 17370- 7_2. Vásconez, M. B., Flores, S. K., Campos, C. A., Alvarado, J., & Gerschenson, L. N. (2009). Antimicrobial activity and physical properties of chitosan-tapioca starch based edible films and coatings. Food Research International, 42, 762–769. https://doi.org/10. 1016/j.foodres.2009.02.026.

Velí’scar, J., Davídek, T., Davídek, J., & Hamburg, A. (1991). 3-Chloro-1,2-propanediol derived amino alcohol in protein hydrolysates. Journal of Food Science, 56, 136–138. https://doi.org/10.1111/j.1365-2621.1991.tb07994.x. Veluchamy, C., & Kalamdhad, A. S. (2017). Influence of pretreatment techniques on anaerobic digestion of pulp and paper mill sludge: A review. Bioresource Technology, 245, 1206–1219. https://doi.org/10.1016/j.biortech.2017.08.179. Venica, A. D., Chen, C. L., & Gratzl, J. S. (2008). Soda–AQ delignification of poplar wood. Part 1: Reaction mechanism and pulp properties. Holzforschung, 62, 627–636. Vincken, J. P., De Keizer, A., Beldman, G., & Voragen, A. G. (1995). Fractionation of xyloglucan fragments and their interaction with cellulose. Plant Physiology, 108, 1579– 1585. https://doi.org/10.1104/pp.108.4.1579. Vodicka, P., Koskinen, M., Naccarati, A., Oesch-Bartlomowicz, B., Vodickova, L., Hemminki, K., et al. (2006). Styrene metabolism, genotoxicity, and potential carcinogenicity. Drug Metabolism Reviews, 38, 805–853. https://doi.org/10.1080/ 03602530600952222. Wang, J., Zhou, G., Chen, C., Yu, H., Wang, T., Ma, Y., et al. (2007). Acute toxicity and biodistribution of different sized titanium dioxide particles in mice after oral administration. Toxicology Letters, 168, 176–185. https://doi.org/10.1016/j.toxlet.2006.12. 001. Wang, Y. (2013). Application of guar gum in tissue paper manufacture. Chung-Kuo Tsao Chih/China Pulp and Paper, 20. Retrieved from http://en.cnki.com.cn/Article_en/CJFDTotal-ZGZZ201308020.htm. Ward, J. B., Ammenheuser, M. M., Whorton, E. B., Bechtold, W. E., Kelsey, K. T., & Legator, M. S. (1996). Biological monitoring for mutagenic effects of occupational exposure to butadiene. Toxicology, 113, 84–90. https://doi.org/10.1016/0300-483X(96) 03431-2. Watanabe, M., Gondo, T., & Kitao, O. (2004). Advanced wet-end system with carboxymethyl-cellulose. Tappi Journal, 3, 15–19. Westman, E. H., Ek, M., Enarsson, L. E., & Wågberg, L. (2009). Assessment of antibacterial properties of polyvinylamine (PVAm) with different charge densities and hydrophobic modifications. Biomacromolecules, 10, 1478–1483. https://doi.org/10. 1021/bm900088r. Wong-Wah-Chung, P., Mailhot, G., & Bolte, M. (2001). 4,4′-Diaminostilbene-2,2′disulfonate (DSD) behaviour: Under irradiation in water.: Decrease of its activity as a fluorescent whitening agent. Journal of Photochemistry and Photobiology A: Chemistry, 138, 275–280. https://doi.org/10.1016/S1010- 6030(00)00400- 7. Xie, F., Yu, L., Liu, H., & Chen, L. (2006). Starch modification using reactive extrusion. Starch/Staerke, 58, 131–139. https://doi.org/10.1002/star.200500407. Xie, W., Feng, H. L., & Qian, X. R. (2008). Preparation and application of cationized pulp fiber as a papermaking wet-end additive. Journal of Forestry Research, 19, 235–238. https://doi.org/10.1007/s11676- 008- 0039- y. Xie, W., Song, Z., Liu, Z., & Qian, X. (2016). Surface modification of PCC with guar gum using organic titanium ionic crosslinking agent and its application as papermaking filler. Carbohydrate Polymers, 150, 114–120. https://doi.org/10.1016/j.carbpol.2016. 05.010. Yang, H., Qiu, L., Qian, X., & Shen, J. (2013). Filler modification for papermaking with cationic starch and carboxymethyl cellulose: A comparative study. Bioresources, 8, 5449–5460. https://doi.org/10.15376/biores.8.4.5449-5460. Yi, X., Zhang, S., & Ju, B. (2014). Preparation of water-soluble oxidized starch with high carbonyl content by sodium hypochlorite. Starch-Stärke, 66, 115–123. https://doi. org/10.1002/star.201300037. Yin, R.I., .& Lewis, J.G. (.1981). Novel blend of algin, TKP, and guar gum. Patent No. 4257816A. United States Patent office. Zakaria, S., Chia, C. H., Wan Ahmad, W. H., Kaco, H., Chook, S. W., & Chan, C. H. (2015). Mechanical and antibacterial properties of paper coated with chitosan. Sains Malaysiana, 44, 905–911. https://doi.org/10.17576/jsm- 2015- 4406- 18. Zakrajšek, N. (2008). Influence of pulp properties on the adsorption of cationic starch. Tappi Journal, 7, 23–27. Zakrajšek, N., & Golob, J. (2009). The influence of modified starch on the process water quality in papermaking and the paper properties. Starch/Staerke, 61, 109–115. https: //doi.org/10.1002/star.200800009.

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The 8 Most Common Leadership Styles & How to Find Your Own "A good leader should always … " How you finish that sentence could reveal a lot about your leadership style. Leadership is a fluid practice. We're always changing and improving the way in which we help our direct reports and the company grow. And the longer we lead, the more likely we'll change the way we choose to complete the sentence above. But in order to become better leaders tomorrow, we need to know where we stand today. To help you understand the impact each type of leader has on a company, I'll explain what a leadership style is, then share eight of the most common types and how effective they are. Then, I'll show you a leadership style assessment based on this post's opening sentence to help you figure out which leader you are. Written by Braden Becker @BradenBecker Editor's note: This post was originally published in August 2016 and has been updated for comprehensiveness. https://blog.hubspot.com/marketing/leadership-styles

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What is a leadership style? A leadership style refers to a leader’s methods and behaviors when directing, motivating, and managing others. A person’s leadership style also determines how they strategize and implement plans while accounting for the expectations of stakeholders and the wellbeing of their team. Why It’s Important to Know Your Leadership Style Knowing your leadership style is critical because it can help you determine how you affect those whom are under your direct influence. How do your direct reports see you? Do they feel you’re an effective leader? It’s always important to ask for feedback to understand how you’re doing, but knowing your leadership style prior to asking for feedback can be a helpful starting point. That way, when you receive junior employees’ thoughts, you can automatically decide which new leadership style would be best and adopt the style’s characteristics in your day-to-day management duties. Knowing your leadership style may also remove the need for getting feedback. Each leadership style has its pitfalls, allowing you to proactively remediate areas of improvement. This is critical because some employees might hesitate to speak up, even in an anonymous survey. Ready to find out which leadership style you might currently have? Check out the eight most common ones below. Types of Leadership Styles 1. Democratic Leadership 2. Autocratic Leadership 3. Laissez-Faire Leadership 4. Strategic Leadership 5. Transformational Leadership 6. Transactional Leadership 7. Coach-Style Leadership 8. Bureaucratic Leadership 1. Democratic Leadership (Commonly Effective) Democratic leadership is exactly what it sounds like — the leader makes decisions based on the input of each team member. Although he or she makes the final call, each employee has an equal say on a project's direction. Democratic leadership is one of the most effective leadership styles because it allows lower-level employees to exercise authority they'll need to use wisely in future positions they might hold. It also resembles how decisions can be made in company board meetings. For example, in a company board meeting, a democratic leader might give the team a few decision-related options. They could then open a discussion about each option. After a discussion, this leader might take the board's thoughts and feedback into consideration, or they might open this decision up to a vote. 2. Autocratic Leadership (Rarely Effective) Autocratic leadership is the inverse of democratic leadership. In this leadership style, the leader makes decisions without taking input from anyone who reports to them. Employees are neither considered nor consulted prior to a change in direction, and are expected to adhere to the decision at a time and pace stipulated by the leader. An example of this could be when a manager changes the hours of work shifts for multiple employees without consulting anyone — especially the affected employees. Frankly, this leadership style stinks. Most organizations today can't sustain such a hegemonic culture without losing employees. It's best to keep leadership more open to the intellect and perspective of the rest of the team. 3. Laissez-Faire Leadership (Sometimes Effective) If you remember your high-school French, you'll accurately assume that laissez-faire leadership is the least intrusive form of leadership. The French term "laissez-faire" literally translates to "let them do," and leaders who embrace it afford nearly all authority to their employees. Page 2 of 6

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In a young startup, for example, you might see a laissez-faire company founder who makes no major office policies around work hours or deadlines. They might put full trust into their employees while they focus on the overall workings of running the company. Although laissez-faire leadership can empower employees by trusting them to work however they'd like, it can limit their development and overlook critical company growth opportunities. Therefore, it's important that this leadership style is kept in check. 4. Strategic Leadership (Commonly Effective) Strategic leaders sit at the intersection between a company's main operations and its growth opportunities. He or she accepts the burden of executive interests while ensuring that current working conditions remain stable for everyone else. This is a desirable leadership style in many companies because strategic thinking supports multiple types of employees at once. However, leaders who operate this way can set a dangerous precedent with respect to how many people they can support at once, and what the best direction for the company really is if everyone is getting their way at all times. 5. Transformational Leadership (Sometimes Effective) Transformational leadership is always "transforming" and improving upon the company's conventions. Employees might have a basic set of tasks and goals that they complete every week or month, but the leader is constantly pushing them outside of their comfort zone. When starting a job with this type of leader, all employees might get a list of goals to reach, as well as deadlines for reaching them. While the goals might seem simple at first, this manager might pick up the pace of deadlines or give you more and more challenging goals as you grow with the company. This is a highly encouraged form of leadership among growth-minded companies because it motivates employees to see what they're capable of. But transformational leaders can risk losing sight of everyone's individual learning curves if direct reports don't receive the right coaching to guide them through new responsibilities. 6. Transactional Leadership (Sometimes Effective) Transactional leaders are fairly common today. These managers reward their employees for precisely the work they do. A marketing team that receives a scheduled bonus for helping generate a certain number of leads by the end of the quarter is a common example of transactional leadership. When starting a job with a transactional boss, you might receive an incentive plan that motivates you to quickly master your regular job duties. For example, if you work in marketing, you might receive a bonus for sending 10 marketing emails. On the other hand, a transformational leader might only offer you a bonus if your work results in a large number of newsletter subscriptions. Transactional leadership helps establish roles and responsibilities for each employee, but it can also encourage bare-minimum work if employees know how much their effort is worth all the time. This leadership style can use incentive programs to motivate employees, but they should be consistent with the company's goals and used in addition to unscheduled gestures of appreciation. 7. Coach-Style Leadership (Commonly Effective) Similarly to a sports team's coach, this leader focuses on identifying and nurturing the individual strengths of each member on his or her team. They also focus on strategies that will enable their team to work better together. This style offers strong similarities to strategic and democratic leadership, but puts more emphasis on the growth and success of individual employees. Rather than forcing all employees to focus on similar skills and goals, this leader might build a team where each employee has an area of expertise or skillset in something different. In the long run, this leader focuses on creating strong teams that can communicate well and embrace each other's unique skillsets in order to get work done. A manager with this leadership style might help employees improve on their strengths by giving them new tasks to try, offering them guidance, or meeting to discuss constructive feedback. They might also encourage one or more team members to expand on their strengths by learning new skills from other teammates.

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8. Bureaucratic Leadership (Rarely Effective) Bureaucratic leaders go by the books. This style of leadership might listen and consider the input of employees — unlike autocratic leadership — but the leader tends to reject an employee's input if it conflicts with company policy or past practices. You may run into a bureaucratic leader at a larger, older, or traditional company. At these companies, when a colleague or employee proposes a strong strategy that seems new or non-traditional, bureaucratic leaders may reject it. Their resistance might be because the company has already been successful with current processes and trying something new could waste time or resources if it doesn't work. Employees under this leadership style might not feel as controlled as they would under autocratic leadership, but there is still a lack of freedom in how much people are able to do in their roles. This can quickly shut down innovation, and is definitely not encouraged for companies who are chasing ambitious goals and quick growth. Leadership Style Assessment Leaders can carry a mix of the above leadership styles depending on their industry and the obstacles they face. At the root of these styles, according to leadership experts Bill Torbert and David Rooke, are what are called "action logics." These action logics assess "how [leaders] interpret their surroundings and react when their power or safety is challenged." That's the idea behind a popular management survey tool called the Leadership Development Profile. Created by professor Torbert and psychologist Susanne Cook-Greuter — and featured in the book, Personal and Organizational Transformations — the survey relies on a set of 36 open-ended sentence completion tasks to help researchers better understand how leaders develop and grow. Below, we've outlined six action logics using open-ended sentences that help describe each one. See how much you agree with each sentence and, at the bottom, find out which leadership style you uphold based on the action logics you most agreed with. 1. Individualist The individualist, according to Rooke and Tolbert, is self-aware, creative, and primarily focused on their own actions and development as opposed to overall organizational performance. This action logic is exceptionally driven by the desire to exceed personal goals and constantly improve their skills. Here are some things an individualist might say: Individualist 1: "A good leader should always trust their own intuition over established organizational processes." Individualist 2: "It's important to be able to relate to others so I can easily communicate complex ideas to them." Individualist 3: "I'm more comfortable with progress than sustained success." 2. Strategist Strategists are acutely aware of the environments in which they operate. They have a deep understanding of the structures and processes that make their businesses tick, but they're also able to consider these frameworks critically and evaluate what could be improved. Here are some things a strategist might say: Strategist 1: "A good leader should always be able to build a consensus in divided groups." Strategist 2: "It's important to help develop the organization as a whole, as well as the growth and individual achievements of my direct reports." Strategist 3: "Conflict is inevitable, but I'm knowledgeable enough about my team's personal and professional relationships to handle the friction." Page 4 of 6

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3. Alchemist Rooke and Tolbert describe this charismatic action logic as the most highly evolved and effective at managing organizational change. What distinguishes alchemists from other action logics is their unique ability to see the big picture in everything, but also fully understand the need to take details seriously. Under an alchemist leader, no department or employee is overlooked. Here are some things an alchemist might say: Alchemist 1: "A good leader helps their employees reach their highest potential, and possesses the necessary empathy and moral awareness to get there." Alchemist 2: "It's important to make a profound and positive impact on whatever I'm working on." Alchemist 3: "I have a unique ability to balance short-term needs and long-term goals." 4. Opportunist Opportunists are guided by a certain level of mistrust of others, relying on a facade of control to keep their employees in line. "Opportunists tend to regard their bad behavior as legitimate in the cut and thrust of an eye-for-an-eye world," Rooke and Tolbert write. Here are some things an opportunist might say: Opportunist 1: "A good leader should always view others as potential competition to be bested, even if it's at the expense of their professional development." Opportunist 2: "I reserve the right to reject the input of those who question or criticize my ideas." 5. Diplomat Unlike the opportunist, the diplomat isn't concerned with competition or assuming control over situations. Instead, this action logic seeks to cause minimal impact on their organization by conforming to existing norms and completing their daily tasks with as little friction as possible. Here are some things a diplomat might say: Diplomat 1: "A good leader should always resist change since it risks causing instability among their direct reports." Diplomat 2: "It's important to provide the 'social glue' in team situations, safely away from conflict." Diplomat 3: "I tend to thrive in more team-oriented or supporting leadership roles." 6. Expert The expert is a pro in their given field, constantly striving to perfect their knowledge of a subject and perform to meet their own high expectations. Rooke and Tolbert describe the expert as a talented individual contributor and a source of knowledge for the team. But this action logic does lack something central to many good leaders: emotional intelligence. Here are some things a diplomat might say: Expert 1: "A good leader should prioritize their own pursuit of knowledge over the needs of the organization and their direct reports." Expert 2: "When problem-solving with others in the company, my opinion tends to be the correct one." Which Leader Are You? So, which action logics above felt like you? Think about each sentence for a moment ... now, check out which of the seven leadership styles you embrace on the right based on the sentences you resonated with on the left.

