Polímeros: Ciência e Tecnologia (Polimeros) 1st. issue, vol. 28, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.2801

After 12 years Profa. Regina Celia Nunes departs as Associated Editor of Polímeros Sebastião V. Canevarolo1 1

Editor-in-Chief, Polímeros, Departamento de Engenharia de Materiais – DEMa, Universidade Federal de São Carlos – UFSCar, São Carlos, SP, Brasil

As already mentioned in past editorials, from now onwards all articles of Polímeros will be published in English.

With this major step forward Polímeros can be available to the broadest scientific community, from any part of the world, just enough to have an internet connection nearby. Now we can say that its original objectives, to spread the latest achievements of the polymer researchers, is been fully attained.

In the last few years Polímeros is steadily getting greater recognition by the researchers working in the polymer area.

This has led to a great increase in the influx of submitted articles, and more important of all, having better fundamental scientific importance. The consequence was the increase of the number of accepted article to be published. In its last meeting the Council Board of Polímeros has decided to increase the number of articles to be published to 60 per year, keeping the number of articles per issue constant of 12. Then the number of issues has been raised to five per year, with the following periodicity: 1º Issue (Jan, Feb, Mar), 2º Issue (Apr, May), 3º Issue (Jun, Jul), 4º Issue (Aug, Set) e 5º Issue (Oct, Nov, Dec).

After serving as Associated Editor of Polímeros for 12 years Profa. Regina Celia Reis Nunes of Universidade Federal do Rio de Janeiro-UFRJ has retired. We acknowledge her great job, responsible for the articles dealing with vulcanized natural and synthetic rubbers and elastomers, publishing many articles in Polímeros, the most recent ones[1-4]. She will remain as member of the Editorial Board, helping us with her deep knowledge stored from many decades of working experience. Thank you Profa. Regina, the whole community is indebted to you.

References 1. Silva, V. M., Nunes, R. C. R., & Sousa, A. M. F. (2017). Epoxidized natural rubber and hydrotalcite compounds: rheological and thermal characterization. Polímeros: Ciência e Tecnologia, 27(3), 208-212. http://dx.doi.org/10.1590/0104-1428.03416.

2. Honorato, L., Dias, M. L., Azuma, C., & Nunes, R. C. R. (2016). Rheological properties and curing features of natural rubber compositions filled with fluoromica ME 100. Polímeros: Ciência e Tecnologia, 26(3), 249-253. http://dx.doi.org/10.1590/01041428.2352.

3. Bezerra, F. O., Nunes, R. C. R., Gomes, A. S., Oliveira, M. G., & Ito, E. N. (2013). Efeito Payne em nanocompósitos de NBR com montmorilonita organofílica. Polímeros: Ciência e Tecnologia, 23(2), 223-228. http://dx.doi.org/10.1590/S0104-14282013005000022.

4. Mariano, R. M., Nunes, R. C. R., Visconte, L. L. Y., & Altstaedt, V. (2013). Effect of montmorillonite and cellulose ii hybridization on mechanical properties of natural rubber nanocomposites. Polímeros: Ciência e Tecnologia, 23(1), 123-127. http://dx.doi. org/10.1590/S0104-14282013005000012.

Short CV of Profa. Dra. Regina Celia Reis Nunes She holds a Licentiate degree in Chemistry from Universidade Estadual do Rio de Janeiro (1968), a Master’s degree in Organic Chemistry from the Instituto de Química of the Universidade Federal do Rio de Janeiro, UFRJ (1975), a PhD in Polymer Science and Technology from the Instituto de Macromoléculas of the UFRJ (1989) and Post-Doctorate by the Consejo Superior de Investigaciones Científicas, Madrid, Spain (1994). She is Adjunct Professor 4 at UFRJ since 1990 and is currently a Guest Professor at the Instituto de Macromoléculas Professor Eloísa Mano of the UFRJ. She is an expert in Rubbers and Elastomers, working mainly on the following topics: Polymer/cellulose nanocomposites, Elastomeric composites with special properties, and Mineral loading in polymer compositions. She was a member of the Editorial Board of Polímeros as Associated Editor since 2006.

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ISSN 0104-1428 (printed)

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ISSN 1678-5169 (online)

P o l í m e r o s - I ss u e I - V o l u m e X X V I I I - 2 0 1 8 I n d e x e d i n : “ C h e m ic a l A b s t r a c t s ” — “ RA P RA A b s t r a c t s ” — “A l l - R u s s i a n I n s t i t u t e o f S ci e n c e ­T e c h n ic a l I n f o r m a t i o n ” — “ R e d d e R e v i s t a s C i e n t i f ic a s d e A m e r ic a L a t i n a y e l C a r i b e ” — “ L a t i n d e x ” — “ W e b o f S ci e n c e ”

and

Polímeros E d i t o r i a l C o u nci l Antonio Aprigio S. Curvelo (USP/IQSC) - President

Editorial Committee Sebastião V. Canevarolo Jr. – Editor-in-Chief

Members Adhemar C. Ruvolo Filho (UFSCar/DQ) Ailton S. Gomes (UFRJ/IMA) Alain Dufresne (Grenoble INP/Pagora) Antonio Aprigio S. Curvelo (USP/IQSC) Bluma G. Soares (UFRJ/IMA) César Liberato Petzhold (UFRGS/IQ) Cristina T. Andrade (UFRJ/IMA) Edson R. Simielli (Simielli - Soluções em Polímeros) Edvani Curti Muniz (UEM/DQI) Elias Hage Jr. (UFSCar/DEMa) Eloisa B. Mano (UFRJ/IMA) João B. P. Soares (UAlberta/DCME) José Alexandrino de Sousa (UFSCar/DEMa) José António C. Gomes Covas (UMinho/IPC) José Carlos C. S. Pinto (UFRJ/COPPE) Júlio Harada (Harada Hajime Machado Consutoria Ltda) Laura H. de Carvalho (UFCG/DEMa) Luiz Antonio Pessan (UFSCar/DEMa) Luiz Henrique C. Mattoso (EMBRAPA) Marco-Aurelio De Paoli (UNICAMP/IQ) Osvaldo N. Oliveira Jr. (USP/IFSC) Paula Moldenaers (KU Leuven/CIT) Raquel S. Mauler (UFRGS/IQ) Regina Célia R. Nunes (UFRJ/IMA) Richard G. Weiss (GU/DeptChemistry) Rodrigo Lambert Oréfice (UFMG/DEMET) Sadhan C. Jana (UAKRON/DPE) Sebastião V. Canevarolo Jr. (UFSCar/DEMa) Silvio Manrich (UFSCar/DEMa)

A ss o ci at e E d i t o r s Adhemar C. Ruvolo Filho Alain Dufresne Bluma G. Soares César Liberato Petzhold José António C. Gomes Covas José Carlos C. S. Pinto Paula Moldenaers Richard G. Weiss Rodrigo Lambert Oréfice

Sadhan C. Jana

D e s k t o p P u b l is h in g

www.editoracubo.com.br

“Polímeros” is a publication of the Associação Brasileira de Polímeros São Paulo 994 St. São Carlos, SP, Brazil, 13560-340 Phone: +55 16 3374-3949 emails: abpol@abpol.org.br / revista@abpol.org.br http://www.abpol.org.br Date of publication: March 2018

Financial support:

Polímeros / Associação Brasileira de Polímeros. vol. 1, nº 1 (1991) -.- São Carlos: ABPol, 1991Available online at: www.scielo.br

Quarterly v. 28, nº 1 (Jan./Fev./Mar. 2018) ISSN 0104-1428 ISSN 1678-5169 (electronic version)

Website of the “Polímeros”: www.revistapolimeros.org.br

1. Polímeros. l. Associação Brasileira de Polímeros.

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Editorial Section Editorial................................................................................................................................................................................................E1 News....................................................................................................................................................................................................E4 Agenda.................................................................................................................................................................................................E5 Funding Institutions.............................................................................................................................................................................E6

O r i g in a l A r t ic l e Recovery of Terephthalic Acid by employing magnetic nanoparticles as a solid support Elmira Ghamary, Mir Mohammad Alavi Nikje, Seyedeh Leila Rahmani Andabil and Lida Sarchami............................................................... 1

FT-IR methodology (transmission and UATR) to quantify automotive systems Ana Carolina Ferreira, Milton Faria Diniz and Elizabeth da Costa Mattos....................................................................................................... 6

Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite Elilton Rodrigues Edwards, Silvia Sizuka Oishi and Edson Cocchieri Botelho................................................................................................ 15

Nitrile rubber and carboxylated nitrile rubber resistance to soybean biodiesel Felipe Nunes Linhares, Cléverson Fernandes Senra Gabriel, Ana Maria Furtado de Sousa, Marcia Christina Amorim Moreira Leite and Cristina Russi Guimarães Furtado.................................................................................................................................................................... 23

Microstructure and thermal and functional properties of biodegradable films produced using zein Crislene Barbosa de Almeida, Elisângela Corradini, Lucimara Aparecida Forato, Raul Fujihara and José Francisco Lopes Filho............. 30

FSSC 22000 Packaging Implementation: a Plastics Industry Research Vanessa Cantanhede, Karen Signori Pereira and Daniel Weingart Barreto..................................................................................................... 38

Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends Ricardo Mesias and Edwin Murillo................................................................................................................................................................... 44

Stabilization of guava nectar with hydrocolloids and pectinases Fernanda Döring Krumreich, Ana Paula Antunes Corrêa, Jair Costa Nachtigal, Gerson Lübke Buss, Josiane Kuhn Rutz, Michele Maciel Crizel-Cardozo, Cristina Jansen and Rui Carlos Zambiazi.................................................................................................... 53

Cashew nut shell liquid, a valuable raw material for generating semiconductive polyaniline nanofibers Raiane Valenti Gonçalves, Mara Lise Zanini, José Antonio Malmonge, Leila Bonnaud and Nara Regina de Souza Basso............................ 61

Reinforcement of poly (vinyl alcohol) films with alpha-chitin nanowhiskers Hugo Lisboa....................................................................................................................................................................................................... 69

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams Maciej Combrzyński, Leszek Mościcki, Anita Kwaśniewska, Tomasz Oniszczuk, Agnieszka Wójtowicz, Magdalena Kręcisz, Bartosz Sołowiej, Bożena Gładyszewska and Siemowit Muszyński................................................................................................................... 76

Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA Luciana Maria Guadagnini Araujo and Ana Rita Morales............................................................................................................................... 84

Cover: TEM micrograph of synthesized PAni with 25% CNSL. Arts by Editora Cubo

Polímeros, 28(1), 2018

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I I I I I I I I I I I I I I I I I

N N N N N N N N N N N N N

Material gradients could strengthen polymer components

Waters and Malvern Panalytical Collaborate to Improve Polymer Characterization

Combining flexible and stiff materials has bestowed bamboo with a strength-to-weight ratio that rivals steel.

Gradually transitioning from a soft to hard substance allows the squishy squid to slice up prey with rigid, scissor-like beaks. With the help of a new model co-developed at the University of Nebraska-Lincoln, these two evolution-honed principles could eventually enable engineers to double or triple the strength of polymer-based components. Natural selection has often favored integrating flexible and stiff materials because they can perform better together – resisting greater forces, supporting heavier loads – than they do alone. These benefits emerge especially when the materials can occupy the same space, as they do in interpenetrating polymer networks: two or more sets of molecular-scale networks that weave throughout one another without actually connecting.

But making the most of these networks also means varying the hard-to-soft ratio across space, creating a gradient. Whereas a 70-30 ratio might work best in one location, 50-50 or 30-70 could be ideal in another.