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ACTION LOGIC SENTENCE Strategist 3 Opportunist 1, Opportunist 2, Expert 1, Expert 2 Diplomat 2, Diplomat 3, Expert 1 Strategist 1, Strategist 2, Alchemist 3 Individualist 1, Individualist 2, Individualist 3, Alchemist 1, Alchemist 2 Diplomat 3 Diplomat 1

LEADERSHIP STYLE Democratic Autocratic Laissez-Faire Strategic Transformational Transactional Bureaucratic

The more action logics you agreed with, the more likely you practice a mix of leadership styles. For example, if you agreed with everything the strategist said, this would make you a 66% strategic leader and 33% democratic leader. If you agreed with just the third statement, but also everything the alchemist said, this would make you a 50% transformational, 25% strategic, and 25% democratic leader. Keep in mind that these action logics are considered developmental stages, not fixed attributes — most leaders will progress through multiple types of leadership throughout their careers. Know Your Leadership Style to Become a Better Leader Knowing your leadership style can put you on the path to become a more effective leader. Whether you manage a big or small team, your style heavily impacts how your direct reports see you and how effectively your team works together to achieve your company's goals.

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Volume 8, Number 1, 2022

How to Develop a Project Management Plan: 12 Steps to Success The Project Management Institute’s 2020 Pulse of the Profession report reveals that 11.4 percent of business investment is wasted due to poor project performance. Today’s organizations must uncover the cause of these failures and determine what project management professionals can do to help overcome these challenges. “For decades, we’ve been trying to improve the rate of project success,” says Northeastern University assistant teaching professor Jacques Alexis. “Poor planning has been one of the consistent causes of failure. Often this means the project management team did not engage stakeholders in the planning and therefore didn’t understand the scope of the project. If you don’t understand the scope of the project, then the schedule and the budget will be unrealistic. There is ample evidence that planning is a critical success factor in project management.” By Shayna Joubert | January 11, 2021. https://www.northeastern.edu/graduate/blog/developing-project-management-plan/

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How to Create a Realistic Project Plan in 12 Steps Alexis is a scholar-practitioner with a unique combination of expertise in business economics, general management, portfolio, project, and operations management. He has nearly two decades of experience managing major programs and projects within the manufacturing and power generation industries. Based on his experience, he recommends project managers follow the below steps to develop a plan that results in quality deliverables on time and within budget. 1. Collect requirements from key stakeholders. Once you’ve created a project charter and identified key project stakeholders, it’s essential to gather requirements. “You need input to generate output,” Alexis says. “The planning process starts with collecting requirements from stakeholders. Once you have this information, you will be able to define the scope of the project and determine exactly what you need to deliver to your stakeholders. Strong communication skills are critical at this stage in the planning process. Without effective communication, it’s possible to miss important details that could be detrimental to the project’s overall success. 2. Define the scope of the project. Ask yourself: “What is it the team needs to produce or deliver?” and “What problems are the stakeholders trying to solve?” Then, work with your stakeholders to develop a comprehensive description of the project and the product deliverables in the form of a project scope statement. You must have a clear understanding of the boundaries of the project. For example, if you are building a software app for a customer, you must know what will be included in the app and what won’t. Who will use the application? What is it intended to do? What are the critical functions and features it needs to have? 3. Create a work breakdown structure. Break down the project’s scope into smaller, more manageable deliverables and groups of related tasks, also known as “work packages.” This will allow you to assign resources to different parts of the project based on the skills needed. The work breakdown structure facilitates planning and coordination, which are two important functions of project management. 4. Define project activities. Break down work packages into a list of project activities. Consider this an action plan. It can help to ask yourself: “What are the activities that must be performed to create the deliverables of the project?” 5. Sequence project activities. “Almost everything happens in a sequence, but the trick is to do as many things in parallel as possible—if you have the resources to do so,” Alexis says. “One of the key reasons for adopting formal project management methodologies is to reduce time-to-market. In dynamic and hyper-competitive industries, the ability to reduce cycle time is a competitive advantage.” 6. Estimate activity duration, costs, and resources. The cost, duration, and resources required to complete the project activities depend on the scope of the project. Proper estimating is important for any project, as it helps determine if the plan is viable, set expectations, and keep costs under control. 7. Assign resources to work packages and activities according to skills and interests. Resources include not only labor but also materials, equipment, space, and technology. After identifying which resources you’ll need, Alexis suggests identifying the skill level needed for each activity. “The scope and level of complexity of the project will help you determine in what areas you need to bring in high, mid-level, or entry-level skills,” Alexis says. This step allows you to determine the sequence of events that need to take place. To establish a realistic timeline, you’ll need to know how long each activity will take, how much each will cost, what resources (team members) you’ll need, and also when those resources are available (e.g., check into vacation schedules to avoid unexpected delays).

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8. Build in contingencies. “A plan without contingency is a bad plan,” Alexis says. “Projects rarely go as planned, so you need to build in backup plans. The contingencies can be determined by looking at historical data to identify risks that occurred on similar projects in the past.” For example, if a vendor you’re relying on to deliver a key component of your project has had performance issues in the past, this could impact your schedule. If so, a contingency plan—such as identifying alternative vendors and estimating the costs if this risk should occur—is necessary. The key here is to consider both internal and external factors that may impact your project’s objectives. There are many factors outside of the organization that could add risk to the project, including the consumer price index, the economy, government issues (e.g., emerging regulations), and competitors’ actions. Also, consider organizational culture when formulating your contingencies. The culture of the organization can impact certain elements of a project plan. For example, in some organizations, it’s common to pad estimates, while in others, there is an expectation that a project will have exact numbers. 9. Create a performance measurement baseline. Develop an integrated scope-schedule-cost baseline for the project work, which will serve as a control tool for your project. Then, compare the execution of the project to your baseline to measure and manage performance. These baselines can be established through status reports within project management software applications. “Performance should be measured throughout the project lifecycle,” Alexis explains. “This way, you can identify issues and take corrective action before it’s too late. It’s equally important to measure performance upon completion of the project. This allows you to compare actual results to their baselines to evaluate overall and individual performance.” 10. Develop all subsidiary plans. “Developing a comprehensive and realistic project plan requires time and effort,” Alexis says. “However, planning can make your life easier during the execution phase of the project by preventing nasty surprises and misunderstandings.” Most project plans need to incorporate the following subsidiary plans: x x x x x x x x x x x x

Scope management plan Schedule management plan Cost management plan Quality management plan Resource management plan Communications management plan Risk management plan Procurement management plan Stakeholder engagement plan Requirements management plan Change management plan Configuration management plan

11. Document everything. Document a project plan that outlines the scope, schedule, and cost of the project. Typically, plans should cover cost management, quality management, resource management, communication management, risk management, procurement processes, as well as ongoing stakeholder engagement (i.e., how to continually engage stakeholders through the lifecycle of the project.) 12. Build a knowledge base. Some organizations have a learning culture where project managers are expected to document and share their plans. This can be a valuable way to learn from the mistakes and successes of others. In other companies where this historical knowledge isn’t documented, this could be more challenging, and it may be necessary to reach out directly to other project managers to gain insights.

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Article 11 – Project Management

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FROM THE PUBLISHERS OF PA APER TECHNOLOGY®

Volume 8, Number 1, 2022

Advancing in Project Management Project management is a growing and in-demand career, but how do you take steps to grow in your role? Alexis recommends taking the following steps to further your project management career. Make learning a daily habit. “Some of the most successful project managers I know regularly work on furthering their communication, team building, and negotiation skills,” he says. Remember that learning is everywhere. Earning a degree is an important way to propel your career forward. You can also learn in other ways—from experience on the job and through support systems within the profession. To demonstrate your skills to employers, you can also explore opportunities to earn various credentials, such as becoming a certified project manager. Data has shown that project managers who hold a certification and/or a master’s degree in project management typically earn higher salaries than their counterparts who do not. Develop your technical skills. Like many fields, project management technology is continually evolving, so professionals need to stay ahead of trends in the field. For example, many project managers today are investigating the potential applications of artificial intelligence and robotics. “Artificial intelligence will play an important role in the way we collect, store, and share lessons learned in project management,” Alexis says. “Capturing lessons learned will be more structured, and machine learning will help reduce mistakes and project failure.” Develop a strong network for support. Many professionals are willing to share their knowledge and experience. Two places to start are the Project Management Institute and project management groups on LinkedIn. Hone your leadership skills. Power and influence are important, yet often project managers have project team members on their project who are not their direct reports, which can be an added challenge. However, you can influence people based on your power, which comes from different sources. Sometimes project managers will rely on their expert power to influence team members or their referent power—their ability to connect with others and develop connections within the organization. Simply knowing your field isn’t enough. Strong leadership and communication are essential skills for project managers. Share the value of project management. Demonstrate to managers and others in the organization how project management is essential for developing the organization’s competitive advantage. Effective project management can result in measurable benefits such as improved productivity or reduced time-to-market for a new product.

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Article 11 – Project Management

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

8 Key Meeting Etiquette Rules for Professionals Business meeting etiquette is a standard of behaviour that is expected while you are in the office or in meetings. Maintaining a high standard of professionalism and respect is the essence of business etiquette and meeting etiquette. Behaviours such as being on time, being off your phone for the entirety of the meeting, providing a detailed meeting agenda, making introductions and listening without interruption are all important meeting etiquette rules. While these kinds of rules might not be necessary for more informal discussions, it’s good to keep this set of business manners in mind for more formal interactions, especially when you don’t know everyone in the room. This article covers the following: 1. Why is meeting etiquette important in business? 2. Meeting Etiquette Rules to Remember By Kate Dagher (06/25/2021) 7 minute read. https://fellow.app/blog/meetings/meeting-etiquette-rules/

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Article 12 – Meeting Etiquette

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FROM THE PUBLISHERS OF PA APER TECHNOLOGY®

Volume 8, Number 1, 2022

Why is meeting etiquette important in business? Meeting etiquette is really important for several reasons. First, it improves communication between you and your team if everyone is adhering and respecting certain manners at work and in meetings. This standard of communication encourages an environment where every person respects one another, everyone is heard and everyone feels comfortable sharing their thoughts. Meeting etiquette also promotes higher productivity because central to these etiquette rules are coming prepared, being organized, listening, and taking turns speaking. This means the time is being optimized the most effectively. Lastly, it improves relationships within the working group because when people feel respected, it also enhances trust which strengthens those business relationships. 8 Meeting Etiquette Rules to Remember 1. Be punctual 2. Come prepared 3. Speak clearly 4. Actively listen and participate 5. Give others the opportunity to speak 6. Follow the agenda 7. Ask clarifying questions 8. Be attentive to your body language 1 Be punctual Being punctual is one of the most important business etiquette rules. It shows professionalism, respect and proper preparation. It’s common courtesy for the rest of the group to get to the meeting on time so that you’re respectful of other people’s time. When leaders tolerate lateness, it means that people may begin to take advantage of that. Most people will not and should not wait for you to arrive at the meeting if you’re late. Simply put, it looks bad! It’s unprofessional so it’s best to be in the meeting in advance so that you have some time to sit down and prepare for the discussion ahead. 2 Come prepared Make sure that your meeting agenda is sent far in advance, with time for the group to collaborate and make suggestions for items to add. If there is any kind of documentation that was sent with the meeting invite, be sure to brief yourself and familiarize yourself with the content so that you can actively participate. Make sure to write down any kinds of questions you have or topics you’d like to bring up before the meeting happens so that these things don’t slip your mind. If you’ve been asked to prepare anything ahead, make sure that it is accounted for so that you can feel confident and prepared. 3 Speak clearly It’s so important to speak loudly enough and clearly enough so that everyone can understand. Millennials and Gen Z tend to speak really quickly, so if this is you, slow it down to a pace that is easily understood by all. Speaking loudly and clearly portrays confidence and professionalism. If you’re a soft speaker, be sure to work on this point as quiet speakers often struggle to come off as assertive and sure of themselves (even when they are!). Speaking clearly is going to contribute to the meeting’s productivity because everything will be well understood and nothing will have to be repeated. 4 Actively listen and participate Find a good balance between actively listening and also participating in the discussions taking place. A good rule of thumb is to listen at least twice as much as you speak, especially when there are a lot of people in the room. A few ways to show the speaker that you are actively listening is through non-verbal communication, such as nodding your head, writing notes, asking questions or contributing comments. When you engage in these actions, it’s actually going to help keep your attention so that you can listen more effectively and you’ll get more out of the meeting. Active listening means that when it’s your turn to participate you won’t repeat what has already been discussed and you can bring fresh insights, opinions and contributions to the table. 5 Give others the opportunity to speak No one enjoys a meeting where one or two people dominate the entire conversation – in that case, what’s the point in it being a team meeting? Give others the opportunity to speak and if you’ve just spoken, take some time to actively listen to others. Be patient in waiting for your turn to speak and look for the right cues to contribute to the conversation. A good time to contribute is when you’re a subject matter expert on the topic when you have updates and when the conversation trails off. Write down any points that come up while others are speaking so that you can revisit your list and determine if they’re worth bringing up. Page 2 of 3

Article 12 – Meeting Etiquette

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FROM THE PUBLISHERS OF PA APER TECHNOLOGY®

Volume 8, Number 1, 2022

6 Follow the agenda Do not stray from the meeting agenda. Staying on topic is good meeting etiquette because it respects the time and effort that has gone into organizing the meeting and the topics that will be covered. Now is not the time to bring up other things that are not listed to speak about. This is going to save time and make your discussion more productive. If you notice you’ve drifted off-topic, take note of what it was and bring the conversation back to its main purpose. You can always revisit these side discussions at a later time with the people who are directly involved. 7 Ask clarifying questions Asking clarifying questions is good business meeting etiquette because it shows that you are listening and that you want to properly understand what has been discussed. That said, make sure that you are asking questions at the appropriate time. When your question is relevant to what is being discussed, before the speaker or facilitator moves on to the next topic, that’s the right time to ask. A good facilitator will ask if there are any questions periodically but if that’s not the case, don’t be shy to clarify what’s been discussed because you will get a lot more out of the meeting when you fully understand what is being spoken about. Avoid asking all of your questions at the end of the meeting because this can be time-consuming, especially if you’ve got a list. Think about speaking to the appropriate person privately or shooting them an email. 8 Be attentive to your body language It’s important to be self-aware of your own habits and body language during meetings. It’s natural to become restless or bored, especially during long meetings. That said, it’s important to avoid things such as tapping or clicking your pen, fidgeting with your clothes, jewelry, or notebook, swiveling your chair or playing with different heights, tapping your feet, rustling papers, making quiet noises or humming, and last but not least, do NOT pull out your cell phone. Turn off or silence your device and put it away somewhere that it’s no longer visible, such as in your purse, briefcase, or jacket pocket. If you want to bring your laptop along, ask the facilitator or meeting organizer beforehand if it’s appropriate. While you may think these actions are harmless, they are often seen as rude and disrespectful. A good way to keep your focus is to write notes, actively write down questions that you would like to ask and to participate in the meeting. Parting advice It can be tough to understand what’s appropriate and what’s not during meetings because company cultures differ so much. That said, being respectful and punctual are universal business etiquette rules that should always be followed. Meeting etiquette rules hold you to a high standard of behaving appropriately and in a way that is also matched by your team and colleagues. Remember to always be early or on time, to come prepared and to speak loudly and clearly enough. Actively listen more than you participate so that you give everyone the chance to speak and do not deviate or stray from the meeting agenda- you can bring up any side conversations at a later time. Ask some clarifying questions to ensure you’ve understood the full context and be aware of your own body language and the way you are conducting yourself during the meeting. We hope that this article has been helpful in laying down some universal meeting etiquette rules. If you found it helpful, be sure to share it with a friend or a colleague. Until next time, it was great to see you again!

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Article 12 – Meeting Etiquette

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Products & Services & News PITA CORPORATE SUPPLIER MEMBERS Page 2 ABB Fast Online Moisture Sensor Page 4 ABB L&W Sample Cutter Page 5 Archroma Cartaseal Food Packaging Barrier Coating Page 7 Buckman Ackumen™ Connected Reality Page 8 Valmet Fiber Furnish Control

PITA NON-CORPORATE SUPPLIER MEMBERS Page 9 Voith Edgesaver – Edge Trim Page 10 Voith QualiFlex QView Press Sleeve Page 11 Voith InduraClean (IDC) Cleaning System

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Volume 8, Number 1, 2022

ABB LAUNCHES FASTEST PAPER MACHINE MOISTURE SENSOR ON THE MARKET, TAKING 5,000 MEASUREMENTS PER SECOND ABB has released its High-Performance Infrared-Reflection (HPIR-R) moisture sensor, which provides the fastest, most precise moisture monitoring available on the market today. Taking up to 5,000 measurements per second, the sensor delivers precise, high-resolution measurement that enables mills to increase throughput while reducing operating costs. This advanced, patented technology will help pulp, paper and board producers to always know the precise moisture levels, giving them confidence to raise moisture targets and improve their CD profiles, enhancing end product quality with fewer rejects as a result. Being able to measure and control the moisture levels as the sheet moves through the paper machine is critical to reducing energy requirements. This leads to optimised drying, decreased steam usage, significant energy savings in dryer sections and reduced carbon emissions. In fact, changing the steam pressure to create a moisture change of just 1% can equate to $400K in energy savings. The small spot of infrared energy used in the sensor provides excellent streak resolution and accurate edge-to-edge sheet measurement, even in the most difficult environments. Measurement while scanning is continuous, with no beam chopping or filter wheels ensuring optimum signal-to-noise ratio and maximum measurement rate. ABB’s new HPIR-R moisture measurement, which also has a built-in sheet temperature sensor, is designed to be fully air-cooled and field repairable. That, coupled with its insensitivity to dust and disturbances enables high uptime and lower total cost of ownership than similar solutions. “Unlike competitive offerings, ABB’s HPIR-R moisture sensor provides the highest frequency measurements possible, which helps customers to improve quality, reduce downtime, decrease costs and increase yields,” said Andy Broomfield, Product Line Manager at ABB. “It has been designed for papermakers looking for accurate and precise moisture measurement in hot, difficult machine environments.” While it can be placed in any location, the highest impact application for this reflection moisture sensor is before a size press, where better precision and accuracy let you raise the moisture target, giving optimised starch/sizing pickup and reduced drying energy demand. This also applies to pre-coat locations. Another high-value application is placing it after the wet press section, enabling operators to adjust press loadings to improve the moisture profile and increase sheet dryness going into the dryers. In addition to energy savings, this also gives higher sheet strength in that sensitive area of the machine, meaning improved runnability and sheet break recovery. Part of the ABB Ability™ Quality Management System, the sensor is fully digital with highspeed measurements provided alongside a rich set of diagnostic data which is ideal for analytics to inform on-site or corporate-level decision-making. It is applicable for all network platform types and can be used to measure publication grades, graphic papers, board, tissue, packaging, specialist and recycled grades.

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Volume 8, Number 1, 2022

ABB (ABBN: SIX Swiss Ex) is a leading global technology company that energises the transformation of society and industry to achieve a more productive, sustainable future. By connecting software to its electrification, robotics, automation and motion portfolio, ABB pushes the boundaries of technology to drive performance to new levels. With a history of excellence stretching back more than 130 years, ABB’s success is driven by about 105,000 talented employees in over 100 countries. www.abb.com ABB’s Process Automation business is a leader in automation, electrification and digitalisation for the process and hybrid industries. We serve our customers with a broad portfolio of products, systems, and end-to-end solutions, including our # 1 distributed control system, software, and lifecycle services, industry-specific products as well as measurement and analytics, marine and turbocharging offerings. As the global #2 in the market, we build on our deep domain expertise, diverse team and global footprint, and are dedicated to helping our customers increase competitiveness, improve their return on investment and run safe, smart, and sustainable operations. go.abb/processautomation ǣȀȀ Ǥ Ǥ Ȁ Ȁ Ȁͺ͸͹ͳͷȀ Ǧ Ǧ Ǧ Ǧ Ǧ Ǧ Ǧ Ǧ Ǧ Ǧ ǦͷͲͲͲǦ Ǧ Ǧ

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Volume 8, Number 1, 2022

ABB RELEASES NEW L&W SAMPLE CUTTER ABB is expanding their portfolio and has released their new L&W Sample Cutter, a new device for sample preparation that can be used with two of their laboratory testing devices, the Tearing Tester and Bending Tester. It can also be used with the L&W Autoline Elrepho Module. The L&W Sample Cutter is a triple shear, manually operated cutting tool for easy and quick preparation of accurate and precise test pieces for use in tearing, bending resistance and folding strength tests. The punch and die are made of sturdy tempered tool steel to ensure precision cutting, essential for reliable testing across a wide range of paper grades and grammages. Operation is simple, with the samples needing to be correctly placed in the machine and cross-machine directions aligned with the back stop within the cutter. The ergonomic design and slanting edges of the punch ensure that only slight to moderate force is needed to cut the test pieces. The cut test pieces slide towards the operator automatically for quick and safe collection of the test pieces. Furthermore, there is a safety device around the punch to protect the operator from hand or finger injuries.

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Volume 8, Number 1, 2022

ARCHROMA LAUNCHES NEW PFC-FREE* AND AMMONIA-FREE* CARTASEAL® VWAF BARRIER FOR ODORLESS PAPER-BASED FOOD PACKAGING Archroma, a global leader in specialty chemicals towards sustainable solutions, announced the launch of Cartaseal® VWAF, a new industry-leading perfluorinated compound (PFC)free* and ammonia-free* barrier coating for odour-free packaging applications. Archroma is well known for its innovations and sustainable solution systems aimed at helping packaging & paper manufacturers to optimise productivity and/or create value in their markets. The multifunctional Cartaseal® range offers barrier solutions that can be used to protect from grease, oils, water and water vapor in both packaging and food packaging applications such as pizza boxes, sandwich wedges, fresh vegetables, fast food service and general supermarket packaging. The latest addition to the range is the new Cartaseal® VWAF, which has been developed in line with the principles of “The Archroma Way to a sustainable world: safe, efficient, enhanced, it’s our nature”. The innovative Cartaseal® VWAF is designed to form a continuous and defect-free film-like coating on the paper surface. The resulting barrier offers class-leading performance against the penetration of oils, fats, water and vapour. The odour-free product is also ideally suited to food packaging applications, where the taste and smell of the packed food can be very sensitive to the environment and must be carefully preserved for the full enjoyment of the consumer. Thanks to its superior performance, Cartaseal® VWAF can be used as a more sustainable alternative to replace not only PFC-based coatings but also plastic in applications where resistance to water, oil and fats and water vapour condensation is required. Developed with food packaging in mind, Cartaseal® VWAF is compliant with FDA and BfR requirements for food contact applications. It is also compliant with, eco-labels such as EU Flower, Nordic Swan and several annexes of Blue Angel, and is of course REACH registered. Importantly, Cartaseal® VWAF offers increased potential for compostability, repulpability and recycling compared to PFC and plastics, since the coating will break down with the paper during the recycling process. Cartaseal® VWAF is at the core of the new PACK IT CLEAN system just launched by Archroma where it is combined with a primer solution for cases where a binder or pre-coat can also be used to further boost performance. The PACK IT CLEAN system can be found in the online Archroma System Selector: https://www.archroma.com/systems "Consumers and regulators are increasingly attentive to how products are made, and rightfully so”, explains Andy Bell, Head of the Competence Center Chemicals at Archroma. “It is our responsibility as an industry to develop and convert to technologies that reduce our impact on the environment and on people's health. That is exactly what we at Archroma do, with innovations like Cartaseal® VWAF. Because it’s our nature." Page 5 of 11

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Volume 8, Number 1, 2022

All systems can be found https://www.archroma.com/systems

the

online

Archroma

*Below the limit of detection according to industry standard test methods

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Products & Services

System

Selector:

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Volume 8, Number 1, 2022

BUCKMAN - ACKUMEN™ CONNECTED REALITY Immersive digital technology provides real solutions fast. Buckman’s expanding Ackumen platform now includes Ackumen Connected Reality. It’s an immersive digital consulting technology that combines artificial, augmented, and mixed reality capabilities. Ackumen Connected Reality enables Buckman personnel and customers to see, collaborate, and solve remotely, dramatically reducing response time, errors, costs, and downtime. Connect with real subject matter experts. Connected Reality allows your on-site Buckman representative to consult with subject matter experts anywhere in the world to resolve, in just hours, issues that may have otherwise taken weeks with an in-person visit. Connected Reality allows experts to see what you see to help answer questions about new applications, equipment configurations and more. Connect with true space planning accuracy. Making room for a new piece of equipment can be challenging, often requiring last minute adjustments after the equipment is delivered. With the mixed reality capabilities of Ackumen Connected Reality, you can leverage 3D models and holograms to make accurate space planning and logistical decisions prior to committing to the purchase or lease. By eliminating last minute surprises, you can save time and money. Connect with timely maintenance solutions. The faster you solve your Maintenance, Repairs & Operations (MRO) issues, the sooner you can be back up and running. Ackumen Connected Reality gives field service technicians documented guidance and access to expert advice via AR technology to troubleshoot and resolve issues faster and reduce downtime. Because there’s no need for subject matter experts on site, you don’t need pull employees from your workforce to provide assistance and support. The difference is real. The results, unreal! If you want the power of real-time support with unprecedented accuracy, efficiency, and vision, connect with your Buckman sales associate and ask for a demo of Ackumen Connected Reality. https://www.buckman.com/smart-technology/ackumen-connected-reality/

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Volume 8, Number 1, 2022

VALMET LAUNCHES INTELLIGENT FIBER FURNISH CONTROL TO SECURE BETTER REFINER OPERATION Valmet introduces the Valmet Fiber Furnish Control application package for board and papermakers to stabilise refiner operation for maximised production efficiency with ensured furnish quality. Based on real time measurements of multiple fibre properties and freeness, the control features advanced feedback and feedforward solutions together with model predictive control. The Valmet Fiber Furnish Control application can be fully integrated into an existing Valmet DNA Automation System or Valmet IQ Quality Control System. The solution is also available as a stand-alone version including all necessary basic licenses and hardware if required. Demonstrated results In the development phase, the control performance of the Valmet Fiber Furnish Control was followed closely for 18 months at a mill in Finland, where the solution ensured that stock production and quality targets were met from two fibre lines, while providing energy savings. In the fibre refining lines, freeness variability was reduced by 30% to almost 70% compared to the time before the control was introduced. “In the one and a half years since the project started, the reduction in web breaks due to the more homogenous fibre furnish resulted of several extra days of production. The best thing was the positive feedback from the operators on how they were able to focus more on controlling the machine when making grade changes,” says Ismo Joensuu, Manager, Board & Paper Analyzers, Automation business line, Valmet. Key fibre properties taken into account Typically, refiner controls have been based on specific energy or freeness targets where key fibre properties such as fibre length, fines, shives and fibrillation are followed. Valmet Fiber Furnish Control can be connected to a Valmet Fiber Furnish Analyzer, which continuously measures these properties in adjusting the specific energy set-point for target freeness. Another key element of the control are Valmet’s consistency measurements which provide reliable and accurate measurements essential for the stabilising control functions. Read more: www.valmet.com/fiber-furnish-control

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Volume 8, Number 1, 2022

VOITH’S NEW EDGE TRIM CONCEPT EDGESAVER ACHIEVES SIGNIFICANT SAVINGS IN VALUABLE VIRGIN FIBERS With the new EdgeSaver edge trim concept, Voith is effectively improving its range of products for stabilising the web edge in the headbox area. The innovative system trims the web edge in the stock jet exiting the headbox. As a result, paper manufacturers not only save valuable raw materials like virgin fibres but also reduce the energy consumption for paper production. In conventional systems, the edge cut on multi-ply machines is only done after couching, so that the mixed trim residues can only be returned to the lower quality stock cycle. By contrast, the innovative design of the EdgeSaver blade offers a simple and energy-efficient solution for adjusting the web edge directly in the headbox jet. Fibres that exceed the required paper web width are not lost in the couch pit, as they are discharged before the suspension reaches the wire. The discharged stock suspension can thus be returned directly to the primary fibre stock cycle in a single-sort process. In addition, the web width can be adjusted to specific customer requirements in the wet end, which offers crucial advantages, above all when producing various paper grades with different run-out widths. As a result, EdgeSaver helps to significantly reduce raw material costs and thus ensures a smaller carbon footprint. “By using the Voith EdgeSaver we consume less energy and therefore reduce our carbon footprint, because the product allows high-quality fibres to be retained. This means, we not only produce more sustainably, but also more cost-efficiently.” - Oliver Kern, Plant Manager at Papier- und Kartonfabrik Varel The EdgeSaver also offers an impressive improvement in paper quality. Thanks to its specially manufactured side shield with a patented, adjustable S-shape, edge waves are minimised. This improves edge stability and also facilitates the successful threading of the web into the press section. The Teflon seal on the underside of the side shield provides an optimal seal to the wire. For the first time, the seal can be adjusted with the machine running. The EdgeSaver can be mounted to the standard headboxes of all manufacturers. It can be easily installed on both sides of the web in just a few hours during a shutdown. Changing the forming fabric is also not a problem, as the ingenious swivel device enables it to be replaced easily without having to restore the optimised settings on the EdgeSaver afterwards. “The EdgeSaver enables us to variably adjust the paper web width without major rebuild measures. Even with changing production parameters, we are able to produce without restrictions, thus reducing breaks and production losses due to defects in the edge area.” Andreas Jaeger, Plant Manager at MM Neuss GmbH https://voith.com/corp-en/newsroom/press-releases/2022-01-31-vp-voiths-new-edge-trimconcept-edgesaver.html