So Nebraska, French and Chinese researchers refined a model that can map an optimal gradient onto a structure while calculating how much that gradient improves the structure’s performance. “Normally, when you mix things, they separate,” said model co-creator Mehrdad Negahban, professor of mechanical and materials engineering at Nebraska. “You can think of it like an island of one material and an ocean of another material. The island and that ocean have a boundary, and that turns out to be a material’s weakest point. So two materials will essentially fail … where they’re connected. But if you interpenetrate them, you don’t have these weak boundaries.”

The team demonstrated its model by analyzing the tensile strength of a plate with a small hole at its center.

First the researchers measured the strength of a plate made only from a rigid epoxy. When their model optimized a gradient of epoxy interpenetrated with acrylate—a weaker, more flexible polymer—they found that the plate’s tensile strength nearly tripled. Likewise, an L-shaped bracket saw its tensile strength double after the model plotted its optimal epoxy-acrylate gradient. “We change the mixture, but the total weight is approximately the same,” Negahban said. “Just by putting the right stuff in the right place, we can get it to suddenly function much, much better – that is, it’s performing substantially better than the stronger component. “This could go both ways.

You could use this either to reduce the weight or increase the load-bearing capability.”

On a fundamental level, the team’s model works by overlaying a structure with a grid of up to several hundred nodes. It then assigns a ratio of given materials to each node in the grid, calculating how the resulting gradient affects the structure’s overall strength. “It’ll do this millions of times until it finds the (permutation) that can carry the highest load,” Negahban said.

As of now, Negahban said, interpenetrating polymer networks are difficult to actually fabricate. The emergence of 3-D printing has hinted at a potential approach for building components from the networks, though work remains before engineers can easily interlace polymers on the molecular scale. But Negahban said it’s likely just a matter of time before a technique emerges to take fuller advantage of the model he and his colleagues have put forth.

“People are coming up with different ideas of how to (incorporate) them,” he said. “I think it’ll happen.”

Source: Phys.org - http://phys.org/news

Malvern Panalytical announced that it entered into a co-marketing agreement with Waters Corporation (NYSE:WAT) to advance the analysis of polymers.

By pairing the Waters ACQUITY Advanced Polymer Chromatography (APC™) System with Malvern Panalytical’s OMNISEC REVEAL, R&D scientists can access higher sensitivity, higher resolution data than ever before, giving them better insight into their samples without the need for column calibration. The emergence of new and increasingly complex polymers with a broad range of structural and compositional diversity has been a driving force in the development of advanced analytical and separation technologies for polymer characterization.

Today, analysts seek innovative techniques that allow them to better characterize and understand their highly complex samples. Combining high efficiency columns with the low overall system dispersion of Waters’ APC significantly improves resolution, especially for low molecular weight oligomers. In addition, run times can be up to 5X faster than with traditional Gel Permeation Chromatography (GPC), enabling higher sample throughput and more rapid method development. Use of this high speed, high resolution separation technique has historically seen limited pairing with advanced online detectors, such as light scattering, due to limitations in the dispersion characteristics of these detectors. However, as the advantages of the APC become clearer, both in research and industry, manufacturers have been working to reduce dispersion within their advanced detector options, whilst maintaining the high resolution of the APC separation.

Malvern Panalytical has achieved exactly this with its OMNISEC REVEAL multidetector module. Coupling the APC System to the OMNISEC REVEAL offers the ability to calculate absolute molecular weight, intrinsic viscosity and hydrodynamic radius.

These parameters can be used to predict polymer behaviors in solutions/product matrices and to give a more comprehensive understanding of polymer structure.

This speed of analysis and easy access to more detailed information provides a quicker pathway to the development of more successful and efficient products. “Waters takes great pride in collaborating with innovative companies like Malvern Panalytical to solve complex molecular characterization challenges. This is an example of two leaders in our respective fields working together to optimize the combination of our technologies in order to help scientists achieve their analytical goals,” said Jeff Mazzeo, Vice President of Marketing, Waters Corporation. “Malvern Panalytical is proud to work with Waters to leverage the high sensitivity and low dispersion characteristics of the OMNISEC REVEAL advanced detector module, which are ideally suited to the APC system’s high resolution and high efficiency separation characteristics.

We believe that researchers will be delighted with the analytical abilities of the combined system, which offers extraordinary performance for the analysis of both natural and synthetic polymers and provides visibility of details that would otherwise be missed. The combination of Waters’ APC and Malvern Panalytical’s OMNISEC REVEAL opens new doors in polymer research and development which will translate directly to better product performance,” stated Steven Horder, Vice President, Advanced Materials, Malvern Panalytical.

Source: Technology Networks - https://www.technologynetworks.com

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May 5th International Conference on Plastics, Rubber and Composites (ICPRC 2018) Date: May 4–5, 2018 Location: Phuket - Thailand Website: www.icprc.org The International Plastic Showcase Date: May 7–11, 2018 Location: Orlando - USA Website: www.npe.org 34th International Conference of the Polymer Processing Society (PPS-34) Date: May 21-25, 2018 Location: Taipei - Taiwan Website: www.pps-34.com.

World Congress on Biopolymers and Polymer Chemistry Date: May 28–30, 2018 Location: Osaka - Japan Website: biopolymerscongress.conferenceseries.com

June Polymers and Organic Chemistry (POC 2018) Date: June 4–7, 2018 Location: Montpellier - France Website: iupac.org/event/polymers-organic-chemistry-2018poc-2018 4th Functional Polymeric Materials Conference Date: June 5–8, 2018 Location: Nassau - Bahamas Website: www.fusion-conferences.com/conference76.php PLASTEC East Date: June 12-14, 2018 Location: New York – USA Website: plastec-east.plasticstoday.com Argenplás Date: June 13-16, 2018 Location: Buenos Aires - Argentina Website: www.argenplas.com.ar Polymer Gels and Networks Date: June 17-21, 2018 Location: Prague - Czech Republic Website: www.imc.cas.cz/sympo/82pmm_png2018 Polymer Foam Date: June 19-20, 2018 Location: Pittsburgh - USA Website: www.ami.international/events/event?Code=C883 8th World Congress on Biopolymers Date: June 28-30, 2018 Location: Berlin - Germany Website: biopolymers.conferenceseries.com

July IUPAC World Polymer Congress (Macro 2018) Date: July 1-5, 2018 Location: Cairns – Australia Website: www.macro18.org

August 6th International Conference & Exhibition on Advanced & Nano Materials (ICANM 2018) Date: August 6-8, 2018 Location: Quebec - Canada Website: icanm2018.iaemm.com 3rd International Conference on Material Engineering and Smart Materials (ICMESM 2018) Date: August 11-13, 2018 Location: Okinawa - Japan Website: www.icmesm.org

Interplast Date: August 14-17, 2018 Location: Joinville - Brazil Website: www.interplast.com.br 25th Bio-Environmental Polymer Society (BEPS 2018) Date: August 15-17, 2018 Location: New York - USA Website: www.beps.org/meetings 5th International Conference and Exhibition on Polymer Chemistry Date: August 27-28, 2018 Location: Toronto – Canada Website: polymer.conferenceseries.com

September 4th International Conference on Bio-based Polymers and Composites (BiPoCo 2018) Date: September 2-6, 2018 Location: Balatonfüred - Hungary Website: bipoco2018.hu 10th Conference of Modification, Degradation and Stabilization of Polymers (MoDeSt2018) Date: September 2-6, 2018 Location: Tokyo - Japan Website: biz.knt.co.jp/tour/2018/modest/index.html Polymers in Flooring Date: September 20-21, 2018 Location: Atlanta - USA Website: www.ami.international/events/event?Code=C911 Thermosetting Resins 2018 Date: September 25-27, 2018 Location: Berlin - Germany Website: thermosetting-resins.de

October 8th International Conference and Exhibition on Biopolymers and Bioplastics Date: October 15-16, 2018 Location: Las Vegas – USA Website: biopolymers-bioplastics.conferenceseries.com 8th International Conference on Polymer Science and Engineering Date: October 15-16, 2018 Location: Las Vegas – USA Website: polymerscience.conferenceseries.com

November Polymers + 3D Date: November 1-2, 2018 Location: Houston – USA Website: www.poly3d.org 9th International Conference on Biopolymers and Polymer Sciences Date: November 1-2, 2018 Location: Bucharest - Romania Website: biopolymers.materialsconferences.com Regional Conference of the Polymer Processing Society (PPS-Americas) Date: November 5-9, 2018 Location: Boston – Massachusetts - USA Website: www.pps2018boston.com.

December 12th SPSJ International Polymer Conference (IPC 2018) Date: December 4-7, 2018 Location: Hiroshima - Japan Website: main.spsj.or.jp/ipc2018

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A A A A A A A A A A A A A A A A A A A A A

ABPol Associates Sponsoring Partners

Institutions UFSCar/ Departamento de Engenharia de Materiais, SP SENAI/ Serviço Nacional de Aprendizagem Industrial Mario Amato, SP UFRN/ Universidade Federal do Rio Grande do Norte, RN

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ABPol Associates Collective Members A. Schulman Plásticos do Brasil Ltda.

Aditive Plásticos Ltda.

Avamplas – Polímeros da Amazônia Ltda.

CBE – Grupo Unigel Colorfix Itamaster Indústria de Masterbatches Ltda.

Cromex S/A Cytec Comércio de Materiais Compostos e Produtos Químicos do Brasil Ltda.

Formax Quimiplan Componentes para Calçados Ltda.

Imp. e Export. de Medidores Polimate Ltda.

Innova S/A Instituto de Aeronáutica e Espaço/AQI Jaguar Ind. e Com. de Plásticos Ltda Master Polymers Ltda.

Milliken do Brasil Comércio Ltda.

MMS-SP Indústria e Comércio de Plásticos Ltda.

Nexo International Ltda.

Nitriflex S/A Ind. e Com. Politiplastic Politi-ME. Premix Brasil Resinas Ltda.

QP - Químicos e Plásticos Ltda.

Radici Plastics Ltda.

Replas Comércio de Termoplásticos Ltda.

Uniflon - Fluoromasters Polimeros Ind .Com. Imp. Export.Ltda

Polímeros, 28(1), 2018

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ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.2201

Recovery of Terephthalic Acid by employing magnetic nanoparticles as a solid support Elmira Ghamary1, Mir Mohammad Alavi Nikje1*, Seyedeh Leila Rahmani Andabil1 and Lida Sarchami1 1

Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran *drmm.alavi@gmail.com

Abstract The aim of this research work is focused on the improvement of Terephthalic acid recovery from PET wastes by using organically modified nano-Fe3O4@Cyanuric Chloride as the solid support. The performance of organically modified nano magnetic was examined in detail and the obtained results were compared with the unsupported reaction data.

Required reaction time for complete glycolysis of the wastes, consumption of the solvent as well as catalyst decreases up 99%, 37.5% and 40% respectively. Result showed that nano-Fe3O4@Cyanuric Chloride delivered good performance as solid support in depolymerizing of PET to the terephthalic acid.

Keywords: poly (ethylene terephthalate), recycling, solid support, terephthalic acid.

1. Introduction The use of polymer in various application are expanded daily and PET is one of the most consumed polymers as its excellent thermal and mechanical properties. This polymer used in the manufacture of high strength fibers, soft drink bottles and photographic films and at the end of the last century its consumption increased to more than 3,000,000 tons per year[1]. In 2009 the global consumption of PET packaging was almost 15.5 Mt while the estimate is to growth to almost 19 Mt by 2017- a 5.2% increase per annum. By increasing in PET production and since this polymer is not biodegradable, big waste stream create a serious environmental problem each year. Chemical recycling of PET has been attracting attention for both environmental and economic reasons[2].