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Volume 8, Number 1, 2022

VOITH’S NEW QUALIFLEX QVIEW PRESS SHUTDOWNS AND INCREASES EFFICIENCY

SLEEVE

REDUCES

UNPLANNED

Web breaks and paper jams are among the rare but real problems in paper production. With each such incident, invisible damage can arise inside the press sleeve. As the latest addition of the QualiFlex family, the QView press sleeve is designed to make inside damage visible and help papermakers take action before severe failures happen. The innovative press sleeve is the predictive maintenance solution for board and packaging paper machines and complements the proven and established portfolio of Voith QualiFlex press sleeves. The advantages of QView are achieved by two unique and novel features. For the first time, dyed lubrication oil and a special-coloured polyurethane are used for the press sleeve. Possible cracks in the press sleeve absorb the dyed oil and, when exposed to UV light, a strong contrast between the intact area with no oil and the damage becomes visible. Due to its special colour, the innovative press sleeve allows the UV light to shine through and makes inspection as well as real predictive maintenance easier. Hence, QView functions as an early warning system and reduces unplanned paper machine shutdowns while increasing efficiency and saving costs. “Not only does the QView press sleeve have an excellent running performance as well as good crack resistance, but it also helps to avoid oil leakage. Combined with the damage detection at an early stage, the QView press sleeve makes the customer’s life much easier and saves resources.” - Christina Bauer, Global Product Manager Press Section & QualiFlex at Voith Paper. https://voith.com/corp-en/news-room/press-releases/2022-02-24-vp-voiths-new-qualiflexqview.html

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g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL®

Volume 8, Number 1, 2022

VOITH - UP TO 50 PERCENT LESS ENERGY CONSUMPTION WITH THE NEW INDURACLEAN HEAVYWEIGHT CLEANING SYSTEM For optimised cleaning, Voith introduces the new InduraClean (IDC) product family as part of its BlueLine stock preparation portfolio. The system consists of an improved cleaner bank, which can be combined with both the new InduraClean IDC-4 and optimised InduraClean IDC-5. Depending on requirements, the focus of the modular cleaning technology can be on significantly increased production, energy reduction of up to 50 percent or vastly improved separation efficiency. “We have already received very good customer feedback, the cleaner installations are running efficiently and smoothly. A quick start-up was ensured by our experts. The results are very satisfying. With the help of the new cleaners, our customers can significantly reduce their energy requirements and minimise fibre losses.” - Stefan Walker, Area Sales Manager at Voith Paper Optimised cleaner bank and new cleaner design The InduraClean IDC-4 combines four individual high-efficiency cleaners to enable high throughput with reduced space requirements. In addition, the cleaner bank features a flowoptimised design that avoids deposits in the cleaner bank due to rejects or heavily loaded grades. Besides the revision of the cleaner connection, the bank has been extended to include an individual isolation. This means that individual cleaners can now be shut down during operation as needed. “With our new InduraClean portfolio, we have developed the most comprehensive cleaner product portfolio in the paper industry. We can offer individual solutions for all customer requirements. The InduraClean IDC-4 has already proven its operational reliability, ease of maintenance and high separation efficiency in a wide variety of installations. Customer reactions to the results and operation have been consistently positive. Even at low pressure differentials, the extremely robust cleaners achieve high separation rates. This allows new circuit concepts and thus high energy savings.” - Thomas Jaschek, Global Product Manager at Voith Suitable design variants for individual customer requirements There are two different versions of the InduraClean IDC-4 type, depending on the objective. The Voith experts designed the InduraClean IDC-4F (FourFlow) for large production capacities, especially for board and packaging papers. Meanwhile, the InduraClean IDC-4Q (FourQuality) is particularly suitable for speciality and graphic paper grades, as here the focus is on very high cleaning efficiency and quality. The new product family also includes the widely used cleaner type HCL 5 – now referred to as InduraClean IDC-5. Unlike the InduraClean IDC-4, it consists of only one cleaner cone. This proven system is also available with different configurations and with the option of lightweight separation. In addition to the installation of the new cleaner banks, Voith also offers the fast rebuild of existing banks. Voith provides support both in system planning and installation as well as commissioning and service for optimum results. The new cleaners can also be integrated into banks from other manufacturers. Find more information here: www.voith.com/cleaning. Page 11 of 11

Products & Services

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

CALENDAR OF EVENTS - 2022 PITA TRAINING COURSES PITA / MCP Maintenance Planning & Scheduling

24-25 May

PITA

Fundamentals of Wastewater Treatment

14-15 Jun.

PITA

Introduction to Wet End Chemistry

9-10 Nov.

PITA / Gernsbach

Fundamentals of Papermaking

6-8 Dec.

INTERNATIONAL CONFERENCES & EXHIBITIONS Paperex, New Delhi, India

10-13 May

Paper & Biorefinery, Graz, Austria

18-19 May

30th International Munich Paper Conference, Germany

23-25 May

PulPaper, Helsinki, Finland

7-9 Jun.

Technologiekring, Apeldoorn, The Netherlands

15-16 Jun.

Zellcheming Conference, Weisbaden, Germany

26-29 Jun.

CPI Health & Safety Conference, Sutton Coldfield, UK

27-28 Jun.

Zellcheming Trade Fayre, Weisbaden, Germany

29 Jun. – 1 Jul.

PRIMA 2022, Amsterdam, The Netherlands (10% off with code PRIMA22PT)

6-7 Sep.

Specialty Papers Europe 2022, Amsterdam, The Netherlands (10% off with code SPEU22PITA)

6-7 Sep.

Tissue & Paper, Bangkok, Thailand

14-16 Sep.

MIAC, Lucca, Italy

12-14 Oct.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 1 Events

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Installations The following pages contain a summary of the various installations and orders from around the world of papermaking, wood panel and saw mills, and bio-power generation, received between the end of November 2021 and end of March 2022.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 6

Installations

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COMPANY, SITE Ahlström-Munksjö Ställdalen AB Sweden Ahlstrom-Munksjö Madisonville Kentucky USA Andhra Paper Ltd. Kadiyam India Anon South-eastern United States Arctic Paper Kostrzyn Poland Arkhangelsk's Pulp and Paper Mill Novodvinsk Russia Biosphere Corporation Ukranian Burgo Group Avezzano Mill Italy Burgo Mosaico Group Tolmezzo Italy CAMA Lallio Italy

SUPPLIER Valmet

ORDER DESCRIPTION IQ quality control system (nonwovens FM2)

URL Valmet 1

Valmet

automation solution (glass fibre line)

Valmet 2

Valmet

new hydraulic headbox (PM3)

Valmet 3

Enerquin

paper machine air systems rebuild Fiber Furnish Analyzer (Valmet MAP Q) with services

Cartiera Pirinoli S.C. Roccavione Italy Cartiera Raipaper Isola Del Liri Frosinone Italy Cascades Bear Island mill Virginia US Crown Paper Mill ICAD Abu Dhabi Doruk Kagit Sanayi ve Ticaret A.S. Turkey Doruk Paper and Packaging Industry Inc. Kayabasi Turkey

Sael

Valmet

oxygen delignification system including additional Valmet TwinRoll presses

Valmet 5

Andritz

spunlace line (nonwovens)

Andritz 1

Andritz

rebuild press section (PM2)

Andritz 2

Sael

rebuilding drive section of PM3

Sael

electrical reconstruction of the wet section control and the reconstruction of the PULPER HD control restoration of Pasaban sheeter

De Iuliis

refurbishment of press section (PM1)

Kemira

selected as primary chemical supplier for new recycled board mill

Valmet

tissue machine

Valmet 6

Runtech

vacuum system rebuild (PM3)

Runtech 1

Runtech

vacuum system rebuild (PM1, 2 & 4)

Runtech 2

Page 2 of 6

Valmet 4

Installations

Kemira

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COMPANY, SITE Essity Menasha Wisconsin USA Giacosa Paper Mill Italy

SUPPLIER Andritz

ORDER DESCRIPTION drying, air and energy technology (PM3 & 4)

Sael

GUTEX Holzfaserplattenwerk Eschbach Germany Henan Xinya New Tech Materials Co.,Ltd. Xianxing City Henan Province China Hitachi Zosen Corp Fukuyama Hiroshima Prefecture Japan HKB-Hoa Lu Paper Joint Stock Company Nho Quan District / Province Vietnam Holmen Iggesund Paperboard Ltd. Workington UK ICT Kostrzyn Mill Poland Infinited Fiber Company Finland

Andritz

drive and automation control system DCS rebuild (PM2) – in collaboration with Andritz who is rebuilding the wet end to supply a second fibre preparation system for the production of insulation board two paper rewinders

INPEL Santo Antônio de Pádua RJ Brazil Intertrade Hellas S.A. Greece Jiangxi Five Star Paper Co., Ltd. China Kemira Äetsä plant Sastamala Finland Kim Tin Group Chon Thanh Binh Phuoc province & Dau Giay Dong Nai province both Vietnam

Hergen

A.Celli

Andritz

URL Andritz 3

Andritz 4

ACelli 1

high-efficiency PowerFluid circulating fluidized bed boiler to biomass-fired power generation facility complete OCC line including reject treatment system

Andritz 5

Andritz

primary effluent and sludge treatment line

Andritz 7

Andritz

two heat recovery chains for tissue production

Andritz 8

AFRY

main engineering partner for new regenerated textile fibre plant new tissue machine (replacement for MP2)

AFRY

Andritz

Andritz 6

Hergen

A.Celli

tissue line from virgin fibre

ACelli 2

Andritz

high-capacity CTMP system

Andritz 9

Valmet

automation solution (chemical plant)

Valmet 7

Dieffenbacher

two MDF plants

Dieffen 1

Page 3 of 6

Installations

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COMPANY, SITE Kıvanç Tekstil Sanayi Ve Ticaret Adana Mill Turkey Kıvanç Tekstil Sanayi Ve Ticaret Adana Mill Turkey

SUPPLIER AFT

Valmet

Klabin “Puma Capacity Increase II” Ortigueira Paraná Brazil Klabin Brazil Liansheng Pulp & Paper Zhangzhou Fujian Province China Lucart Diecimo factory Lucca Italy Mercer Peace River Pulp Mill, Alberta & Mercer Celgar Pulp Mill British Columbia Canada Metsä Board Husum Sweden MG TEC Industry Romania Model Paper Eilenburg Germany

Andritz

Mondi Frantschach Mill Austria

Andritz

MRS Karton Turkey MRS Karton Turkey

Techno Paper

Naini Paper Limited Kashipur Mill India Natron-Hayat Maglaj Bosnia-Hercegovina

Valmet

OCC line, three stock preparation lines, and an OptiConcept M containerboard making line with automation and services modernisation of the cooking, washing, screening and bleaching processes

URL AFT 1

Valmet 8

Andritz 10

Pasaban

two new sheeting machines

Pasaban

Andritz

two tissue machines, including stock preparation equipment

Andritz 11

Enel Group

3MWp photovoltaic power plant

Enel

Valmet

replacement of distributed control systems (DCS)

Valmet 9

Valmet

long-term performance agreement and board machine rebuild (BM1) new tissue line

Valmet 10

paper machine grade conversion with automation (newsprint to lightweight containerboard) two new evaporation units, a secondary surface condenser, new pumps, vapour ducts, and circulation pipes the engineering and furniture for a new winder cabinet, desk, drive and automation with DSC for a new winder new headbox with CD control (PM2)

Valmet 11

Andritz Valmet

Sael

Projet BV

Page 4 of 6

ORDER DESCRIPTION POM system (containerboard)

dryer fabric- and press feltcleaners (PM4)

Installations

Andritz 12

Andritz 13

Techno Sael 5

Valmet 12

Projet 1

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COMPANY, SITE Norske Skog Bruck Austria Oy Essity Finland AB Nokia Finland Papeterie Le Bourray Saint-Mars-La-Brière North West France Papiergarda Arco Trento Italy PF Nonwovens Znojmo Czech Republic PG Bison South Africa Pratt Industries Henderson Kentucky USA PT Mega Surya Eratama Mojokerto Paper Mill Indonesia PT Mega Surya Eratama Mojokerto Paper Mill Indonesia RK-Grand OOO Pitkyaranta Pulp Mill Republic of Karelia Russia Sappi Kirkniemi Mill Lohja Finland Sappi Ngodwana Board Mill South Africa

SUPPLIER Valmet

ORDER DESCRIPTION automation and quality control system (PM3)

URL Valmet 13

Valmet

IQ quality control system (tissue line 9)

Valmet 14

Valmet

Quality control system (TM3)

Valmet 15

Sael

automation and drive rebuilding of a Pizzolato sheeter

Projet

7 power cleaners on 7 different nonwovens manufacturing lines

Siempelkamp

MDF line

AFT

Two POMix stock processors (PM18)

A.Celli

end line solutions for production line PM3 (including Pope reel and rewinder) grade conversion rebuild from newsprint to packaging (PM2)

ACelli 3

Andritz

wood handling plant, including a debarking and chipping line

Andritz 14

BMH Technology

biomass fuel handling system

BMH

AFT

AFT 3

SCA Ortviken Mill Sweden SCA Ortviken Mill Sweden Shanying Paper (Jilin) Co., Ltd. China

PulpEye

POM system (headbox screen for the current approach system, POMp degassing and a POM cascade cleaning system) two DotEye sensors analysers, upgrade three other analysers and rent a CrillEye module microwave consistency measuring unit (CTMP line)

Voith

Valmet

A.Celli

Siempelkamp

headbox, top-former, shoe press, size press, and two rewinders and a core handling system for a new machine

Page 5 of 6

Projet 2

Installations

AFT 2

Voith 1

PulpEye

Valmet 16

ACelli 4

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COMPANY, SITE Sonoco Hartsville Mill SC USA Sonoco Hartsville Mill SC USA Steico Sp. z o.o. Gromadka Poland Stora Enso Skoghall Mill Sweden Suzano Barra do Riacho Mill Brazil Suzano Ribas do Rio Pardo Mato Grosso do Sul Brazil Thang Long Energy Environment Joint Stock Company Bac Ninh province Vietnam Toyo Engineering Corporation Tahara-shi Aichi Prefecture Japan Wanhua Ecoboard Chenzhou Hunan and Leshan Sichuan China VPK Alizay Mill France Zibo Oumu Special Paper Co. Zibo Shandong province China

SUPPLIER A.Celli

ORDER DESCRIPTION two rewinders and automated material handling and packaging system

URL ACelli 5

Bellmer

convert PM10 into Uncoated Recycled Board (URB) machine

Bellmer

Valmet

two second-generation defibrator systems (insulation materials plant) board machine rebuild (BM8)

Valmet 17

Andritz

ash recrystallisation plant for the recovery boilers

Andritz 15

Nouryon

long-term chemicals supplier (new pulp mill)

Valmet

waste-to-energy boiler (energy plant)

Valmet 19

Andritz

circulating fluidised bed boiler (biomass power plant)

Andritz 16

Dieffenbacher

two particleboard lines (for straw-based panels)

Deiffen 2

Valmet

grade conversion rebuild (fine to containerboard)

Valmet 20

A.Celli

paper rewinder

Valmet

Page 6 of 6

Installations

Valmet 18

Nouyron

ACelli 6

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY TE INTERNATIONAL®

Volume 8, Number 1, 2022

Research Articles Most journals and magazines devoted to the paper industry contain a mixture of news, features and some technical articles. Very few contain research items, and even fewer of these are peer-reviewed. This listing contains the most recent articles from three of the remaining specialist English language journals alongside one Korean journal and one Japanese journal, both of which publish original peer-reviewed research: x x x x x

IPPITA JOURNAL (Peer-reviewed and other) JAPAN TAPPI JOURNAL (English abstract only) JOURNAL OF KOREA TAPPI (English abstract only) NORDIC PULP & PAPER RESEARCH JOURNAL TAPPI JOURNAL

Notes: 1. IPPTA JOURNAL seems to have replaced IPPTA PAPYRUS 360° after only 2 editions of the latter, as of late 2021. 2. JAPAN TAPPI JOURNAL is a members-only journal that contains excellent research articles – abstracts are in English but articles are in Japanese. 3. JOURNAL OF KOREA TAPPI is an excellent open-access research journal – abstracts are in English but articles are in Korean.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 5

Research Articles

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL®

Volume 8, Number 1, 2022

IPPTA JOURNAL, Vol.33(2), 2021 1. A Novel Manufacturing Process of Paper Composite using recycled Old Newspaper Sheets and Phenol Formaldehyde Resin 2. Effect of Pulping and Bleaching on Handmade Paper from Jute 3. Environmental and Socio-Economic Impact of Managing Private Forest for Pulp Wood: A Case Study of Kulwalli 4. Review on Production and Application of Integrated Chlorine Dioxide Generator 5. Water Recycling in Pulp & Paper Mill Processes 6. About Paper – Importance and Environmental Implications 7. A Step towards Sustainability: Aqueous Barrier Coatings and Corrugation Boxes 8. Adapting to Changes in Container Board Making & Corrugating with Growing ECommerce 9. Corrugation Trends 10. Flexible Packaging - Future of Indian Packaging Industry 11. Footprint of Paper 12. Future outlook of Barrier Coating 13. Importance of Paper in Our Daily Lives: Role of Minerals in Making Paper More Sustainable 14. Importance of paper in our life 15. Paper and its Significance 16. Paper & Packaging: A Perspective & New Frontiers 17. Paper is made of renewable wood fibre, grown sustainably. It is Eco-friendly. Use it PROUDLY. Recycle it though! 18. Paper: Fostering Friendship with Environment 19. PAPER: Myths & Facts 20. Paper: Our Quintessential Companion 21. Papyrus to Paper (A saga of civilisation) 22. Various Uses of Paper in our Daily Life JAPAN TAPPI JOURNAL, VOL.75(10), OCTOBER 2021 1. Roles of Retention and Drainage Aids in Papermaking Process 2. Tissue Machine Technology of Andritz 3. Latest Technologies and Grade Conversions in Overseas 4. Introducing Inertial Shaking unit Allimand 5. Development of Choi-Suki Kun Series—Challenge of Sheeting Technology for Cellulose Fibers and New Materials 6. “Reactive Polymer” of AXISZ system for Wet-end Optimization 7. PCMC’s Approach to Adapt to Changing Conditions 8. Polyacrylamide-based Pitch Control Agent for Pulp and Papermaking Process (II) JAPAN TAPPI JOURNAL, VOL.75(11), NOVEMBER 2021 1. Report on the 88th Pulp and Paper Research Conference 2. Woody Biomass Refinery by Thermochemical Conversion 3. Miscibility between Cellulose Nanofiber and Polymer EmulsionA Colloidal Science Perspective 4. X-ray Diffraction Analysis of a Trace Amount of Components in Papers Using the High Speed Detector 5. The Effect of Paper Lint on Misfeeding and Its Evaluation Method 6. Wood-Based New Functional Materials “MinerPa®”

Page 2 of 5

Research Articles

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL®

Volume 8, Number 1, 2022

7. 8.

ANDRITZ Cutting-edge Digital Technology for Stable and Safe Recovery Boiler Operation Safety Assessment of Cellulose Nanofibers Obtained from Soda Cooking Bamboo Pulp: Bacterial Reverse Mutation Test, Mouse Lymphoma Thymidine Kinase Assay, Micronucleus Test, and Repeated dose 90-day Oral Toxicity Study in Rats

JAPAN TAPPI JOURNAL, VOL.75(12), DECEMBER 2021 1. A Report of the 28th Environmental Conference 2. From Paper Manufacturing Process to Wastewater Treatment Process Kurita’s Comprehensive Method of Reducing Environmental Load 3. Precautions for Outsourcing Waste Treatment in COVID-19 Infection 4. Fundamentals Knowledge and Visualization of Noise 5. Ammonia Co-firing in Coal-fired Power 6. CCUS Initiatives and Future Policy Direction 7. Internal and External Situations Surrounding the Global Warming Issues and Challenges for Japan JOURNAL OF KOREA TAPPI, Vol.53(6), December 2021 1. Effect of Cellulose-Nanofiber-Controlled Emulsion Size on Skin Delivery by Essence 2. Effect of Enzyme-pretreated Cellulose Nanofiber on the Strength of Coloring Paper Used for the Production of Fruit Bags 3. Effects of Beating Degree on the Properties of Foam-formed SwBKP Sheets 4. Preparation and Characterization of Whey Protein Isolate-based Coating Solutions and Coated Papers with Different Plasticizers 5. A Study on Pulping of Paper Mulberry Bast Fiber Using Deep Eutectic Solvent Based on Resorcinol-Choline Chloride 6. Characteristics of Spent Coffee Grounds Holocellulose-PVA Composite Film 7. A Study on Pulping of Paper Mulberry Bast Fiber Using Zinc Sulfate-Based Deep Eutectic Solvents 8. Development of Membrane Filter for Water Treatment Using Anionic and Cationic Cellulose Nanofibers 9. Effect of Temperature of Tetraethylammonium Hydroxide/Urea/Cellulose Solution on Surface Tension and Cellulose Bead Size 10. Characteristics and Material Analysis on the Drafts of Buddhist Paintings in the Late 19th and the Early 20th Century 11. Synthesis of Di-amine Functionalized Lignin Derivative and Its Removal Ability for Heavy Metal Ions 12. Time Series Characteristics of the Imported Pulp Prices 13. Dry Grinding Efficiency of Zeolite According to the Manipulated Variable 14. A Study on the Fuel Characteristics of Pellets Manufactured by Unused Lignocellulosic Biomass and Hardwood Chips 15. Effect of Paper Preservation by Properties of Lining Starch Adhesives: Adhesion Properties According to Starch Type 16. Accessibility Improvement of Bleached Kraft Pulp by Alkali Treatment 17. Impact of Carboxymethylation Pretreatment on Bleached Rice Hull Nanofiber by Grinding 18. The Evaluation of Recyclability with the Barrier Properties of Paper Based Packaging Material

Page 3 of 5

Research Articles

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL®

Volume 8, Number 1, 2022

19. A Study on the Characteristics of Hanji for Painting According to the Conditions of Surface Treatment Using JOURNAL OF KOREA TAPPI, Vol.54(1), February 2022 1. Application of Fracture Toughness Understanding to Improve Papermaking Runnability 2. Study on Paper Drying Rate Based on Lattice Boltzmann Method 3. Adjustment of Strength and Air Permeation Resistance of Low Basis Weight Paper by Separated Beating 4. Fabrication of Superabsorbent Material from Carboxymethyl Cellulose and Seaweed 5. Development of Biodegradable Cigarette Filter Material from Micro-fibers (Part 2) : Fabrication of Cigarette Filter and its Characteristics NORDIC PULP & PAPER RESEARCH JOURNAL, Vol.36(4), December 2021 1. Chemical pulping: Visualization of multiscale ring formation in a rotary kiln 2. Chemical pulping: Chemical and morphological characterization and pulping of Casuarina equisetifolia 3. Chemical pulping: Effect of polysulfide pulping process on the energy balance of softwood and hardwood kraft pulp mills 4. Bleaching: Assessment of Q(OP)D(PO) bleachability of softwood kraft pulp 5. Mechanical pulping: The effect of process design on refiner pulp quality control performance 6. Paper technology: Carboxylated bleached kraft pulp from maleic anhydride copolymers 7. Paper technology: Sustainable coatings on paper for enhancing barrier properties based on hemicellulose 8. Coating: Fold cracking of coated papers: investigation on automated computeraided visual assessment method 9. Coating: The effect of paper coatings containing biopolymer binder and different natural pigments on printability 10. Nanotechnology: Adsorption of biopolymers onto nanocelluloses for the fabrication of hollow microcapsules 11. Nanotechnology: Facile fabrication of superhydrophobic filter paper with improved durability and water repellency 12. Nanotechnology: Evaluation of mulberry branch waste as raw material for nanocellulose synthesis: effects of the synthesis method on product properties 13. Chemical technology/modifications: Tailoring the physical characteristics of solution blown cellulosic nonwovens by various post-treatments 14. Miscellaneous: Refining pulp for tensile strength 15. Miscellaneous: Application of sequencing batch biofilm reactor (SBBR) to recycled paper mill effluent treatment 16. Miscellaneous: Bar forces in pulp refiners NORDIC PULP & PAPER RESEARCH JOURNAL, Vol.37(1), March 2022 1. Chemical pulping: Evaluation of fines separation from unbleached softwood kraft pulp using microperforated hole screens 2. Chemical pulping: Evaluation of pulp and paper making properties of Caesalpinia decapetela 3. Chemical pulping: Novel bulking technologies for cellulose fibres 4. Mechanical pulping: Interpretation of force profiles in mill-scale LC refining

Page 4 of 5

Research Articles

g PAPERmaking! FROM THE PUBLISHERS OF PAP PER TECHNOLOGY INTERNATIONAL®

Volume 8, Number 1, 2022

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Mechanical pulping: Effects of plate wear on bar forces and fiber properties in a mill scale LC-refiner Paper technology: Research on the physical properties of calcium sulfate whisker and the effects of its addition on paper and its printing performance Paper technology: Preparation and properties of an intelligent adjustable functional paper for organic cultural relics Paper chemistry: Application of DSA to improve strength of thermomechanical pulp blended paper Coating: The influence of pigment modulus on failure resistance of paper barrier coatings Coating: Effect of filler additions on pilot-scale extrusion coating of paperboard with PLA-based blends Packaging: Influence of paper properties on adhesive strength of starch gluing Environmental impact: Interfering elements on determination of hexavalent chromium in paper materials with UV-vis spectrophotometry Nanotechnology: Enhanced mechanical and gas barrier performance of plasticized cellulose nanofibril films Lignin: The preparations of nanoporous carbon with multi-heteroatoms codoping from black liquor powders for supercapacitors Miscellaneous: Hybrid films from plant and bacterial nanocellulose: mechanical and barrier properties. Valorization of different raw materials for films production Miscellaneous: Mass-balance based soft sensor for monitoring ash content at two-ply paperboard manufacturing Miscellaneous: Investigation of the effect of light fastness on the color changes of maps prepared by electrophotographic digital printing Miscellaneous: Bulking of cellulose fibres – a review Miscellaneous: Preparation of O-HACC/HEC-acrylate emulsion and its application in paper protection Miscellaneous: Mineral-filled biopolyester coatings for paperboard packaging materials: barrier, sealability, convertability and biodegradability properties

TAPPI JOURNAL, January 2022 1. Editorial: Looking forward, looking back 2. Web lateral instability caused by nonuniform paper properties 3. Microbial load and proliferation associated with various face mask types and sources during the COVID-19 pandemic 4. Preparing prehydrolyzed kraft dissolving pulp via phosphotungstic acid prehydrolysis from grape branches 5. Application of ATR-IR measurements to predict the deinking efficiency of UVcured inks TAPPI JOURNAL, February 2022 1. Editorial: Innovation: How useful is it? 2. Furnishing autohydrolyzed poplar weakly alkaline P-RC APMP to make lightweight coated base paper 3. Utilization of kraft pulp mill residuals 4. Experiments and visualization of sprays from beer can and turbo liquor nozzles 5. A model black liquor formulation for use in development and evaluation of membranes for concentrating weak black liquor

Page 5 of 5

Research Articles

PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY T INTERNATIONAL®

Volume 8, Number 1 2022

Technical Abstracts The general peer-reviewed scientific and engineering press consists of several thousand journals, conference proceedings and books published annually. In among the multitude of articles, presentations and chapters is a small but select number of items that relate to papermaking, environmental and waste processing, packaging, moulded pulp and wood panel manufacture. The abstracts contained in this report show the most recently published items likely to prove of interest to our readership, arranged as follows:

Page 2

Coating

Page 3

Energy Moulded Pulp

Page 4

Nano-Science

Page 6

Novel Products Packaging Technology

Page 7

Papermaking

Page 8

Pulp

Page 10

Testing

Page 11

Tissue

Page 12

Waste Treatment

Page 14

Wood Panel

Page 1 of 15

Technical Abstracts

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

COATING “Effect of coating pigment type on paper printability with water-based inks”, Arif Ozcan, Sinan Sonmez & Dogan Tutak, Journal of Coatings Technology and Research, (2022) online. Nowadays, the need for papers and cardboards with improved surface properties is increasing with the development of the packaging industry. The improvements made are not only limited to the paper and paper surface, but also environmentalist approaches are exhibited in printing ink. For this purpose, the use of water-based ink tends to become widespread, especially in food packaging. In this study, five different paper coating formulations were prepared using different proportions of precipitated calcium carbonate (PCC) and kaolin pigments. Latex (Acronal S360D) was used as a binder. All prepared coating mixes were applied onto the base paper surface. All coated papers were also subjected to the calendering process. In addition, three different dyestuffs (14, 17, 20%) concentrations of water-based printing inks were prepared. Prints were made by the silk screen printing technique on the calendered-coated papers. The optical and physical properties (roughness, air permeance, paper gloss and printing gloss, contact angle and surface energy) of all papers were measured according to the standards. Paper gloss, print gloss, ΔE00 color differences, contact angles and surface energy measurements were made, and the effects of dye ratio on printing and gloss in water-based inks and coating type suitable for printability were investigated. As a result, papers can be coated and even calendered to achieve better paper surface properties and printability. In the case of printing with water-based inks, better printability properties are obtained by choosing PCC pigmented coated papers. “Effect of filler additions on pilot-scale extrusion coating of paperboard with PLAbased blends”, Karoliina Helanto, Riku Talja, Sai Li & Orlando J. Rojas, Nordic Pulp & Paper Research Journal, (2022) online. We study the incorporation of minerals (talc, kaolin and surface-treated calcium carbonate) in paperboard coatings based on PLA to improve their performance, often limited by the low crystallinity and moderate gas barrier of the polymer. Masterbatches of PLA-based blends mixed with the mineral fillers were melt-blended in a twin-screw extruder and applied as a coating on paperboard in a pilotscale unit operating at velocities up to 140 m/min. Thermal imaging was used during the extrusion coating and the effect of the fillers was investigated as far as processability and their effect on the mechanical performance. A reduction of neck-in and improved adhesion between the coating and the substrate were achieved at intermediate mineral loadings. Excess filler and low coating weight generated pinholes, leading to a reduction of the integrity and mechanical properties of the coatings. Overall, we define the performance window for continuous, pilot-scale coating of paperboard with a biopolyester filled with mineral particles, opening the opportunity to realize operations in industrial settings. “Failure prediction of waterborne barrier coatings during folding”, Yaping Zhu, Douglas Bousfield & William Gramlich, Journal of Coatings Technology and Research, Vol.18, pp.1117-1129 (2021). Adding pigments into waterborne barrier coatings improves barrier properties and cost-effectiveness but increases the risk of crack formation during folding. Crack formation is affected by pigment shape, aspect ratio, and concentration; however, the exact mechanism for these effects is still not well understood. In this work, a systematic model was used to understand the influence of the paper and coating thickness, the latex and pigment modulus, the pigment shape and aspect ratio, and pigment concentration on the failure of waterborne barrier coatings during folding. A finite element method-based model was solved with a commercial package to simulate the folding process. These simulations were compared to experimental results to verify the key parameters that affect coating failure. High paper and coating thickness, pigment loadings, Page 2 of 15

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Volume 8, Number 1, 2022

pigment aspect ratios, and modulus differences between latex and pigment increased the likelihood of failure. Experiments and models using lower modulus spherical plastic pigments were more difficult to fail than coatings made with higher modulus kaolin. The maximum strain for coatings bent to a set curvature was the smallest when the modulus of latex and pigment were similar. The model agreed closely with experimental results for two pigment types at various pigment loadings. ENERGY “An improved forecasting model of short-term electric load of papermaking enterprises for production line optimization”, Changzhi Lai, Yu Wang, Kai Fan, Qilin Cai, Qing Ye, Haoqiang Pang & Xi Wu, Energy, Vol.245, 15 April 2022, 123225. The load forecasting is generally based on historical data extrapolation in most forecasting models, resulting in a poor correlation with the production information and significant application limitations. To improve this, the production information-based backpropagation neural network (BPNN) combined with genetic algorithm (GA) and particle swarm optimization (PSO) hybrid forecasting model was established for a papermaking enterprise with the three-level electric data collected. Based on this, shift electric consumption quotas and air compressor transformation energy-saving predictions were proposed. The results show that when the production management information is included, the average mean absolute percent error (MAPE) of the six forecasting results can be 1.2%, an improvement of 18.3% on average, indicating the high accuracy of our proposed model. The unit energy consumption of paper products can be reduced by 3.26% through management optimization using the proposed shift electric consumption quotas. Under the guidance of energy-saving predictions, the overall power saving rate of the production line after the enterprise reforms the air compressor is 3%. The proposed load-forecasting model and energy optimization methods have high accuracy and practical applicability. MOULDED PULP “Investigation of mechanisms and approaches for improving hydrophobicity of molded pulp biocomposites produced from apple pomace”, Clara V. Lang, Jooyeoun Jung,Taoran & Wang Yanyun Zhao, Food and Bioproducts Processing, Vol.133, May 2022, pp.1-15. Cellulose fiber based molded pulp packaging is a sustainable solution to the persistent plastic crisis. This study utilized apple pomace (AP) as a renewable source of fibers and cardboard fibers (CF) as reinforcement material to create molded pulp biocomposites (boards) at AP:CF ratio of 2:1 in 3% solid pulp. For improving water resistance of pomace board, two approaches were employed: 1) incorporating rhubarb pomace (RP), chitosan, and glycerol into pulp formulation, and 2) applying heat resistant, superhydrophobic coatings on the board surface. In addition, composition, water retention value, and morphology of pomace, cardboard and newspaper fibers were evaluated for understanding their interactions and effect on water retention of fiber pulp and quality of derived boards. Response surface methodology was used to optimize pulp formulations based on high water resistance and low board deformation after drying. The optimum pulp formulation consisted of 26.9% w/w of RP, 0.039% w/v of glycerol, and 15.7% of w/w chitosan in the 3% solid pulp. The superhydrophobic coating further enhanced the water resistance of the board. The developed pomace boards were compostable in soil. This study brought new insights for using pomace as alternative fiber to produce water resistant and compostable packaging for various applications. “Mechanical and Hygroscopic Properties of Molded Pulp Products Using Different Wood-Based Cellulose Fibers”, Claire Dislaire, Bastien Seantier, Marion Muzy & Yves Grohens, Polymers, Vol.13(19), 3225 (2021). With an increasing interest for Page 3 of 15

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Volume 8, Number 1, 2022

molded pulp product (MPP) in the industry, it is important to fully understand how the manufacturing process is different from papermaking. One specific way to differentiate the processes is to compare their resulting products. As the paper industry uses several wood fibers with various pulping processes, it is interesting to compare some of these fibers, to further progress our understanding of the MPP process. In this study, six different wood fibers were used (as received) and analyzed to obtain the sample with the lowest moisture uptake and highest tensile properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and fiber analysis module (MorFi) observations were performed, as well as moisture uptake measurements after sorption and tensile tests. We observed significant differences between the fibers tested. Kraft fibers (bleached softwood kraft pulp (BSKP), bleached hardwood kraft pulp (BHKP), and unbleached softwood kraft pulp (USKP)) showed smoother surfaces and less non-cellulosic molecules, such as hemicellulose, lignin, and pectin, in the SEM images. Bleached chemithermomechanial pulp (BCTMP) and recycled pulps (R-NPM and R-CBB) both showed non-cellulosic molecules and rougher surfaces. These results were confirmed with the FTIR analysis. With kraft fibers, MPP mechanical properties were lower than non-kraft fibers. Resulting moisture uptake is in between the recycled fibers (lowest moisture uptake) and BCTMP (highest moisture uptake). The removal of non-cellulosic molecules reduces the mechanical properties of the resulting MPP. The incorporation of non-wood molecules, as found in recycled fibers, also reduces the mechanical properties, as well as moisture uptake, when compared with BCTMP. “Tailoring nanofibrillated cellulose through sonication and its potential use in molded pulp packaging”, Supattra Klayya, Nattaya Tawichai, Uraiwan Intatha, , Han Zhang, Emiliano Bilotti & Nattakan Soykeabkaew, Nanocomposites, Vol.7(1), (2021). Nanofibrillated cellulose (NFC) was systematically tailored by ultrasonic-assisted esterification with lactic acid at different amplitudes and times, which led to modified NFC (mNFC) with different degrees of substitution (DS), between 0.21 and 0.55, as confirmed by titration, FTIR, and C13 NMR. A partial fragmentation and decrease in crystallinity of mNFC were revealed by TEM and XRD. To form molded pulp sheets, 5 wt% mNFC was added into a bagasse (BG) pulp slurry, then partially dewatered before hot-pressed. mNFC worked effectively as self-retention aid, partly solving the issue of drainage during sheet forming as commonly observed from unmodified NFC. The BG/mNFC (DS 0.55) sheet exhibited an enhancement in tensile properties. Water resistance and barrier performance of the current sheets were also evidently increased. The results suggested that the higher DS on mNFC can improve water resistance and mechanical properties, simultaneously overcoming drainage challenges in processing of molded pulp products. NANO-SCIENCE “Techno-economic and environmental evaluation of a market pulp reinforced with micro-/nanofibers as a strengthening agent in packaging paper”, Ferran SerraParareda, Roberto Aguado, Sergi Arfelis, Ramon Xifré, Pere Fullana-i-Palmer & Marc Delgado-Aguilar, Journal of Cleaner Production, Vol.347, 1 May 2022, 131265. Partly inspired by the concept of masterbatch in plastics manufacturing, we developed a strategy to improve the technical viability, the economic feasibility, and the environmental performance of lignocellulosic micro-/nanofibers. Instead of investing strenuous efforts in dewatering and/or drying nanocellulose suspensions to maximize their consistency without significantly hampering redispersion, which still stands as an unresolved challenge, we used them in high proportions (up to 50 wt%) to reinforce a high-yield pulp. The suspension can be dewatered-pressed (0.70–1.75 MPa) to obtain wet laps of never-dried reinforced pulps, or dried to consistencies over 90% to produce dry boards, but at the cost Page 4 of 15

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Volume 8, Number 1, 2022

of lower strengthening capability. In any case, both wet and dry reinforced boards succeeded in enhancing the breaking length of a recycled pulp by up to 62% and 56%, respectively. In light of these results, we proposed a tentative upscaling and subsequent assessment of the process, evaluating different scenarios. From the technical point of view, reinforced pulp boards are much easier to handle and to deliver than dilute aqueous suspensions. In economic terms, savings in transportation costs are worth remarking. Last but not least, this strategy fulfills at least three goals associated with the concept of cleaner production: water recovery (internal recycling), lower CO 2 emissions (especially if transportation takes place by road), and avoiding hazardous chemicals such as hypochlorite. “A high-stable soybean-oil-based epoxy acrylate emulsion stabilized by silanized nanocrystalline cellulose as a sustainable paper coating for enhanced water vapor barrier”, Xuwang Tian, Min Wu, Zhiwei Wang, Jian Zhang & Peng Lu, Journal of Colloid and Interface Science, Vol.610, 15 March 2022, pp.1043-1056. Soybean-oilbased polymer is a promising bio-based water barrier coating on paper packaging but the application is challenged due to its poor water dispersibility. In this present study, 3aminopropyltriethoxysilane (APTES) modified nanocrystalline cellulose (NCC) was used to implement a stable dispersion of acrylated epoxidized soybean oil (AESO) in water and thus synergistically improved the water vapor barrier properties after coating on paper. APTES-NCC was successfully prepared, and displayed a better interface compatibility with AESO through the Michael addition reaction. Compared with NCC, APTES-NCC displayed an improved hydrophobicity and wettability with AESO, with an increase of contact angle from 38.0° to 76.4°, and a decrease of interfacial tension from 91.5 ± 3.5 mN/m to 82.9 ± 1.8 mN/m. As an emulsifier, APTES-NCC can be more effectively adsorbed on the oil– water interface to form a more stable emulsion than NCC, with a decrease of AESO droplets size from 4.8 μm to 3.1 μm, and a remarkable improvement in static and centrifugal stability. In rheological measurement, the APTES-NCC/AESO emulsion showed a wider linear viscoelastic region (3.4%), better viscoelasticity and thermal curing properties than that of NCC/AESO emulsion, which further explained that the stability of APTES-NCC/AESO emulsion were improved. Therefore, APTES-NCC/AESO emulsion as a coating on paper cured into a continuous barrier film can effectively improve the water vapor barrier properties of paper, and the water vapor transmission rate (WVTR) of paper can be reduced from 1392.8 g/m2•24 h (NCC/AESO emulsion-coated) to 1286.3 g/m2 24 h (APTES-NCC/AESO emulsion-coated), both are significantly lower than that of base paper (1926.7 g/m2•24 h). CLSM testing showed that APTES-NCC could interact effectively with AESO to forming a tight barrier on paper surface and at the same time, sealing the pores inside the paper to resist water vapor penetration. The high-stable AESO emulsion prepared by APTES-NCC is expected to facilitate the utilization of NCC and AESO as a value-added material in making sustainable barrier packaging. “Printability of variative nanocellulose derived papers”, Arif Ozcan, Ayhan Tozluoglu, Emine Arman Kandirmaz, Ahmet Tutus & Hakan Fidan, Cellulose, Vol.28, pp.5019-5031, (2021). The printability properties of the paper can be increased by some processes applied to the surface. The use of non-recyclable materials derived from petroleum is decreasing day by day, and the demand for recyclable materials obtained from renewable sources is increasing. These materials include cellulose derivatives, starch types and polyvinyl alcohol. The materials ratios, sizes, physical and chemical properties of these materials used in the processes applied to the paper and the content of the paper will affect the strength of the paper as well as change the surface properties and significantly affect the printability. The aim of this study is to obtain better printability Page 5 of 15

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Volume 8, Number 1, 2022

properties by improving the paper surface with CNF/CNF-OX coating. In this study, fluting and core board papers coated with different amounts of cellulose nanofiber (CNF)/cellulose nanofiber-oxidized (CNF-OX) were produced. Surface properties, contact angle, surface energy, color and gloss of the produced papers were measured by optical microscope, goniometer, spectrophotometer and glossmeter. The papers were printed with the IGT C1 offset printability tester. As a result, in terms of printability, it was determined that CNF/CNF-OX coated papers have smoother surfaces and give better results in terms of both gloss properties and printability. NOVEL PRODUCTS “Development of a Multifunctional Wet Laid Nonwoven from Marine Waste Posidonia oceanica Technical Fiber and CMC Binder”, Saoussen Zannen, Mohamed Taher Halimi, Mohamed Ben Hassen, Emad Hashim Abualsauod, & Asem Majed Othman, Polymers, Vol.14(5), (2022). A Posidonia oceanica waste marine plant was used to produce a wet-laid nonwoven web for multifunction applications. To study the effect of some parameters related to the web characteristics (sheet weight, binder ratio, and pulp ratio) on the mechanical and physical properties of the web, we used a Box– Behnken design plan with three levels. The diagram of the superposed contours graphic method was used to find the optimum parameters of the process for the application of the Posidonia nonwoven fiber on an insulation field. With the measurement of the thermal conductivity properties using the box method, the results demonstrated that the nonwoven fiber from Posidonia oceanica marine waste had good insulation properties in comparison with other classical natural fibers (hemp, flax) used in the field of insulation with the big advantage of being a natural product. PACKAGING TECHNOLOGY “Mineral-filled biopolyester coatings for paperboard packaging materials: barrier, sealability, convertability and biodegradability properties”, Karoliina Helanto, Riku Talja & Orlando J. Rojas, Nordic Pulp & Paper Research Journal, (2022) online. Changing trends in packaging materials has been driven by increasing environmental awareness as well as legislation. In this context, paperboard-based packaging have become increasingly popular due to its bio-based origin, potential biodegradability and physical properties. However, conventional systems lack behind in barrier performance and heat sealability. Hence, the addition of functional layers have been considered as alternative solutions to this challenge. Here we propose a biodegradable PLA-based polymer coating filled with minerals (0–10 wt% loading), namely, talc, kaolin and calcium carbonate, all of which were used in surface application on uncoated folding box board. For this purpose, we used a pilot-scale extrusion unit that produced materials that were tested for key properties. We found that the presence of filler in the PLA layer improved both water vapor (up to 16 %) and oxygen (up to 56 %) barrier properties. Moreover, the main effect of the fillers was observed in heat sealability, which was improved via adhesion at low temperatures, resulting in full fiber tear. Cup forming was less effected by filler loading in the PLA coating while repulping tests indicated the presence of large flakes of the polymer coating in 1 %-consistency slurries. Finally, biodegradability was slightly delayed in filler-containing samples (biodegradation within 10–60 days), most likely due to the nucleating effect of the fillers. Nevertheless, all the samples can be classified as biodegradable. Overall, our results represent a step forward in scale-up adoption of PLAbased coatings most useful in the development of packaging materials. “Influence of different box preparations on creep performance of corrugated fibreboard boxes subject to constant and cycling relative humidity environments”, Page 6 of 15