In this case, Nikje and Nazari[3] and his coworker reported glycolyzing of PET by using methanol, ethanol, 1-butanol, 1-pentanol, and 1-hexanol in the presence of different simple basic catalysts, namely, potassium hydroxide, sodium hydroxide and etc, under microwave irradiation.

Pingale and Shukla[4] research group had been used zinc acetate, sodium carbonate, sodium bicarbonate and barium hydroxide as catalyst for glycolysis PET by using microwave as energy source. In our previously reported data, we glycolized PET by using DEG as the solvent and NaOH as the catalysts under microwave irradiation[5]. Parab et al.[6] used ethanolamine for aminolytic depolymerization of PET bottles wastes with heterogeneous, recyclable acid catalysts such as beta zeolite and montmorillonite KSF under microwave irradiation. Siddiqui [2] reported the using of microwave irradiation as a convenient energy source for recycling of poly (ethylene terephthalate) waste through methanolic pyrolysis. Chen et al.[7] glycolized PET by using excess ethylene glycol (EG) in the presence of zinc acetate as catalysts under microwave irradiation. The glycolysis of PET has been reported by using monoetylene glycol (MEG),

Polímeros, 28(1), 1-5, 2018

diethylen glycol (DEG), monopropylene glycol (MPG) and dipropylene glycol (DPG) in present zinc acetate as catalyst under microwave irradiation[8]. Chaudhary et al.[9] glycolized PET and produced BHET for preparation of polyester polyols under microwave irradiation. Chemical depolymerization of PET complex was done by Liu et al.[10].

Waste depolymerization of PET was done by using bransted acidic ionic liquid under microwave irradiation[11] and in another report PET was glycolized by using several ionic liquids and basic ionic liquids as catalysts[12]. In addition the efficiency of Metal-Containing Ionic Liquids as a highly Effective Catalysts for Degradation of Poly (Ethylene Terephthalate) has been surveyed[13]. All the mentioned catalysts such as alkalies, metal acetate, zeolites, ionic liquids and etc, in the PET glycolysis reactions required long reaction times and contributed low BHET and TPA yields.

In order to resolve these drawbacks and improve reaction conditions Imran et al.[14,15] used thermally stable and highly selective silica nanoparticle-supported metal (Mn, Zn, Ce) oxides as the catalysts for PET depolymerization. After that, Park et al.[16] outstretch graphene oxide and manganese oxide as the catalysts for PET glycolysis. Bartolome et al.[17] used nano-γ-Fe2O3 as an easily recoverable catalyst for the recycling of PET. The number of active sites in nanoscale catalysts increase and also changing inherent properties of the catalysts in nanoscale usually leads to better catalytic performance.

In continuation of our previous work on PET chemical recycling[3,5] we decided to examine the performance of nano-Fe3O4@Cyanuric Chloride as the reagent-solid support in order to recovery TPA from the bottles wastes. By using of this reagent-solid support required time to access to high recovery yield significantly decreases so that is comparable with microwave method.

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O O O O O O O O O O O O O O O O

Ghamary, E., Nikje, M. M. A., Andabil, S. L. R., & Sarchami, L.

2. Experimental 2.1 Preparation of nano-Fe3O4@Cyanuric Chloride The magnetic nanoparticles (Fe3O4, 0.5 g) were dispersed in the Acetonitrile (100 mL) with sonication (20 min).

Then Cyanuric Chloride (0.4 g) was added to the mixture and mechanically stirred at room temperature (7 h). Finally, the core-shell nanoparticles were separated from the reaction medium, and washed with Acetonitrile for two times and then dried at 45 °C in oven overnight and characterized[18].

2.2 PET glycolysis using nano- Fe3O4@Cyanuric Chloride and NaOH For depolymerization, in a three-necked flask, 100 mL round-bottom glass equipped with a condenser, thermometer and magnetic stirrer PET flakes (1 g) was treated with diethylene glycol using different PET: DEG molar ratios (1:4 to 1:8) at 160 °C. The used NaOH and Fe3O4@Cyanuric Chloride were (0.1-0.5 g) and (0.01-0.3 g), respectively. At the end of the reaction, distilled water (70 mL) was added to the reaction mixture with vigorous agitation. Then the TPA in the mixture was precipitated by bringing the pH to 2-3 by addition of HCl and dried at 80 °C in the oven (1 h), characterized and data compared with an authentic sample.

3. Results and discussion 3.1 Nano- Fe3O4@Cyanuric Chloride solid support characterization The FE-SEM image of synthesized magnetite nanoparticles is shown in the Figure 1. From the figure, Fe3O4 nanoparticles and nano-Fe3O4@Cyanuric Chloride have spherical shape with average size of 30-40 and 40-60 nm, respectively.

Figure 2 shows the thermal gravimetry analysis curves (TGA) of Fe3O4 and nano-Fe3O4@Cyanuric Chloride, respectively. In samples there is an insignificant weight loss stage (below 130 °C) that can be imputed to the evaporation of water and ethanol. In addition in modified sample, weight loss started at 200 to 700 °C and correspondent to the thermal decomposition of (Cyanuric Chloride) coating on magnetite nanoparticles. Actually weight loss, the coated Cyanuric Chloride on the surface Fe3O4 NPs is calculated as 12%.

Modification of magnetite nanoparticle with Cyanuric Chloride was confirmed by FT-IR spectroscopy (Figure 3).

The vibrations at 400 cm−1 and 580 cm−1 are attributed to the Fe-O functional groups of magnetite nanoparticle.

The vibrations at 810 cm-1, 1066 cm-1 and 1634 cm-1 refer to C-Cl, C-N and C=N respectively. The vibrations at 3400-3600 cm-1 are attributed to adsorbed O-H by Fe3O4.

Figure 1. FE-SEM image of synthesized Fe3O4 and nano-Fe3O4@ Cyanuric Chloride.

3.2 Depolymerization reaction Figure 4 shows the reaction scheme of TPA recovery.

In this scheme, waste PET flakes received from used bottles were glycolysis in the present nano-Fe3O4@Cyanuric Chloride as the solid support and NaOH as the reagent, by the formation of highly reactive PET- Iron Oxide complex.

Further neutralization of unreacted sodium hydroxides and disodium-TPA salts by hydrochloric acid, TPA crystals was obtained.

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Figure 2. TGA curves for a: Fe3O4 and b: Fe3O4@Cyanuric Chloride nanoparticles.

Polímeros, 28(1), 1-5, 2018

Recovery of Terephthalic Acid by employing magnetic nanoparticles as a solid support

Figure 5. The effect of PET: DEG molar ratios on the glycolysis of PET in the present of Fe3O4@Cyanoric Chloride (0. 02 g) and NaOH (0.30 g).

Table 1. The effect of time on the glycolysis of PET in the present of Fe3O4@Cyanoric Chloride.

Figure 3. FT-IR spectra of a: Fe3O4 and b:nano-Fe3O4@Cyanuric Chloride.

Entry

Fe3O4@Cyanoric Chloride

1 2 3 4 5 6 7 8 9 10 11

(g) 0.00 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02

Time (min)

Unreacted PET

TPA yield

(g) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.32

% 90 95 94 90 90 92 91 90 89 87 54

101 101 50 30 20 15 10 5 2 1 0.5

Table 2. The effect of solid supported catalyst concentration on the glycolysis of PET (1 g) in the present of NaOH (0.5 g) and DEG (7 mL).

Entry

Figure 4. Proposed mechanism for PET glycolysis reaction in the presence of NaOH as the catalyst and nano-Fe3O4@Cyanuric Chloride as the solid support.

1 2 3 4 5 6 7 8

Fe3O4@Cyanoric Chloride

TPA yield

(g) 0.01 0.02 0.03 0.05 0.08 0.10 0.20 0.30

% 77 87 88 87 88 84 82 79

3.3 The role of reagent-solid support on TPA recovery The results of performance of nano-Fe3O4@Cyanuric Chloride as solid support in recovering of TPA collected in Figure 5 and Tables 1-3, respectively and data were compared with our previously reported data without using this solid support[5]. In the present of nano-Fe3O4@Cyanuric Chloride (0.02 g) the required recovery time to access high recovery yield decreases up 99% which is comparable with microwave conducted reaction (Table 1). This can be related to the nano-Fe3O4@Cyanuric Chloride capability to increase surface area rendering more active sites and thermal stability.

Polímeros, 28(1), 1-5, 2018

The results of changing concentration of nano-Fe3O4@ Cyanuric Chloride are collected in Table 2. In entry 2 maximum amount of terephthalic acid yield (87%) was obtained, that is related to presence of nano-Fe3O4@Cyanuric Chloride (0.02 g) in the reaction mixture.

In order to studying of catalyst role, six sets of reactions were handled in the same reaction times and data collected in the Table 3. As shown on entry 4 of Table 3, by decreasing NaOH concentration to 40% sightly value of reaction (entry 1), the TPA recovery yield will remain constant.

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Ghamary, E., Nikje, M. M. A., Andabil, S. L. R., & Sarchami, L. Table 3. The effect of catalyst concentration on the glycolysis of PET (1 g).

Entry

Fe3O4@ Cyanoric Chloride (g)

NaOH (g)

Unreacted PET (g)

TPA yield %

1

0.00

0.50

0.00

90

2

0.02

0.50

0.00

95

3

0.02

0.40

0.00

89

4

0.02

0.30

0.00

87

5

0.02

0.20

0.21

53

6

0.02

0.10

0.52

34

Figure 8. 13CNMR spectra of obtained TPA from Glycolysis.

In order to finding the optimum PET: DEG molar ratios, we decrease this ratio (Figure 5). As shown in this figure, in present of nano-Fe3O4@Cyanuric Chloride (0.02 g) and by altering PET: DEG molar ratios from 1:8 to 1:5, the slight decrements in TPA recovery yield are observed and suddenly drop in 1:4 molar ratio. And this means we have 37.5% saving energy.

3.4 IR spectroscopy analysis of obtained TPA

Figure 6. FT-IR spectra of obtained TPA from Glycolysis.

Figure 6 shows IR Spectroscopy of obtained TPA from glycolysis reaction. Specifications bond at 2500-3250 cm-1 are related to carboxylic group, 1685 cm-1 are related to carbonyl group and 1574-1425 cm-1 are related to aromatic ring. These results have a good match with the reference data related to virgin TPA showing that the purity of the product in this method is passable.

3.5 1HNMR analysis Figure 7 shows 1HNMR spectrum of obtained TPA. The revealed bands at 8.01 ppm and 13.27 ppm are related to protons of aromatic ring and acidic proton respectively and spectrum is similar to the authentic sample one.

3.6 13CNMR analysis Figure 8 shows 13CNMR spectrum of obtained TPA. The revealed band at 167.10 ppm are related to carbon of carbonyl group and 129.93 ppm and 134.86 ppm are related to carbons of aromatic ring and all signals math with an authentic sample spectrum signal.

4. Conclusion

Figure 7. 1HNMR spectra of obtained TPA from Glycolysis.

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In conclusion, nano-Fe3O4@Cyanuric Chloride can be used as the effective supported catalyst in recovering of terephthalic acid from PET wastes in combination with sodium hydroxide. The obtained results from the glycolysis of PET wastes by using DEG as the solvent, sodium hydroxide as the reagent and nano-Fe3O4@Cyanuric Chloride as the reagent-solid support led to successful recovering of TPA Polímeros, 28(1), 1-5, 2018

Recovery of Terephthalic Acid by employing magnetic nanoparticles as a solid support in high yields. In the presences of nano-Fe3O4@Cyanuric Chloride, the required reaction time for TPA recovery, DEG and NaOH consumptions decrease about 99, 37.5 and 40%, respectively.

5. Acknowledgements The authors thank Imam Khomeini International University (IKIU) for the financial support of Dr. Alavi Nikje.

6. References 1. Nikje, M. M. A., Nazari, F., Imanieh, H., Garmarudi, A. B., & Haghshenas, M. (2007). PET recycling by diethylene glycoldiethanol amine binary mixture and application of product in rigid polyurethane foam formulation. Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, 44(7), 753-758. http://dx.doi.org/10.1080/10601320701353231.

2. Siddiqui, M. N., Redhwi, H. H., & Achilias, D. S. (2012).

Recycling of poly(ethylene terephthalate) waste through methanolic pyrolysis in a microwave reactor. Journal of Analytical and Applied Pyrolysis, 98, 214-220. http://dx.doi. org/10.1016/j.jaap.2012.09.007.

3. Nikje, M. M. A., & Nazari, F. (2006). Microwave-assisted depolymerization of Poly(ethylene terephthalate) [PET] at atmospheric pressure. Advances in Polymer Technology, 25(4), 242-246. http://dx.doi.org/10.1002/adv.20080.

4. Pingale, N. D., & Shukla, S. R. (2008). Microwave assisted ecofriendly recycling of poly (ethylene terephthalate) bottle waste. European Polymer Journal, 44(12), 4151-4156. http:// dx.doi.org/10.1016/j.eurpolymj.2008.09.019.

5. Nikje, M. M. A., & Nazari, F. (2009). Simple and convenient method of chemical recycling of poly (ethylene terephthalate) by using microwave radiation. Polimery, 54(9), 635-639.

Retrieved in 2015, July 07, from http://www.ichp.pl/attach. php?id=244 6. Parab, Y. S., Shah, R. V., & Shukla, S. R. (2012). Microwave irradiated synthesis and characterization of 1, 4-phenylene bis-oxazoline form bis-(2-hydroxyethyl) terephthalamide obtained by depolymerization of poly (ethylene terephthalate) (PET) bottle wastes. Current Chemistry Letters, 1(2), 81-90. http://dx.doi.org/10.5267/j.ccl.2012.3.003.

7. Chen, F., Wang, G., Shi, Ch., Zhang, Y., Zhang, L., Li, W., & Yang, F. (2013). Kinetics of glycolysis of poly (ethylene terephthalate) under microwave irradiation. Journal of Applied Polymer Science, 127(4), 2809-2815. http://dx.doi.org/10.1002/ app.37608.

8. Rusen, E., Mocanu, A., Rizea, F., Diacon, A., Calinescu, I., Mititeanu, L., Dumitrescu, D., & Popa, A.-M. (2013). Postconsumer PET Bottles Recycling II. PET depolymerization using microwaves. Materiale Plastice, 50(3), 201-207. Retrieved in 2015, July 07, from http://www.revmaterialeplastice.ro/pdf/ RUSEN%20E.pdf%203%2013.pdf 9. Chaudhary, S., Surekha, P., Kumar, D., Rajagopal, C., & Roy, P. K. (2013). Microwave assisted glycolysis of poly(ethylene

Polímeros, 28(1), 1-5, 2018

terephthalate) for preparation of polyester polyols. Journal of Applied Polymer Science, 129(5), 2779-2788. http://dx.doi. org/10.1002/app.38970.

10. Liu, N., Ma, Y., Shu, K., Wu, B., & Zhang, D. (2014). Catalysis investigation of PET depolymerization with bransted acidic ionic liquid under microwave irradiation. Advanced Materials Research, 893, 23-29. http://dx.doi.org/10.4028/www.scientific. net/AMR.893.23.

11. Yue, F. Q., Yang, H. G., Zhang, L. M., & Bai, X. F. (2014).

Metal-Containing ionic liquids: highly effective catalysts for degradation of poly(Ethylene Terephthalate). Advances in Materials Science and Engineering, 2014, 1-6. http://dx.doi. org/10.1155/2014/454756.

12. Yue, Q. F., Wang, C. X., Zhang, L. N., Ni, Y., & Jin, Y. X. (2011). Glycolysis of poly(ethylene terephthalate) (PET) using basic ionic liquids as catalysts. Polymer Degradation & Stability, 96(4), 399-403. http://dx.doi.org/10.1016/j. polymdegradstab.2010.12.020.

13. Aguado, A., Martínez, L., Becerra, L., Arieta-araunabena, M., Arnaiz, S., Asueta, A., & Robertson, I. (2014). Chemical depolymerization of PET complex waste: hydrolysis vs. glycolysis. Journal of Material Cycles and Waste Management, 16(2), 201-210. http://dx.doi.org/10.1007/s10163-013-0177-y.

14. Imran, M., Lee, K. G., Imtiaz, Q., Kim, Q. B., Han, M., Cho, B. G., & Kim, D. (2011). Metal-oxide-doped silica nanoparticles for the catalytic glycolysis of polyethylene terephthalate.

Journal of Nanoscience and Nanotechnology, 11(1), 824-828.

PMid:21446554. http://dx.doi.org/10.1166/jnn.2011.3201.

15. Wi, R., Imran, M., Lee, K. G., Yoon, S. H., Cho, B. G., & Kim, D. H. (2011). Effect of support size on the catalytic activity of metal-oxide-doped silica particles in the glycolysis of polyethylene terephthalate. Journal of Nanoscience and Nanotechnology, 11(7), 6544-6549. PMid:22121753. http:// dx.doi.org/10.1166/jnn.2011.4393.

16. Park, G., Bartolome, L., Lee, K. G., Lee, S. J., Kim, D. H., & Park, T. J. (2012). One-step sonochemical synthesis of a graphene oxide-manganese oxide nanocomposite for catalytic glycolysis of poly(ethylene terephthalate). Nanoscale, 4(13), 3879-3885. PMid:22592889. http://dx.doi.org/10.1039/ c2nr30168g.

17. Bartolome, L., Imran, M., Lee, G. K., Sangalang, A., Ahn, K. J., & Kim, D. H. (2013). Superparamagnetic γ-Fe2O3 nanoparticles as an easily recoverable catalyst for the chemical recycling of PET. Green Chemistry, 16(1), 279-286. http:// dx.doi.org/10.1039/C3GC41834K. 18. Balacianu, F. D., Nechifor, A. C., Bartos, R., Voicu, S. I., & Nechifor, G. (2009). Synthesis and characterization of Fe3O4 magnetic particles-multiwalled carbon nanotubes by covalent functionalization. Optoelectronics and Advanced Materials Rapid Communications, 3(3), 219-222. Retrieved in 2015, July 07, from https://oam-rc.inoe.ro/download.php?idu=665 Received: July 07, 2015 Revised: Mar. 21, 2016 Accepted: June 10, 2016

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ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.2412

O O O O O O O O O O O O O O O O

FT-IR methodology (transmission and UATR) to quantify automotive systems Ana Carolina Ferreira1, Milton Faria Diniz2 and Elizabeth da Costa Mattos1,2* Departamento de Química, Instituto Tecnológico de Aeronáutica – ITA, São José dos Campos, SP, Brazil Divisão de Química – AQI, Instituto de Aeronáutica e Espaço – IAE, São José dos Campos, SP, Brazil

1

2

*beth1.mattos@gmail.com

Abstract When using Fourier transform infrared spectroscopy (FT-IR) under the qualitative aspect for characterization of polymer blends, often a simple identification of each one of the existing polymers in the blend does not justify the material failure since different amounts of each component may result in different mechanical properties, which should be a possible cause for of material failure when applied to an automotive part. Thus, seeking for a better justification in the understanding of material failure analysis, a new quantitative FT-IR methodology was developed in the mid-infrared region (MIR), using the transmission techniques and universal attenuated reflectance for the determination of Acrylonitrile Butadiene Styrene (ABS) and polycarbonate (PC). Transmission mode was more suitable. The relative band (A831/A2237) was chosen for the preparation of the calibration curve that showed a 0.99% error methodology, which is within the FT-IR spectrometer accuracy limit (≤ 2%); therefore, it is accurate for the analysis of the system.

Keywords: automotive systems, MIR, polymer blends, quantification, transmission.

1. Introduction As known, the polymers exhibit thermal stability, resistance to chemical action, mechanical properties, among others, and are currently one of the most used materials, as external and internal components, in the automotive industry. Plastics have high reliability index and many advantages over traditional materials such as steel, aluminum and glass. About 100 kg of plastics are used inside and/or outside the vehicle[1].

In the European automotive industry, the plastics or thermoplastics materials contribute to 10% of the total weight of the vehicle, and about 41% of this material are made up of polypropylene (PP), 20% polyamide or nylon (PA), 14% ABS, 6% PC, 6% polyacetal (POM), 5% poly (butylene terephthalate) (PBT), 2% poly (methyl methacrylate) (PMMA), and other materials. In the American vehicle industry, 38% of plastic materials are inside the car, 29% in the body, 10% in the hood and 23% in the powertrain system and chassis.

The choice of polymer materials is at 47% PVC, 20% PP, 5% polyurethane, and other materials; the non-plastic ones correspond to 28%[2].

The advantages obtained from the use of plastics are related to the economy of fuel and production investments.

Furthermore, the possibility of design sophistication, the use of ways of less traditional solutions and increased safety drive the application of polymeric materials in automotive solutions. The disadvantages are: flammability, low impact resistance, deterioration by thermal and environmental action, etc. However, in accordance with the required specification of the material to be used, there may be a type of polymer specially produced to meet the requirements of use, overcoming a disadvantage found in a common plastic[1].

There are several types of polymers applied to the component parts of vehicles, such as the instrument panel,

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the bumpers, the upholstery, the carpets, the head and tail lamps, as well as in the door trim panels and in the roof.

Probably, in the future, polymers will be used in other places of such automotive systems[3].

In the automotive industry, some polymers are “enriched” by incorporation of loads and changes in mechanical and thermal properties by the “healing” process, making them engineering plastics[4].

Engineering plastics are stable materials for certain periods.

Therefore, they are used in applications where they can suffer mechanical, thermal, electrical, chemical or environmental stress. In general, these are more expensive than plastic “commodities”, due to a more elaborate manufacturing.

They are preferably chosen for their easy processability and flexibility in providing more complex designs with good dimensional stability and excellent resistance to chemical corrosion in hostile environments. The most commonly used polymers are: high molar mass polyethylene (UHMWPE), poly (methylene oxide) (POM), poly (ethylene terephthalate) (PET), PBT, PC, PA, and others[4].

The increasing use of polymeric materials by industries, aiming to replace several traditional materials, has attracted the attention of researchers in the discovery of new materials achieved through blends or polymer blends, in order to obtain better performance of the mechanical properties, lower cost/benefit and environmental impact. An alternative that meets these requirements is the preparation of blends, consisting of compatibilization of polymers with different characteristics. The major advantages of these materials are the range and versatility of their applications coupled with the ease of processing, enabling the production of diverse devices and making them incomparable with other materials[5].

Polímeros, 28(1), 6-14, 2018

FT-IR methodology (transmission and UATR) to quantify automotive systems One of the most important is the blend PC/ABS. This importance is due not only to the acquired characteristics, such as impact resistance and temperature, but also to good dimensional stability. It is widely used in the automotive industry as items of the panel, steering columns covers, chrome logos, internal housings etc.[5].

The virgin ABS, with an amorphous thermoplastic origin, is composed of acrylonitrile (AN) (20 to 30%), styrene (20 to 60%), the elastomeric phase consists of butadiene (20 to 30%). As described by Carvalho[6], it consists of two phases in which the SAN copolymer, composed of acrylonitrile and styrene, is the continuous phase (matrix), wherein the dispersed elastomeric phase is butadiene.