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Eli M. Gray-Stuart, Kelly Wade, Gabe P. Redding, Kate Parker & John E. Bronlund, Packaging Technology & Science, (2022) online. To understand the effect of load and relative humidity (RH) on box creep in cool storage conditions, standard tests are performed. However, these test conditions are oversimplified compared with actual shipping conditions. Our aim is to develop test conditions that more closely mimic those encountered during refrigerated conditions to investigate their influence on creep performance and box lifetime. We compared three box preparations: (i) empty boxes used as a control, (ii) filled boxes, and (iii) boxes with only two side panels exposed to the atmosphere. A controlled environment test facility was used to subject sets of 24 boxes to 30% of their ultimate failure load under different cyclic and constant relative humidity conditions. Results indicate that filled boxes had substantially reduced performance in terms of secondary creep rate and lifetime. The fill in the box contributed to out-of-plane displacement of the side panels which manifested earlier than in the control, resulting in a higher creep rate. Boxes with only two exposed panels had lower moisture uptake and performed substantially better than the control. These findings demonstrate how creep performance and box lifetime depend on the box conditions including fill and the area of the box that is exposed for moisture transfer. Alternative box preparations which mimic supply chain conditions are worthy of investigation in creep analysis as they will help predict more accurately box performance in the cold supply chain. PAPERMAKING “Optimization Methods For Control Systems of The Headbox And The Cross Direction Control on Papermaking Machines”, Zhe Mo, Journal of Physics: Conference Series 2183 (2022) 012019. This paper briefly introduces the Headbox and the Cross Direction, and analyses challenges in their control systems. The main challenges in these two control systems are nonlinearity and parameter coupling. To solve these problems, or at least reduce the influence of these problems on the control systems, a few optimization methods are proposed. In this paper, some practical optimization methods are introduced based on modified PID control, which is the most commonly used control system in process industries, such as the paper-making industry. Those methods optimizing the PID control system can be mainly divided into two classes: decoupling and PID tuning. Besides, some practical methods optimizing the Cross Direction control systems are introduced. Also, the introduced methods can be divided into two classes: CD tuning and cooperating with parameters of the headbox system to optimize. The effectiveness of these methods is demonstrated in simulations. However, since the nonlinearity of the system, there is no accurate and unique solution. In addition, with the development of demand and technology, there will be no such thing as an algorithm suitable for every control system, so that new algorithms will be proposed. “Design of SA and GA Optimized PID Controllers for Controlling Blend Chest Level of Paper Mill”, Abhijit Singh Bhakuni, Sandeep Kumar Sunori, Shweta Arora, Amit Mittal, Prakash Garia, Sudhanshu Maurya & Pradeep Juneja, 4th IEEE International Conference on Smart Systems and Inventive Technology (ICSSIT), 2022. The present research paper is based upon the blend chest process pertaining to the paper making mill. There is always a requirement of controlling the outputs of multiple units involved in paper making like blend chest, headbox, wire, press section, dryer, calender, and reel unit. The final output is good quality paper rolls. To achieve this control, automatic feedback controllers are employed in paper mills. In this work, 2 different optimization algorithm viz. Simulated Annealing (SA) and Genetic Algorithm (GA) have been utilized to develop the control system using the MATLAB for monitoring of the blend chest process. At the end, the performance comparison of the developed control systems is performed. Page 7 of 15

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Volume 8, Number 1, 2022

“Adsorption of paper strength additives to hardwood fibres with different surface charges and their effect on paper strength”, Mengxiao Zhao, Leif Robertsén, Lars Wågberg & Torbjörn Pettersson, Cellulose, Vol.29, pp.2617-2632 (2022). Light-weight paper products that contain less fibres, but with a maintained bulk and improved strength properties, are highly desirable due to the low cost of raw materials and improved logistics of packaged goods. In this respect, the adsorption capacity of dry strength additives onto fibres, which is affected by the surface charge of said fibres, is very important for the development of these mechanically robust paper products. The influence of the surface charge on the adsorption of strength additives was investigated for, dissolving grade fibres, kraft fibres and kraft fibres modified with carboxymethyl cellulose (CMC) with different surface charge densities, but the same fibre dimensions. The strength additives investigated were cationic starch (CS), anionic polyacrylamide (APAM) and polyelectrolyte complexes (PECs), containing CS and APAM. A linear relationship was found between the surface charge of the fibres and the saturated adsorbed amount of CS. However, when either APAM or PECs adsorbed as secondary layers onto the CS, no correlation between cellulose charge and the saturation adsorption could be observed. The adsorption of APAM was dramatically affected by the pre-adsorbed amount of CS, whereas PECs were less influenced. Moreover, the additives improved the tensile strength (60%) and strain at break (> 100%) of handsheets formed with the kraft fibres and adsorbed APAM. It was also found that CS/APAM increased the sheet density while CS/PECs lowered it. In conclusion, the gained fundamental understanding of these adsorption of additives is of significant importance to facilitate the industrial development of sustainable low-cost highend packaging products. “Cross-linked cationic polyvinyl alcohol for improving mechanical strength of paper”, Kaibin Li, Xiaorui Li, Dan Wang, Chunsheng Zhou & Yiding Shen, Journal of Applied Polymer Science, (2021) online. Cross-linked cationic polyvinyl alcohol (CPVA) is obtained by solution polymerization using vinyl acetate (VAc) and N(isobutoxymethyl)acrylamide (IBMA) as main raw materials and free radical copolymerization using glycidyl methacrylate (GMA) and dimethylaminoethyl methacrylate (DM) as modified monomers. The structure is characterized by HNMR. The effects of DM monomer on the properties of CPVA are investigated. It turns out that CPVA dispersion is a Bingham fluid with good stability. The particle size of CPVA reaches minimum and the value is 147.2 nm, which is in favor of infiltration into the paper. It is more suitable for the DM dosage ranging from 2% to 2.5% in light of the mechanical properties of CPVA film. The obtained CPVA is amorphous and the degree of crystallinity is decreased. When used as surface sizing agent for paper, the water absorption of the sizing paper reaches minimum and the folding resistance reaches maximum when DM is 2.5%. The maximum dry and wet tensile indexes of the paper are increased by 190.71% and 331.09%, respectively. SEM results shows that the larger pores between the paper fibers are filled and cross-linked after CPVA sizing, which is beneficial to the improvement of paper strength. PULP “Engineered invasive plant cellulose fibers as resources for papermaking”, Tea Kapun, Janja Zule, Ema Fabjan, Brigita Hočevar, Miha Grilc & Blaž Likozar, European Journal of Wood and Wood Products, (2022) online. Seven fast-growing invasive plant species were harvested in Slovenia and tested for their valorisation potential in the pulp and paper industry with the aim of sustainable substitution of commercial cellulose fibres. Cellulose fiber materials were isolated by filtration after solubilizing extractives, lignin and hemicellulose in a kraft pulping process. The chemical structure was Page 8 of 15

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thoroughly studied, as well as the optical, morphological and mechanical properties. All examined species (Ailanthus altissima, Fallopia bohemica, Fallopia japonica, Rhus typhina, Robinia pseudoacacia, Rudbeckia laciniata and Solidago canadensis) contain relatively high amount of C6 polysaccharides (> 35%), have notable hemicellulose content (30–40%), low ash content (< 2%) and can be easily delignified, while manufactured natural fibers exhibit convenient morphology (fiber length 0.47–0.88 mm; width 14.4–20.9 μm), optical (ISO whiteness 19.0–36.0%) and mechanical characteristics (tensile index 18.0–58.0 Nm/g; tear index 0.8–4.1 mN m2/g; and burst index 0.5–2.4 kPa m2/g indices), which makes them applicable to sustainable paper production. The pulp yields varied between 34–44%, where both darker herbaceous and brighter woody fibers were morphologically comparable to typical hardwoods. According to the observed properties Robinia pseudoacacia and Rudbeckia laciniata seem to be superior raw material for commercial papermaking products. The ubiquitous invasive plants pose a huge potential for the circular economy, especially in terms of their cascade valorisation of biorefinery by the isolation and valorization of hemicellulose, sugars, and lignins into added-value aromatic and aliphatic building blocks. However, promising yield of cellulose fibers of decent morphology and mechanical properties are reported in this study. “Influences of Fiber and Pulp Properties on Papermaking Ability of Cellulosic Pulps Produced from Alternative Fibrous Raw Materials”, Edyta Małachowska, Aneta Lipkiewicz, Marzena Niemczyk, Marcin Dubowik, Piotr Boruszewski & Piotr Przybysz, Journal of Natural Fibers, Vol.18(11), pp.1751-1761, (2021). The analyzes of cellulosic fibers and properties of cellulosic pulps are extremely important in the process of paper production. If the set point is known, we can predict fairly accurately the effects of fiber dimensions and pulp properties on the final product, which would consequently help in the precise selection of fibrous raw material types suitable for specific recipes and paper applications. In this study, the correlations between the dimensions of cellulosic fibers of alternative fibrous raw materials, pulp properties, and paper were investigated to predict paper strength based on the parameters characterizing the pulp. “Novel bulking technologies for cellulose fibres”, Tom Lindström & Gunborg GladNordmark, Nordic Pulp & Paper Research Journal, (2022) online. This paper deals with the details of preparation of three principal routes for bulking of cellulose fibres. One route is dry cross-linking/hornification using aluminium ions and other salts followed by drying/curing. The mechanisms of these reactions still remain unknown. A second route is physical grafting of fibres using carboxymethylcellulose and bringing the acidic groups into their aluminium form before forming a sheet of paper/board. Hence, curing is not necessary, and this constitutes a unique wet bulking methodology. The mechanism behind this method is believed to be an increase in the surface friction of fibres, when the electrostatic double layer is shielded together with electrostatic cross-linking with aluminium ions. The higher friction between fibres partly prevents the sheet consolidation during drying. A third route is physical grafting of fibres using carboxymethyl cellulose and ion-exchanging the acidic groups with aluminium salts before drying and curing of the fibres. A most interesting factor is that all the thermal treatment methods do not form fibre nodules due to interfibre crosslinking during the heat treatment, a commonly observed phenomena when dealing with chemical crosslinking of fibres. All routes investigated are water-based and should be fairly simple to implement in commercial operations. An inherent advantage is that the bulking is associated with lower water retention values, which should be advantageous for a higher solids content after pressing and, hence, beneficial for paper machine productivity. Bulking is, however, also associated with a loss in bond strength, which in most cases must be alleviated using various additives such as Page 9 of 15

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starches and microfibrillated cellulose and it has also been demonstrated in the project how the strength properties (such as z-strength) could be restored at a higher bulk. TESTING “Novel method for the evaluation of mechanical property of pigment coating layer and its application: Influence of spreading of latex binder on final properties of coating layer”, Jee-Hong Lee & Hak Lae Lee, Progress in Organic Coatings, Vol.163, February 2022, 106652. The mechanical properties of paper coating layers are important in various processes and applications. Proper evaluation of the coating layers is essential for improving coating layer design. In this study, a novel method for the evaluation of the mechanical properties of coating layers was developed using a surface and interfacial characterizing analysis system (SAICAS) instrument, which has an important advantage of not requiring any special sample preparation process. Failure analysis results showed that the SAICAS method provided uniform and reproducible sectioning of the coating layer regardless of the layer's mechanical strength, indicating this is suitable for measuring the mechanical properties of coating layers. The influence of the spreading of latex binder on the final properties of the coating layer was examined and its correlations with structural properties were quantitatively analyzed. This was applied to analyze the mechanical, topographical, and optical properties of coating layers. The results showed that the peel strength and gloss were highly correlated with the spreading of latex. The chemical composition of S/B latex also influenced the peel strength of the coating layer. The transitions observed in the length distribution of pigment–binder interfaces greatly influenced the properties of the coating layer, including peel strength, gloss, and lightscattering efficiency. “Novel Dynamic Test Methods for Paperboard Composite Structures”, Abolhasan Nazarinezhad Giashi, T. Gereke, T. Mbarek & C. Cherif. Experimental Techniques, (2021) online. Paperboard-based composites, typically in the form of carton plies, polyethylene, and aluminum foil, are widely used for food packaging applications. The main goal of packaging converting procedures is to create robust and well-shaped commercial packages. This high speed process is very dynamic, resulting in enormous deformation rates within a few milliseconds. In contrast to previous quasi-static investigations, the envisaged dynamic material characterization for soft and thin paperboard plies will help understand and predict the material response during this high speed packaging process. Even though several experimental standards are already available for paperboard tensile tests, these standards are limited to conventional quasistatic test procedures. Specific cylindrical clamps made of aluminum were designed to prevent samples with a thickness of 100 m from slipping. By means of accurate measuring techniques, a maximum strain rate of 80 s-1 was achieved, which effectively corresponded to actual strain rates that occur in paperboard converting procedures. It was shown that paperboard plies exhibited anisotropic properties and rate-dependent characteristics. Compared to quasi-static properties, the dynamic experiments revealed stiffer hardening properties at higher strain rates. A rate-dependent material model based on CowperSymonds and Johnson-Cook analytical laws was generated to formulate a paperboard dynamic constitutive model. Experimental investigations towards analytical material formulations were successfully conducted to predict and determine the rate dependent material characteristics of paperboards plies at high strain rates. “Experimental quantification of differences in damage due to in-plane tensile test and bending of paperboard”, Gustav Marin, Mikael Nygårds & Sören Östlund, Packaging Technology & Science, (2021) online. Creasing is an essential process to Page 10 of 15