The butadiene rubber phase has grafted SAN (grafting) on its surface, which ensures compatibility between the two phases. The acrylonitrile provides thermal and chemical resistance, fatigue resistance, strength and stiffness; styrene provides ease of processing, gloss, hardness and rigidity; and butadiene provides ductility at low temperature, impact resistance, thermal stability and good surface finish.

The PC, a thermoplastic of amorphous origin, consists of long linear chains of polyesters of carbonic acid and phenols (phenyl) such as bisphenol A. The presence of phenyl group in the molecular chain and two methyl groups contributes to the rigidity of molecular PC. This rigidity has a large effect on the properties of PC, which contributes to the lack of mobility of the individual molecules, thus resulting in a good heat resistance and excellent impact resistance. For blends of PC/ABS, it is expected that the impact resistance is higher than that of the matrix component[7].

Typically the blend PC/ABS for vehicle applications has about 60 to 70% PC, since it is from this content that it is possible to perceive the earned properties in the blend.

Due to economic and technical reasons, the blend used is the one that has intermediate cost and properties. There are specific applications where the properties of the PC/ABS blends are enough to achieve the necessary features for a specific piece.

The properties of different PC/ABS blends are determined mainly by the type of PC content as well as the proportion of the acrylonitrile butadiene and styrene monomers present in the ABS, as shown in Figure 1.

Figure 1. Influence of co-monomers in ABS properties[8].

Polímeros, 28(1), 6-14, 2018

The impact resistance of PC/ABS is one of its main properties, and the type used ABS and PC content exerts a strong influence on this property[8].

Blends produced with high value materials, such as ABS and PC, allow to obtain products with a wide range of physical, chemical and mechanical properties. Thus ABS contributes to a better processability and lower cost of the blend basically due to its cost per kilogram being less than the cost of PC. However, PC provides good mechanical and thermal properties to the blend, which justifies its use.

These two materials have a strong chemical interaction, and are dependent on the percentage of the mixture of each component[7].

With the development of various polymers, there is also the need for the advancement of instrumental analysis techniques in order to determine the chemical structure of new materials and/or quantify them. As known, the FT-IR spectroscopy is one of the techniques that has merit for this purpose and has been successfully applied to various polymer systems in the group’s laboratories of the Divisão de Química (AQI) of the Instituto de Aeronáutica e Espaço (IAE), including the use of last-edge techniques with surface analysis (universal attenuated total reflectance - UATR) in wide spectral range (mid-infrared, MIR, near-infrared, NIR, and others)[9-11].

The opportunity to develop a methodology applied to polymer blends, used in the automotive sector, is still not very explored; therefore, in the literature, FT-IR studies could be found for other types of materials for this sector, but not for the proposition of the present research.

Ruschel et al. reported it was possible to confirm the usefulness of this conventional technique, in combination with the chemometric tools HCA and PCA for diesel and biodiesel oil blends classification differentiating them from their infrared spectra even though these mixtures are composed of various types of biodiesel from three different raw materials soybean oil, residual oil and hydrogenated vegetable fat for frying and two alcoholic routes: methyl and ethyl[12]. In the study of Tahmassebi et al., it was analyzed the performance of automotive coatings, using different techniques, among which the infrared spectroscopy for monitoring the oxidation, applying the characteristic functional groups, when the ink is exposed to weathering test[13].

Therefore, given the presented scenario, the interest of the automobile company in the development of methodologies to assist in solving problems occurring in the field to manufactured using blends and the fact that studies including quantitative analysis by means of FT-IR technique transmission and reflection are mentioned in smaller numbers in the literature, there has been a great interest in the development of a quantitative method for blends of the type PC/ABS, which should lead to troubleshooting in the field, when the blend is applied to the workpiece, but not in the appropriate proportions of each material.

To achieve this purpose, the present study evaluates the applicability of FT-IR transmission and reflection (latest generation, as UATR) absorption spectroscopy, with existing laboratory facilities in AQI-IAE, for the identification and quantification of the polymer base, used in different automotive industrial formulations.

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Ferreira, A. C., Diniz, M. F., & Mattos, E. C.

2. Materials and Methods 2.1 Samples Different polymer blends PC/ABS were kindly prepared and provided by SABIC company. The donated samples were named: 100% PC resin LEXAN™ 123R-112, 100% ABS resin CYCOLAC™ MG37 EPX NA100, 30% PC/70% ABS, 50% PC/50% ABS, 70% PC/30% ABS. In addition, using the pure samples, 100% PC resin LEXAN™, 100% ABS resin CYCOLAC™ MG37 EPX NA 100, Mackenzie gently prepared the blends 40% PC /60% ABS, 80% PC /20% ABS. For the preparation of the blends 40% PC/60% ABS and 80% PC/20% ABS, the previously weighed pure materials in their concentrations were mixed using the equipment Mix - MH Equipamentos Ltda., with subsequent extrusion of the material.

2.2 Methodology The samples were analyzed in PERKINELMER SPECTRUM ONE FT-IR spectrometer (resolution 4 cm-1, gain 1, range 4000 to 550 cm-1, 20 scans) by means of reflection techniques, using accessory UATR and transmission (resolution 4 cm-1, gain 1, range 4000 to 400 cm-1, 20 scans).

Using previously prepared mixtures in the following concentrations: 30% PC/70% ABS, 40% PC/ 60% ABS, 50% PC/50% ABS, 70% PC/30% ABS, 80% PC/20% ABS, the calibration or analytical curve was built.

The films were prepared by dissolving in chloroform (five aliquots) being called cast films in accordance with the sample preparation techniques for IR analysis.

The preparation procedure of cast films of concentrations of 30% PC/70% ABS, 40% PC/60% ABS, 50% PC/50% ABS, 70% PC/30% ABS, and 80% PC/20% ABS was as follows: each of the above blends was weighed in an amount equal to the total weight 0.05g. We dissolved each of the blends in 15 mL of chloroform under stirring and heating. After the total dissolution of the material, samples were placed in Petri dishes, and 5 mL of chloroform were used to the beaker wash to ensure all the material was transferred to the Petri dishes and these were placed on a flat surface, waiting to complete evaporation of the chloroform in order to obtain a

cast film. For each sample, five aliquots were analyzed at the locations marked as 1, 2, 3, 4 and 5, as shown in Figure 2.

Analysis by UATR, the samples were analyzed by placing them in contact with the surface of the ZnSe diamond crystal, with application of torque (120 N). For analysis by transmission, the cast film was placed in the beam path, in marked areas.

The data were calculated according to Hórak and Vítek[14] form adopted in earlier work of the group and it was successfully carried out involving quantitative IR analysis[15-18]. For each sample, five aliquots were analyzed and, from the absorbance values, the median was calculated (μ). The standard deviation (σˆ µˆ ) of the median absorbance is calculated according to Equation 1: σˆ µˆ = σˆ

n

(1)

Where σˆ is the standard deviation and n is the number of measures. σˆ is given by Equation 2: = σˆ K R × R (2)

Where KR is the coefficient for the calculation of the average standard deviation from the variation range of values (for 5 experiments, KR = 0.430); and R is the difference between the largest and the lowest value of absorbance (Xn – X1).

The relative error for each sample analyzed was determined using Equation 3:  σˆ  = Relativeerror ( % )  µˆ µ  ×100 (3)  

For the methodology of the calculation of error, it was adopted the median value[14] of the errors, as performed in previous studies[15-18].

The choice of the baseline, analytical and reference peak was made according to the lowest relative error and the largest correlation coefficient (R) in the calibration curves, as in previous work[15].

Figure 2. Cast films obtained after solvent evaporation (marked locations were analyzed by IR transmission and UATR).

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Polímeros, 28(1), 6-14, 2018

FT-IR methodology (transmission and UATR) to quantify automotive systems

3. Results and Discussion 3.1 FT-IR characterization by transmission of the main bands observed in the blend of ABS and PC As the transmission method has a higher intensity of each characteristic band of each polymer, it was decided to place each of these for subsequent choice of analytical bands for the study. The absorption characteristics of the ABS polymer are (cm-1): 3010-3110: axial deformation or aromatic C-H stretch, 2237: axial deformation C≡N, 1602: axial strain C ═ N and angular deflection of C ̶ C of the aromatic ring, 1506: angular deformation ArCH, 1453: asymmetric angular deformation CH3, 1365: symmetrical angular deformation CH3, 966: angular deformation C ═ C, 735-765: angular deformation, ArCH (mono-substituted) and 697: aromatic C-H out of plane angular deformation[19].

The PC characteristics are absorptions at (cm-1): 3010-3110: axial deformation aromatic C-H, 1775: axial deformation C═O, 1230, 1164, 1081 and 1015: axial deformation in C-O-C, 831: angular deformation aromatic C-H (para replacement)[19]. Figure 3 includes the FT-IR spectra in the MIR region of the pure polymers studied.

It can be observed through the bands indicated in Figure 4 that as there are increasing PC concentrations, the intensities of the bands at 1775 and 831 cm-1 increase and the absorption found at 2237cm-1 decreases associated with the corresponding decrease in acrylonitrile content, suggesting that it is possible to perform the determination of the levels of the blend by FT-IR because the analyzed system obeys the Lambert-Beer law[19], namely:

given wavelength or wavenumber or, in other words, how strongly a substance absorbs radiation at a specific frequency; b = thickness; c = concentration[19].

Therefore, for this study, based on the intensities and different positions of wave number for each polymer, the mentioned bands are chosen for the determination of contents of PC and ABS in the blend.

One of the causes of errors in IR quantitative analysis is the variation of intensity of the same concentration samples, due to thickness variations of these materials analyzed, and a mathematical artifice used in IR spectroscopy is to divide the values of the intensities of absorptions constituting the band on (A1/A2) as: A1 a1× b × c1 (5) = A2 a 2 × b × c 2

A = a × b × c (4)

where A = absorbance, or absorption; a = molar absorptivity or molar extinction coefficient (characteristic band), the capacity of one mole of substance for absorbing light at a

Figure 3. Spectra FT-IR (MIR - Transmission) of pure polymers.

Figure 4. Spectra FT-IR (MIR - Transmission) of the polymer blend film.

Polímeros, 28(1), 6-14, 2018

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Ferreira, A. C., Diniz, M. F., & Mattos, E. C. Therefore, to eliminate the effect of the thickness in the calculation of the intensity of absorption of this determination, the analytical bands were used (A1 and A2) of each polymer as reference bands from one another, thereby composing a relative band PC/ABS. For the application of the Lambert-Beer law, the absorbance data obtained were placed on a function of the relative concentration[20].

3.2 Choice of analytical bands of ABS and PC, UATR method Just as was done in the transmission method, we studied the determination by the reflection method, with UATR accessory. Remember that a slight difference may occur in the position of each of the analytical bands in these different methods for collecting the infrared spectra.

The absorption at 697 cm-1 was chosen as the analytical band for determining the content of ABS, and those found at 1770 and 829 cm-1 for determining the content of PC in the blend, all indicated in Figure 5. These bands were chosen as analytical, therefore, it can be seen that the increase in the intensity of the band at 697 cm-1 is related to the increase in the ABS content, as well as at the bands of 1770 and 829 cm-1, with the increase in PC content in the blend. The band of 2237 cm-1, referring to the ABS, did not show good response to this method, because of its low intensity, so it was not chosen as analytical band.

864‑793 cm-1 for the band at 829 cm-1, with similar methodology for baseline evaluation used by Rodrigues et al.[17]. As for eliminating the effect of the thickness, the reference band used in this case was the analytical band of ABS, the band at 697 cm-1. The use of reference band, to compose a relative band, improves accuracy of the methodology[17].

Table 2 shows the analytical bands, the chosen baselines and results as relative error in the methodology and correlation coefficients R. Evaluating Table 2, the bands at 829 and 697 cm-1, respectively, for PC and ABS, show the set of lower data error (3.20%) and the correlation coefficient (0.99).

3.4 Choice of analytical bands of ABS and PC, transmission method As previously mentioned, for this study, based on the intensities and different positions of wave number for each polymer, the absorption at 2237 cm-1 was chosen as the analytical band to determine the ABS content, and two possibilities of analytical bands, 1775 and 831 cm-1, to determine the content of PC in the blend, all already mentioned in Figure 4.

The baselines adopted for the measurements are shown in Table 3. Likewise, as has been previously reported for Table 1. Baselines for analytical band ABS and PC. Polymer type ABS PC

3.3 Choice of the reference band, UATR method Table 1 shows the analytical bands adopted and their respective baselines. The absorption at 697 cm-1 was at baseline 718-660 cm-1, 1840-1694 cm-1 for the band 1770 cm-1, and

Analytical band (baseline) cm-1 697 (718-660) 1770 (1840-1694) 829 (864-793)

Figure 5. Spectra FT-IR (MIR - Reflection - UATR) of the polymer blend film.

Table 2. FT-IR data errors in the methodology and correlation coefficient of different analytical bands analyzed for the blend PC/ABS. Analytical band (baseline) cm-1 1770 (1840-1694) C═O 829 (864-795) ArCH (para replacement)

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Analytical band (baseline) cm-1 697 (718-660) ArCH 697 (718-660) ArCH

Relative error in the methodology 7.10 3.20

Correlation coefficients R 0.99 0.99

Polímeros, 28(1), 6-14, 2018

FT-IR methodology (transmission and UATR) to quantify automotive systems the UATR method, these bands were chosen as analytical, therefore, it can be seen that the increase in the intensity of the band at 2237 cm-1 is related to the increase in the ABS content, as well as in the bands 1775 and 831 cm-1, with the increase in PC content in the blend.

Where y is the median value of A831/A2237 example, the relative concentration (PC concentration/ABS concentration) in the polymer blend.

3.5 Choice of the reference band transmission method

Until then, it was considered the correlation coefficient R with respect to the relative concentration, aiming to find a more precise methodology according to the analyzed system.

In the next paragraph, the concentration of polycarbonate will be taken into account and not the relative concentration.

Table 3 refers to the adopted analytical bands and their respective baselines. The choice of the best set of analytical bands occurred after evaluating the accuracy in measuring the intensity of the band.

Table 4 shows the analytical bands analyzed, chosen baselines and results as relative error in the methodology and correlation coefficient R. Bands at 831 and 2237 cm-1, respectively, for PC and ABS, showed the lowest error (0.99%), the and highest correlation coefficient (0.96). Considered a best result compared to other pairs of bands of the analytical methods previously assessed, these absorptions were adopted as relative band (A831/A2237) to study transmission.

Table 5 shows the results obtained by applying Equations 1, 2 and 3 for the relative band (A831/A2237) taking into account the relative concentration, in an attempt to achieve higher precision. The error methodology, which is the median of the relative error, is 0.99, within the limits of measurement accuracy (≤2%).

3.7 Choice of analytical band ABS and PC, transmission method, evaluation of polycarbonate concentration

The idea is based on the fact that there are several types of ABS polymers with different concentrations of each of the monomers present in the blend, and the content of each monomer will vary according to the application.

It is important to note that the polymer ABS, which was kindly supplied by SABIC, presents 100% of ABS resin of the type CYCOLAC™ MG37 EPX NA 100, wherein the amount of each monomer is considered confidential information for supplier.

Therefore, for this method to be applied in any type of ABS, it was decided to develop the construction of a calibration curve taking into account the concentration

3.6 Calibration curve obtained by transmission Figure 6 shows the analytical transmission curve (A831/A2237) versus relative concentration (PC concentration/ABS concentration). From the analytical curve, Equation 6, the following correlation (R = 0.96) is proposed: = y 2.451x + 1.260 (6)

Table 3. Baselines for analytical bands of ABS and PC. Polymer type ABS PC

Analytical band (baseline) cm-1 2237 (2280-2184) 1775 (1840-1690) 831 (864-791)

Figure 6. Relative absorbance values (A831/A2237) obtained by transmission versus relative concentration.

Table 4. FT-IR data relative errors in the methodology and correlation coefficient of different analytical bands analyzed for the blend PC/ ABS by evaluating the relative concentration.

Analytical band (baseline) cm-1 1775 (1840-1690) C═O 831 (864-791) ArCH (para replacement)

Analytical band (baseline) cm-1 2237 (2280-2184) C≡N 2237 (2280-2184) C≡N

Relative error in the methodology % 1.57 0.99

Correlation coefficient R 0.94 0.96

Table 5. FT-IR data of the median, standard deviations average, relative errors and error in the chosen relative band A831/A2237. [ ] PC 30 40 50 70 80

[ ] Relative

[PC]/[ABS] 0.43 0.67 1.00 2.33 4.00

Polímeros, 28(1), 6-14, 2018

Median µ 1.739 2.204 3.921 8.808 10.089

Standard deviation

(σˆ µˆ )

Relative error %

Error in the methodology %

0.017 0.022 0.061 0.141 0.099

0.99 0.92 1.55 1.60 0.98

0.99

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Ferreira, A. C., Diniz, M. F., & Mattos, E. C. of the PC, and not the relative concentration (PC/ABS).

As the best results were already cited in Table 4, these are the values used for the development of this methodology.

Table 6 shows the analyzed analytical bands, chosen baselines, results of relative errors in the methodology and correlation coefficients R. Bands at 831 and 2237 cm-1, respectively, for PC and ABS are also those with the lowest error (0.99%) and the highest correlation coefficient (0.99). Considered a best result compared to other pairs of bands of the analytical methods previously assessed, these absorptions were adopted as relative band (A831/A2237) to study transmission.

Table 7 contains the results obtained by applying Equations 1, 2 and 3 for the relative band (A831/A2237), taking into account the PC concentration. Remember that the values of the median, average standard deviation and relative error are the same as already calculated and shown in Table 5. The error methodology, which is the median of the relative error, is 0.99, within the limits of precision instrument (≤2%).

3.8 Calibration curve obtained by transmission, evaluation of polycarbonate concentration

A and 50% PC/50% ABS for sample B. These samples were prepared using the same materials applied to construct the calibration curve. Another test sample, sample C, was prepared with the following concentration: 50% PC/50% ABS, this ABS is of the type NovodurTM P2MC, material kindly donated by Styrolution company and the PC is of the same type used above (Resin LEXANTM). With Equations 6 and 7, the amount of PC concentrations was calculated using the methodology of relative concentration and PC concentration.

Using Equation 6, it was calculated the value of the PC concentration, being y the median relative analytical band (A831/A2237) obtained in the analysis, and x is the value (%) of relative concentration (PC concentration/ABS concentration).

For the calculation of ABS and PC concentrations, it was used Equation 8: X=

[ PC ] ⇒ PC = [ ] [ ABS ]

X [ ABS ] (8)

Substituting Equation 8 into Equation 9, it is calculated the value of the ABS concentration. The percentage (%) of PC was calculated by difference for a total of 100%. The values found are shown in Table 8.

Figure 7 shows the analytical transmission curve (A831/A2237) versus PC concentration. From the analytical curve, Equation 7, the following correlation (R = 0.99) is proposed: = y 18.149 x + 4.408 (7)

Where y is the median value of A831/A2237 and x is the PC concentration in the polymer blend.

3.9 Calibration curve test for transmission technique According to what has been stated above, the bands at 831 and 2237 cm-1, respectively, for PC and ABS, present the lowest error and showed the highest correlation coefficient, using the relative concentration and PC concentration.

Therefore, the two showed methods will be used to assess the test sample. This is a verification procedure of the methodology, where two samples were analyzed with the following concentrations: 70% PC/30% ABS for sample

Figure 7. Relative absorbance values (A831/A2237) obtained by transmission versus PC concentration.

Table 6. FT-IR data errors in the methodology and correlation coefficient of different analytical bands analyzed for the blend PC/ABS, evaluation of polycarbonate concentration.

Analytical band (baseline) cm-1

Analytical band (baseline) cm-1

Relative error in the methodology

1775 (1840-1690) C═O 831 (864-791) ArCH (para replacement)

2237 (2280-2184) C≡N 2237 (2280-2184) C≡N

% 1.57 0.99

Table 7. FT-IR data of the average deviations and errors in the chosen relative band A831/A2237.

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[PC]

ˆ µˆ ) Standard deviation (σ

Relative error %

30 40 50 70 80

0.017 0.022 0.061 0.141 0.099

0.99 0.92 1.55 1.60 0.98

Correlation coefficient R 0.98 0.99

Error in the methodology %

0.99

Polímeros, 28(1), 6-14, 2018

FT-IR methodology (transmission and UATR) to quantify automotive systems Table 8. Calculation of the concentrations of PC/ABS of the samples from tests A, B and C by using a relative concentration.

Sample A B C

Concentration 70% PC/30% ABS 50% PC/50% ABS 50% PC/50% ABS

PC concentration 75.5 52.3 51.1

ABS concentration 24.5 47.7 48.9

Table 9. Calculation of the concentrations of the PC/ABS of the samples from tests A, B and C by using the PC concentration.

Sample A B C

Concentration 70% PC/30% ABS 50% PC/50% ABS 50% PC/50% ABS

100% (9) [ PC ] + [ ABS ] =

Using Equation 7, it was calculated the value of the PC concentration, being y the median relative analytical band (A831/A2237) obtained in the analysis, and x is the value (%) of PC concentration. The percentage (%) of ABS was calculated by difference for a total of 100%. The values found are shown in Table 9.

Although both methods have shown good accuracy, the one which takes into account the relative concentration showed better results in comparison with PC concentration when applied to the calibration curve of the test, even with a different type of ABS used.

4. Conclusion This study demonstrated the application of FT-IR spectroscopy in the MIR region for the characterization and quantification of automotive blends of PC/ABS using two methodologies: UATR and transmission. Some relative bands were evaluated using both methods, while the A831/A2237 showed better results, that is, the lowest relative error and the highest correlation coefficient, when applied to the transmission method. As there are many types of ABS polymers with different concentrations of each of the monomers present in the blend, two calibration curves were constructed using the relative concentration and also the PC concentration. Both curves proved useful to characterize and quantify the content of each polymer present in the polymer blend PC/ABS, with a better accuracy for the observed found in the relative concentration.

The methodological error found in MIR methodology - Transmission (0.99%) for the two calibration curves used is within the accuracy limit of FT-IR spectrometer (≤2%), so the methodology is accurate.

5. References 1. Hemais, C. A. (2003). Polímeros e a indústria automobilística.

Polímeros: Ciência e Tecnologia, 13(2), 107-114. http://dx.doi. org/10.1590/S0104-14282003000200008.

2. Cordebello, F. S. (2003). Polímeros do futuro – tendências e oportunidades: palestras técnicas (II). Polímeros: Ciência e Tecnologia, 13(1), e4-e43. http://dx.doi.org/10.1590/S010414282003000100003.

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PC concentration 72.8 46.0 45.3

ABS concentration 27.2 54.0 54.7

3. Neto, N. J. R. (2012). A evolução dos polímeros na indústria automobilística (Term paper). Sorocaba: Faculdade de Tecnologia do Estado de São Paulo – FATEC. Retrieved in 2014, April 16, from //fatecsorocaba.edu.br/principal/pesquisas/nuplas/ dissertacoes/TCCs1sem2012/TCC_Nelson_Joao.pdf 4. Dornelles, A. M. L. F., & Atolino, W. J. T. (2009). Plásticos de engenharia: seleção eletrônica no caso automotivo. São Paulo: Artliber Editora.