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g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

convert paperboards into packages since it enables folding along well-defined lines. The creasing process relies on purpose-made damage that is initiated in the paperboard structure: delamination. However, creasing might also cause in-plane cracks, which must be avoided. In this laboratory study, three paperboards were creased at six different depths, respectively. Two mechanical tests were performed to characterize the creases at standard climate (23°C and 50% RH): 2-point folding, to examine the bending force and short-span in-plane tensile test to evaluate the strength. The results were normalized with the values for the uncreased boards, which gave the relative strength ratios: relative creasing strength (RCS) and relative tensile strength (RTS). When the relative strengths were evaluated against the normative shear strains, a creasing window was formed. This window has an upper limit given by the RTS values, corresponding to the in-plane cracks, and a lower limit given by the RCS values, corresponding to the delamination damage initiated in the paperboard during creasing. It was observed that both the RCS and RTS values exhibit a linear relation against normative shear strain. From this, it was concluded that performing tests at two creasing depths might be sufficient to estimate the lower, and upper, limits for the creasing window in future studies. Finally, the effect of moisture was investigated by creasing, folding and tensile testing at 23°C and 90% RH, which showed that moisture had no clear effect on the RCS or the RTS values. TISSUE “Application of additives to manufacture quality towel grade tissue paper with accelerated productivity”, Sanjeev Kumar Jain, Dharam Dutt & R.K. Jain, Materials Today Proceedings, (2021) online. Nowadays in paper business sector there is only tissue paper business where growth rate is in double digits since five years consecutively which motivates and encourage entrepreneurs to take up the business with more vigor. Tissue paper is generally categorized in four grades - Napkin grade paper, Toilet grade paper, Facial grade paper and Towel grade paper. Due to higher consumption of towel grade tissue paper at several outlets like offices, educational institutions, aesthetic purposes, common toiletries and hospitalities. This towel grade is being used for wiping wet hands, to meet out these requirements we need to develop high strength in towel grade tissue paper. This study is being conducted to high strength in towel grade tissue paper with application of DSR and WSR. Chemical additives play essential role in production performance of towel grades tissue paper. A significant amount of their tensile strength are retained by wet and dry strength resins. Mixed bleached pulp was collected from pulp mill of a well-known industry. It was refined to different degrees of freeness (°SR) i.e. 25, 30 and 35. Handsheets of pulp refined to different extent, were prepared and physical properties investigated. Based on the specific energy consumption of refiner and the pulp strength properties obtained, pulp freeness with 35°SR were selected for further study. DSR was added in three different doses i.e. 2.0, 3.0 & 4.0 kg/ton and WSR in dosages of 15, 25 & 35 kg/t of pulp. Breaking length and wet strength were enhanced by 32 % and 42 % respectively. On account of this, significant reduction in paper breaks observed on paper machine, which further improved machine runability, reducing downtime. Productivity of machine was enhanced along with supreme quality of towel (interfold) grade tissue paper. “Computational Simulation Tools to Support the Tissue Paper Furnish Management: Case Studies for the Optimization of Micro/Nano Cellulose Fibers and PolymerBased Additives”, Flávia P. Morais, Ana M. M. S. Carta, Maria E. Amaral & Joana M. R. Curto, Polymers, Vol.13(22), (2021). Tissue paper production frequently combines two main types of raw materials: cellulose fibers from renewable sources and polymer-based additives. The development of premium products with improved properties and Page 11 of 15

Technical Abstracts

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

functionalities depends on the optimization of both. This work focused on the combination of innovative experimental and computational strategies to optimize furnish. The main goal was to improve the functional properties of the most suitable raw materials for tissue materials and develop new differentiating products with innovative features. The experimental plan included as inputs different fiber mixtures, micro/nano fibrillated cellulose, and biopolymer additives, and enzymatic and mechanical process operations. We present an innovative tissue paper simulator, the SimTissue, that we have developed, to establish the correlations between the tissue paper process inputs and the end-use paper properties. Case studies with industrial interest are presented in which the tissue simulator was used to design tissue paper materials with different fiber mixtures, fiber modification treatments, micro/nano fibrillated cellulose, and biopolymer formulations, and to estimate tissue softness, strength, and absorption properties. The SimTissue was able to predict and optimize a broader range of formulations containing micro/nanocellulose fibers, biopolymer additives, and treated-fiber mixtures, saving laboratory and industrial resources “Dust Exposures in Swedish Soft Tissue Paper Mills”, Richard L Neitzel, Marianne Andersson, Susanna Lohman, Gerd Sällsten, Kjell Torén & Eva Andersson, Annals of Work Exposures and Health, Vol.66(1), pp.14–26, (2022). We compiled 1578 measurements from 1971 to 2009, of which 1026 (65%) were personal samples. Statistically significant differences were found between measurements made by research, mill, and Swedish Work Environment Authority staff, as well as between personal and area measurements. The measurement data suggest that, beginning in the 1980s, exposures declined at three of the four mills, but that overexposures were still common at the end of the period. Papermaking and converting operations had the highest observed dust exposures. One mill had significantly lower exposures than the others. Type of measurement (personal versus area) and source of measurement (research staff, company, or regulatory agency) were not significant predictors of measured total dust exposure after controlling for mill, operation, and time. Our analysis of measured paper dust exposures may be useful for historical and contemporary exposure assessment in our own and other epidemiological studies. We have identified specific characteristics (i.e. papermaking operations and mill) and time trends that are important data features to consider, and documented continuing overexposure situations. Our results highlight the ongoing need for application of exposure controls to reduce paper dust exposures in the soft tissue paper industry. WASTE TREATMENT “Combined sedimentation, electrocoagulation and ozone processes for the wastewater treatment in an Ecuadorian MDF industry”, C. Navas-Cárdenas, S. Rajendran, T. Ramírez & F. Muñoz, International Journal of Environmental Science and Technology, (2022) online. The combination of sedimentation, electrocoagulation (EC) and ozonation processes was investigated to treat wastewater from a mediumdensity fiberboard panel industry. The set-up of the EC process was composed of aluminum anodes and iron cathodes. For the sedimentation, the residence time was studied in a range from 5 to 120 min, achieving 80% suspended solids removal at 60 min. Three current densities have been investigated for EC: 57.1, 128.6 and 214.3 A/m 2. The addition of 20 mL/min of polyamide (100 mg/L) was also tested using 200 mL/min of wastewater at an initial pH of 7.5 in order to analyze its effect on the pollutant removal, and therefore, on EC performance. The best operating EC conditions were 214.3 A/m2 of current density by the addition of polyamide aqueous solution. After EC, chemical oxygen demand (COD), color and turbidity removals of 66.3%, 99.7% and 99.9%, respectively, Page 12 of 15

Technical Abstracts

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

were obtained. For the ozonation process, an ozone flow of 2.5 g/h was fed to the wastewater, at an initial pH of 7.4. The effect of various ozone doses on COD, color and turbidity removal has also been studied. The highest achieved removal rates were 38.0%, 10.5% and 0.3% for COD, color and turbidity, respectively, at 20 min ozonation time. For the overall treatment, the removal percentages of these parameters were 90.9%, 99.7% and 99.9%, respectively. Furthermore, the combined treatment increased the wastewater biodegradability by a factor of 4.5. Thus, the combined processes of sedimentation, EC and ozonation can be a suitable alternative to reduce contaminant load in effluents from wood industries, and therefore, to comply with the Ecuadorian regulations. “Water quality prediction model using Gaussian process regression based on deep learning for carbon neutrality in papermaking wastewater treatment system”, Xin Wan, Xiaoyong Li, Xinzhi Wang, Xiaohui Yi, Yinzhong Zhao, Xinzhong He, Renren Wu & Mingzhi Huang, Environmental Research, Vol.211, Aug. 2022, 112942. Wastewater recycling is the measure with enormous potentiality to achieve carbon neutrality in wastewater treatment plants. High-precision online monitoring can improve the stability of wastewater treatment system and help wastewater recycling. A new water quality prediction CSWLSTM-GPR model, which fused the spatial feature of convolutional neural network (CNN), the temporal feature of sharing-weight long short-term memory (SWLSTM) and the probabilistic reliability of Gaussian process regression (GPR), was applied for monitoring papermaking wastewater treatment system with high-precision point prediction and interval prediction. Compared with SWLSTM-GPR and CLSTM-GPR, RMSE of CSWLSTM-GPR reduced by more than 48.9% on effluent chemical oxygen demand (CODeff), MAE reduced by more than 49.3%, R2 increased by more than 25.14%, R increased by more than 7.07%. And for the effluent suspended solids (SSeff), CSWLSTM-GPR had better predictive results than SWLSTM-GPR and CSWLSTM-GPR. Compared with SWLSTM-GPR, RMSE, MAE, R, R2 of CSWLSTM-GPR on effluent suspended solids (SSeff) were improved by 4.8%, 6.1%, 29.01% and 31.15%, respectively. Simulation results showed convincing comprehensive forecasting ability were obtained and the true values frequently stayed within the water quality range obtained by CSWLSTM-GPR model, which provided important insights for online monitoring, wastewater recycling and carbon neutrality of papermaking industry. “Evaluation of Discharged Untreated Wastewater from Pulping and Bleaching Operations in a Bamboo Based Tissue Paper Making Plant in Nigeria”, Akpan I. E., Achadu M. Abah & Chukwuma F. O, Research and Analysis Journal, Vol.5(1), (2022). This study on Evaluation of Discharged Untreated Wastewater from Pulping and Bleaching operations in a Bamboo Based tissue Paper Making Plant in Nigeria was conducted mainly to evaluate the pollutant loads present in wastewater produced during the Pulping and Bleaching operations of the tissue paper making progression. The wastewater samples were obtained and examined to find out the pollutants they contain by checking the availability of some physicochemical parameters using standard methods by American Public Health Association (APHA). The analyzed parameters obtained for the pulping and bleaching processes respectively are pH (7.42 and 4.49), EC (316μS/cm and 47μS/cm), TDS (158mg/l and 24mg/l), Turbidity (19.3NTU and 28.7NTU), Temperature (28.47°C and 28.48°C), DO (3.66mg/l and 1.93mg/l), BOD5 (74.02mg/l and 62.00mg/l), COD (140.30mg/l and 120.40mg/l), TOC (10.3% and 7.1%), THB (1.60x103cfu/ml and 7.40x104cfu/ml), THF (0cfu/ml and 2.30x103cfu/ml) and heavy metals like Hg (<0.001mg/l and <0.001mg/l), Pb (0.281mg/l and 0.273mg/l), Ni (0.115mg/l and 0.117mg/l), Co (0.193mg/l and 0.208mg/l) and As (<0.001mg/l and <0.001mg/l). These results were also compared amid the permissible regulatory standards set by the FMEnv and NESREA. Page 13 of 15

Technical Abstracts

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

From the comparative analysis, the bleaching wastewater sample was more polluted than that from pulping. EC, TDS, BOD5, COD, TOC and Pb were higher in the pulping wastewater sample which could be attributed to the organic nature of the starting material; bamboo and residues of the pulping agents; caustic soda and ammonia while Acidity, Turbidity, Temperature, DO, Ni, Co, THB and TF were higher in the bleaching wastewater sample and could be caused by the bleaching agents and the availability of microorganisms. The result showed that some parameters except BOD5, turbidity, COD, DO and pH from pulping fell within regulatory limit. This could be linked to the virgin fibre from bamboo applied which contains less pollutant compared to other industries using waste papers from different sources. WOOD PANEL “Strength Properties of Full-Size Oriented Strand Board Panels Following Submergence in Potable and Salt Water”, Tyler Strayhorn, Phil Mitchel & David Tilotta, Forest Products Journal, 72(1):, pp.58-66, (2022). One of the largest contributors to the economic loss from floods is the complete or partial destruction of residential buildings, and finding ways to eliminate or minimize this loss is important. Oriented strand board (OSB) is a wood product commonly used in home construction, so a better understanding of how flood water affects its mechanical properties is warranted. In this study, the moduli of elasticity and rupture (MOE and MOR, respectively) of representative samples removed from full-size (4 by 8-ft [1.2 by 2.4 m]) OSB panels were examined following the submergence of the panels in potable and salt water (surrogates for flood water) for increasing periods of time (i.e., 8, 24, 48, 72, 168, and 336 h). The results of our study show that after 8 hours of panel submersion in potable water, MOR and MOE is reduced by 15 percent and 16 percent, respectively; no significant change was observed in MOR and MOE for panels soaked in salt water. After 168 hours, the MOR loss was 43 percent for panels soaked in potable water and 38 percent for panels soaked in salt water. For MOE, there was a 35 percent loss regardless of water type. Submersion of panels in either water type for an additional 168 hours resulted in no significant change in MOR or MOE. The MOR and MOE of samples removed from the edges of the submerged panels, for both water types, were lower than those of the interior samples. Finally, the decreases in average MOR and MOE following submergence in either water type were approximately independent of brand. “Utilization of activated carbon as an additive for urea-formaldehyde resin in medium density fiberboard (MDF) manufacturing”, Rohullah Zamani, Saeed Kazemi Najafi & Habibollah Younesi, Journal of Adhesion Science and Technology, (2021) online. In this study, the MDF sanding dust was examined as a precursor for synthesizing activated carbon (AC). For this purpose, MDF sanding dust was impregnated with KOH at two different weight ratios 1:0.50 and 1:1 (sanding dust/KOH). The process was done in one step at a temperature of 750 °C and a heating rate of 8 °C/min. The synthesized ACs at different content were added into urea-formaldehyde (UF) resin for medium density fiberboard (MDF) production. The laboratory MDF boards were produced using a hot press at a temperature of 190 °C and pressure of 40 MPa. The ACs content in UF resin was set at 0.25%, 0.50% and 1% based on the dry weight of the resin. The ACs were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET equation was used to determine the specific surface area of the AC samples. Water absorption, thickness swelling, internal bonding, flexural modulus and strength, and the formaldehyde emission from MDF boards were determined. The curing behavior of UF resins were evaluated using Differential Scanning Calorimetry (DSC). The results revealed that surface area and micropore volume of ACs increase with Page 14 of 15

Technical Abstracts

g PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL ®

Volume 8, Number 1, 2022

increasing KOH ratio; and the ACs exhibited three-dimensional porous network structures. The DSC results also showed that the ACs significantly increase the reaction enthalpy of UF resins. The addition of AC as an additive to UF resin significantly reduces formaldehyde release from MDF boards and improves their physical and mechanical properties. “Effect of Calcite Addition on Technical Properties and Reduction of Formaldehyde Emissions of Medium Density Fiberboard”, Osman Camlibel, BioResources, Vol.16(2), pp.3718-3733 (2021). Physical, mechanical, and formaldehyde emission properties were studied for medium density fiberboard (MDF) produced with oak (75%) and pine (25%) fibers that had been mechanically refined in the presence of calcite particles. The calcite slurry was prepared at two levels of solids, 1.5% and 3% (10 and 20 kg·m<sup>-3</sup>). Chips were cooked for 4 min at 185 °C, under 8 bar vapor pressure in an Andritz defibrillator. 1.8% liquid paraffin, 0.72% ammonium sulphate solution, and 11% urea-formaldehyde were added by percentage based on oven-dried wood fibers in the blowline at the exit of the defibrator. The fibers were dried to 11% moisture content. MDF boards (2100 mm × 2800 mm × 18 mm) were created using a continuous hotpress process. The addition of calcite in the course of MDF production resulted in improved physical properties, such as thickness swelling (ThS 24 hours) and water absorption (WA 24 hours). MDF boards prepared with calcite exhibited higher internal bond (IB), modulus of rupture (MOR), and modulus of elasticity (MOE). Resistance to axial withdrawal of screw also was increased by addition of 3% calcite. In addition, the lowest levels of formaldehyde emission were observed for MDF prepared with calcite at the 3% level.

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Technical Abstracts