5. Novaes, I. C. (2010). Estudo das propriedades físico-mecânicas da blenda ABS/PC (Term paper). São Paulo: Faculdade de Tecnologia do Estado de São Paulo – FATEC. Retrieved in 2014, March 11, from http://www.scribd.com/doc/221425914/ Acrilonitrila-Butadieno-Estireno-Estudo-Propriedas FisicoMecanica 6. Carvalho, C. (2009). Reciclagem primária de ABS: propriedades mecânicas, térmicas e reológicas (Master’s dissertation).

Universidade do Estado de Santa Catarina, Joinville.

7. Candido, L. H. A. (2011). Estudo do ciclo de reciclagem de materiais em blendas acrilonitrila butadieno estireno/ policarbonato (Doctoral thesis). Universidade Federal do Rio Grande do Sul, Porto Alegre.

8. Simielli, E. R., & Santos, P. R. (2010). Plástico de engenharia, principais tipo e sua moldagem por injeção. São Paulo: Artiliber.

9. Santos, R. P., Oliveira, M. S., Mattos, E. C., Diniz, M. F., & Dutra, R. C. L. (2013). Study by FT-IR technique and adhesive properties of vulcanized EPDM modified with plasma. Journal of Aerospace Technology and Management, 5(1), 65-74. http:// dx.doi.org/10.5028/jatm.v5i1.162.

10. Sanches, N. B., Diniz, M. F., Alves, L. C., Dutra, J. C. N., Cassu, S. N., Azevedo, M. F. P., & Dutra, R. C. L. (2008). Avaliação da aplicabilidade de técnicas FT-IR de reflexão (UATR) e de transmissão para a determinação do teor de acrilonitrila (AN) em NBR. Polímeros. Ciência e Tecnologia, 18(3), 249-255. http://dx.doi.org/10.1590/S0104-14282008000300011.

11. Nogueira, L. M., Dutra, R. C. L., Diniz, M. F., Pires, M., Evangelista, M., Santana, F. A., Tomasi, L., Santos, P., & Nonemacher, R. (2007). Avaliação da aplicabilidade de técnicas MIC/FT-IR/DSC para caracterização de filmes multicamadas.

Polímeros: Ciência e Tecnologia, 17(2), 158-165. http://dx.doi. org/10.1590/S0104-14282007000200015.

12. Ruschel, C. F. C., Huang, C. T., Samios, D., & Ferrão, M.F. (2014). Análise exploratória aplicada a espectros de reflexão total atenuada no infravermelho com transformada de Fourier (ATR-FTIR) de blendas de biodiesel/diesel. Quimica Nova, 37(5), 810-815. http://dx.doi.org/10.5935/0100-4042.20140130.

13. Tahmassebi, N., & Moradian, S. (2004). Predicting the performances of basecoat/clearcoat automotive paint system by the use of adhesion, scratch and mar resistance measurements.

Polymer Degradation & Stability, 83(3), 405-410. http://dx.doi. org/10.1016/j.polymdegradstab.2003.09.002.

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Ferreira, A. C., Diniz, M. F., & Mattos, E. C. 14. Hórak, M., & Vítek, A. (1978). Interpretation and processing of vibrational spectra. New York: John Wiley & Sons.

15. Mattos, E. C., Moreira, E. D., Dutra, R. C. L., Diniz, M. F., Ribeiro, A. P., & Iha, K. (2004). Determination of the HMX and RDX content in synthesized energetic material by HPLC, FT-MIR, and FT-NIR spectroscopies. Quimica Nova, 27(4), 540-544. http://dx.doi.org/10.1590/S0100-40422004000400005.

16. Siqueira, S. H. S., Diniz, M. F., & Dutra, R. C. L. (2008).

Determinação por espectroscopia nas regiões MIR/NIR do teor de NCO em adesivos poliuretânicos. Polímeros: Ciência e Tecnologia, 18(1), 57-62. http://dx.doi.org/10.1590/S010414282008000100012.

17. Rodrigues, V. C., Diniz, M. F., Mattos, E. C. & Dutra, R. C. L. (2014). Quantificação por NIR/MIR de resina poliuretânica em misturas binárias com nitrocelulose, utilizadas em tintas.

Polímeros: Ciência e Tecnologia, 24(3), 367-372. http://dx.doi. org/10.4322/polimeros.2014.027.

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18. Damazio, D., Diniz, M. F., Mattos, E. C., & Dutra, R. C. L. (2014). Determinação por FT-IR de transmissão e reflexão (UATR) de etileno e propileno em EPDM. Polímeros: Ciência e Tecnologia, 24(6), 703-710. http://dx.doi.org/10.1590/01041428.1536.

19. Smith, A. L. (1979). Applied infrared spectroscopy. New York: John Wiley & Sons.

20. Mattos, E. C. (2007). Caracterização e quantificação por meio de técnicas FT-IR, HPLC e TG de polímeros utilizados em composições de explosivos plásticos (Doctoral thesis).

Instituto Tecnológico de Aeronáutica, São José dos Campos.

Received: Nov. 09, 2015 Revised: May 24, 2016 Accepted: June, 29, 2016

Polímeros, 28(1), 6-14, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.07016

Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite Elilton Rodrigues Edwards1*, Silvia Sizuka Oishi2 and Edson Cocchieri Botelho3 Department of Exact Sciences and Technology, Universidade Estadual de Santa Cruz – UESC, Ilhéus, BA, Brazil 2 LAS, Instituto Nacional de Pesquisas Espaciais – INPE, São José dos Campos, SP, Brazil 3 Department of Materials and Technology, Universidade Estadual Paulista – UNESP, Guaratinguetá, SP, Brazil

1

*eredwards@uesc.br

Abstract In this study, the chemical interaction between functionalized carbon nanotuboes with carboxyl groups (CNT-f) and the subsequent addition of furfuryl alcohol (FA) and mixture with poly(furfuryl alcohol) (PFA) resin was evaluated.

The FA with CNT-f was mixed in PFA resin to facilitate the chemical interaction of CNTs. The morphological and chemical interaction were studied by Transmission Electron Microcopies (MET), FTIR analyses, Raman Spectroscopy, viscosimetry and X-ray photoelectron spectroscopy (XPS). It was observed that a chemical interaction occurs through the opening of the hydroxyl polymer chain with a subsequent output of one water molecule. This interaction was evident from the FTIR and XPS data of the PFA composites. In this way, the mixture of functionalized carbon nanotubes with carboxyl groups in the FA, before adding this reinforcement into the PFA resin, can be considered a good procedure in order to obtain an appropriate chemical interaction between the CNT and PFA resin.

Keywords: nanostructured composite, chemical properties, surface analysis, cure reaction.

1. Introduction Poly(furfuryl alcohol) (PFA) is a thermosetting resin of furan class which has gained great importance mainly due to it being obtained from renewable resources[1,2]. Nowadays, this resin has a wide range of applications such as adhesives, glassy carbon nanoporous, polymer nanocomposites, etc[3,4].

Many studies have been undertaken to develop thermoplastic and thermosetting polymer composites with multiwall carbon nanotubes (MWCNT) as the reinforcing element[5,6].

According to the literature[7-10], by introducing small amounts of carbon nanotubes (CNTs), the mechanical, electrical and thermal properties of composite materials can be improved. However, it is generally known that CNTs are not compatible with most solvents available on the market because of the chemical inertness. In addition, it is difficult to obtain a homogeneous solution, resulting in poor dispersion capability of CNT into polymeric resins and weak interfacial interactions inside composite materials.

The mechanical and electrical properties of a polymer composite with CNT reinforcement depends on the dispersion and good chemical interaction between CNT and polymer matrix[7,8]. The literature[7-10] includes several possible mechanisms of polymerization of furfuryl alcohol with different types of catalysts, but until now there is no understanding about the chemical interaction between carbon nanotubes and PFA. In this study, the evaluation of the chemical interaction between functionalized CNT and PFA resin cured with p-toluene sufonic acid (PTSA) is presented. PFA composites were manufactured with 0 and 0.5, 1.0 and 2.0 wt%

Polímeros, 28(1), 15-22, 2018

of functionalized CNT. The CNTs and composites of PFA/functionalized CNT were characterized using XPS, transmission electron microscopy (TEM), viscosimetry, Raman and FTIR spectroscopies. From these results, a mechanism of chemical interaction between CNT and PFA was proposed.

2. Materials and Methods 2.1 Materials Multiwalled carbon nanotubes (MWCNT) were obtained from the pyrolysis of a mixture of camphor and ferrocene into a quartz tube at 850 °C[11]. This mixture was evaporated at 200 °C into a quartz tube in a tube furnace with a 200 sccm flow of inert gas (N2). By using this process, the growth rate of CNT was 15 μm/min. The CNT were produced with an outside diameter ranging from 50-100 nm and a length of ~100 μm. Poly(furfuryl alcohol) (PFA) resin was obtained from the polymerization of furfuryl alcohol (FA) using a diluted solution of sulfuric acid as a catalyst in the following proportion [furfuryl alcohol]/[acid solution] = l40.

The reaction occurred over one hour and was performed at an initial temperature of 32 °C. The final viscosity of the resin was about 265 mPa.s and the moisture was less than 1.0 wt%.

2.2 Purification and functionalization processes Purification of the MWCNT was performed using conventional acid treatments with a non-oxidative process using concentrated HCl (36 wt%) that was sonicated in an

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O O O O O O O O O O O O O O O O O

Edwards, E. R., Oishi, S. S., & Botelho, E. C. ultrasound bath for 5 h. The MWCNT were washed and filtered with a Millipore membrane (0.45 μm pore size) and dried in a vacuum oven at 100 °C for 12h. The functionalization process was performed using oxidative treatment with a mixture of H2SO4:HNO3 (3:1) under reflux at a temperature of between 45 °C and 50 °C for 5h in order to add carboxylic group over the CNT walls. This material was washed until it had a neutral pH, filtered and dried in a vacuum oven at 100 °C for 12h.

The mixture (FA+CNT-f) was mixed with 10g of PFA resin and sonicated again with an ultrasonic probe for 4 mins.

In both situations the temperature was controlled with an ice bath (see Figure 1). PTSA was used as a catalyst for the PFA cure at a proportion of 5.0 wt%. The composite was cured in a mold of silicon at 50 °C, 70 °C, 90 °C, 110 °C, 130 °C for 2 h in each temperature in an oven, model VUK/UV 55.

Cured PFA without CNT was also obtained for comparison.

2.3 Nanostructured composite manufacturing

Multiwall carbon nanotubes were characterized by transmission electron microscopy (TEM) using a Philips CM 120 microscope in order to evaluate the surface integrity after the oxidative functionalization process used in this study. These analyses were compared with the TEM results obtained for the purified material with HCl. Analysis

The nanostructured composite was processed with 0.5, 1.0 and 2.0 wt% of functionalized CNT into 5 mL of FA and sonicated for 4 mins in an ultrasonic probe. The wt% of CNT was determined from the composite mass without CNT [(FA alcohol) + (PFA resin) cured with PTSA].

2.4 Characterization

Figure 1. Synthesis rote for fabrication of composite of FPA resin with carbon nanotube functionalized.

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Polímeros, 28(1), 15-22, 2018

Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite of the high resolution scanning electron microscopy SEM (Mod. JEOL 7500) was also performed on a cross section of the fractured composite specimen reinforced with functionalized CNT. Raman spectroscopy was performed using a Renishaw 2000 system equipped with an Ar laser (514.5 nm), ranging from 1000 to 3500 cm-1, in order to verify the integrity of the CNT powder after each treatment, based on the relative intensity of the D and G band, (ID/IG)[12]. A study based on X-ray photoelectron spectroscopy (XPS) was performed to evaluate the insertion of carboxylic group onto the CNT walls. Additionally, XPS analyses were conducted using a commercial spectrometer (Model UNI-SPECS UHV).

The MgKα line used was hν=1253.6 eV and the analyzer pass energy was set up to 10 eV. The inelastic background of the C1s, O1s and electron core-level spectra was removed using Shirley’s method. FTIR analyses were performed in a spectrometer from PerkinElmer Instruments, Spectrum 100 model, using the universal attenuated total reflectance (UATR) technique.

3. Results and Discussions Figure 1 shows a schematic figure of the polymerization analysis between the functionalized MWCNT and poly(furfuryl alcohol). A chemical analysis the polymerization between the furfuryl resin polymer and functionalized MWCNT was performed.

Figure 2a shows a TEM image of the as-obtained CNTs. In this figure, the presence of iron particles into the tube in the form of small spheres can be observed. The particles of iron are derived from the ferrocene precursor used in the manufacturing process of carbon nanotubes. Figure 2b shows an image of purified CNT with concentrated HCl stored for 5h in an ultrasonic bath. The use of concentrated HCl shows that CNT both internal and external impurities, such as iron particles, are removed. A complete study in this regard was published in the references[13]. Figure 2c shows an image of CNT functionalized with H2SO4:HNO3 (3:1), which is a strong oxidative acid. This acid can insert a great amount of carboxylic groups onto CNT walls, however prolonged use can destroy their walls[13]. Some authors have also reported a process of exfoliation on the CNT walls and consequent reduction in wall thickness when using oxidative acids[12,14].

Figure 3a shows an image of the PFA composite with 2 wt% of CNT-f. This specimen was fractured to expose the CNTs in the material. The captured image shows the cross section of the fractured region in the composite. It is very difficult to expose the CNTs in this material because its morphology contains regions with overlapped layers in which the CNTs are wrapped, consequently only a few CNTs are exposed after fracturing. Figure 3b shows the surface with higher magnification containing carbon nanotubes (with an arrow).

Figure 4 shows the Raman spectra results from the neat (a), purified (b) and functionalized (c) carbon nanotubes. The band at 1352 cm-1 (D band) represents the disordered structure of carbon while G band at 1584 cm-1 corresponds to graphite in-plane vibrations with E2g symmetry. ID/IG intensity ratio is useful to estimate the degree of organization in graphitic materials. A higher ID/IG intensity ratio for neat CNT reveals Polímeros, 28(1), 15-22, 2018

Figure 2. TEM images of: (a) CNT-as-obtained; (b) purified with HCl-concentrated and (c) functionalized with oxidative acid H2SO4-HNO3.

a high degree of structural disorder (amorphous carbon).

For purified CNT and CNT-f, a decrease in the D band and an increase in the G band is observed with a higher graphitic ordering after the functionalization. The higher intensity of the G’ band at 2706 cm-1 for CNT-f is indicative of a more ordered structure, which indicates that amorphous carbon was eliminated and the integrity of the CNT was maintained after functionalization.

Figure 5 shows the FTIR analysis in PFA resin synthesized in our laboratory. The bands at 732, 1150 and 1505 cm-1 correspond to furan ring. The band at 1010 cm-1 17/22 17

Edwards, E. R., Oishi, S. S., & Botelho, E. C.

Figure 3. (a) SEM composite of PFA resin cured with CNTs functionalized (arrows pointed to the CNTs) and (b) shows the surface with higher magnification.

corresponds to the νC-O of furan ring. The band at 1218 cm-1 is attributed to C-O bonds from the alcohol or C-O-C of furan ring (νC‑OH, νC-O-C). The bands of the conjugated C=C species arise in 1355cm-1and 1561 cm-1. The stretching of the link -CH2-CO- emerges at 1420cm-1. The stretching at 1713cm-1 is related to acetone or aliphatic diketone (νC=O). The band at 2935 cm-1 suggests the presence of methyl groups and the band at 3120 cm-1 corresponds to C3 and C4 carbon. The position at 3413 cm-1 corresponds to OH stretch (νO-H)[15-19].

Figure 4. Raman spectra results: (a) neat CNT; (b) purified CNTs and (c) functionalized CNTs with H2SO4:HNO3.

Figure 6a shows the FTIR spectra of cured PFA and PFA composites with 0.5, 1.0 and 2.0 wt% of functionalized CNTs. Comparing neat composite with the composites containing different percentages of CNT-f, the band at 730 cm-1 changes to a dominance of 792 cm-1, which is related to the reaction progress. Thus, the presence of CNT-f increases the degree of polymerization in these samples[19,20].

The band at 1094 cm-1 is attributed to the (C-C-C) bond that is associated to the presence of CNT, which was also confirmed by XPS analysis of Figure 6b. The band at 1262 cm-1 is attributed to the asymmetric and symmetric stretching vibration of (C-O-C) groups belonging to 2-substituted furan rings. This band can also be related to the reaction between the CNT-f and the alcohol of furan ring, which increases the presence of C-O-C groups.

Figure 5. FTIR analysis on PFA resins synthesized in the laboratory.

18 18/22

The elemental composition analyses were performed by XPS for the neat and functionalized CNTs. The neat CNT was a reference to evaluate the efficiency of functionalization with carboxylic groups. Figure 7 shows the curve fitting of C1s and O1s core levels[21-23] for neat (Figure 7a1 and 7a2) and functionalized CNT with H2SO4:HNO3 (Figure 7b1 and 7b2), respectively. The C1s spectrum was deconvoluted in six components: C-C (~284.52 eV), C-H (~285.36 eV), C-O (~286.58 eV), C=O (~287.58 eV), O-C=O (~288.58 eV), and plasmon p-p* (~290.82 eV). The oxidative treatment with H2SO4:HNO3 increases the carboxylic group in Polímeros, 28(1), 15-22, 2018

Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite 288.58 eV, due to the insertion of oxygen onto the nanotube surface[20,24]. The curve at the O1s core level was fitted with three components, refering to CO (~535.18 eV), C=O, OH (~532.04 eV), O-2 (iron oxide) (~531.01eV). For oxidative treatments, the proportion of OH and C=O bonds increased, which was mainly due to the presence of carboxylic groups.

Figure 8 shows the curve fitting of the C1s and O1s core levels in the cured PFA and its composite with 2.0 wt% of CNT-f. In Figure 8a1, the binding energies of curve fitting of C1s were identified and related to the bonds of the pure polymer by the numbering indicated in parenthesis in the figure. Four important bonds were identified CH

Figure 6. FTIR spectra with peaks identified for: (a) cured PFA and PFA composites and (b) Expansion of the region until 1600 cm-1 for the band analysis of cured PFA and PFA composites with 0.5, 1.0 and 2.0 wt% of functionalized CNTs.

Figure 7. Curve fitting of C1s and O1s core levels for: (a1 and a2) neat and (b1 and b2) functionalized CNT with H2SO4:HNO3.

Polímeros, 28(1), 15-22, 2018

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Edwards, E. R., Oishi, S. S., & Botelho, E. C.

Figure 8. Curve fitting of C1s and O1s core levels for: (a1 and a2) PFA resin cured with APTS and (b1 and b2) curve fitting of C1s and O1s core levels for functionalized CNT with H2SO4:HNO3.

(~285.46eV), CO (~286.76eV), C=O/COO (~287.90eV) and O-C=O (~289.42eV), with the latter showing a high intensity. In Figure 8a2, the binding energies for the pure material, were identified for the O1s core level with binding energies of CO (~ 533.65 eV) and C=O (~ 532.14 eV).

The results of these analyses were compared to the composite with 2.0 wt% of CNT-f cured under the same conditions.

Figure 8b1 shows the curve fitting of the C1s core levels for the composite with 2.0 wt% of CNT-f while important binding energies were also identified: CC (~ 284.56 eV), CH (285.38 eV), CO (~ 286.00 eV), C=O (~ 287.58 eV) and plasmon p-p* (~ 292.68 eV). There is a large decrease in relative binding intensity of CH (~ 285.38 eV), increasing the CO (~ 286.00 eV) and C=O band (~ 287.58 eV). There is the appearance of the C-C band (~284.56 eV), which refers to the presence of CNTs in the composite. The increase of the CO band (~ 286.00 eV) is probably related to the reaction of the hydroxyl group of carboxylic acid with the hydroxyl group of furan ring. The curve at the O1s core level in Figure 8b2 was fitted with three components, refering to C-O (~532.65 eV), O-C=O (~533.98 eV) and N-O (~531.12 eV). There is an increase in energy intensity of the CO bond, a disappearance 20 20/22

of the C=O bond and an emergence of the O-C=O bond in the composite. The appearance of the N-O bond is also observed, which is related to remaining traces of CNT-f.

Figure 9 shows the influence of CNT in the cure of neat PFA resin and with different percentages of CNT-f. According to our results, a relatively small amount of CNTs in PFA resin matrix is capable of significantly enhancing the viscoelastic properties and modifying the thermal stability, since it was observed that the initial cure temperature (Tgel) of PFA resin, when 0.5, 1.0 and 2.0 wt% of CNT is added, decreases this property at around 2°C, 5°C and 17°C, respectively, when compared with neat PFA resin.

The CNTs bearing active groups can significantly change the surface characteristics of these constituents. These functionalized carbon nanotubes can react in different ways with several materials, such as thermoset and thermoplastic resins, or can act as a catalyst system, thus enhancing the interfacial bond between the matrix while the CNTs can dictate the application of different polymer nanocomposites.

Thus, cured kinetic behavior of furfuryl alcohol resin is highly dependent on the nanocomposite constituents.

Polímeros, 28(1), 15-22, 2018

Analysis of chemical polymerization between functionalized MWCNT and poly(furfuryl alcohol) composite PFA resin has a wide range of applications such as adhesives, porous carbon, polymeric material, etc. Therefore, multifunctional composite materials reinforced with carbon nanotubes may provide a wide range of applications.

From these results, it can be concluded that the process used in this study can contribute with some improvements regarding the manufacture of multifunctional composite materials for industrial applications.

5. Acknowledgements

Figure 9. Viscosity behavior versus temperature for the cured resin with furfuryl resin reinforced with 0.5 wt%, 1.0 wt% and 2.0 wt% of purified NTC.

The reactivity of furfuryl groups probably increases with their nucleophilic nature and, when using an appropriate catalyst as well as an adequate curing temperature, it is possible to lead to a highly crosslinked network. On the other hand, the functionalization of CNTs increases their surface roughness and, when a chemical modification is used, the interaction between the nanotubes and the matrix is usually responsible for the strong adhesion, which is mainly due to the formation of covalent bonds at the interface.

In general, after the functionalization of the nanotubes, the polar groups located on the surface of CNT act as curing agents and accelerate the curing reaction of the thermoset resins. That is, the chemical bonds formed by the carbon nanotubes add the chemical bonds formed by the catalyst (PTSA) accelerate cure.

4. Conclusions We initially proposed reach an understanding of the chemical interaction mechanism of functionalized carbon nanotubes with carboxylic groups and Poly(furfuryl alcohol) (PFA) resin. The proposed mechanism was shown in Figure 1.

This interaction was evident from the data of the FTIR and XPS of the composites. We confirmed this understanding by experimental techniques. Raman showed a functional group added to a wall of carbon nanotubes. The mixture of CNT-f with furfuryl alcohol (FA), in addition to facilitating mixing due to low viscosity, also facilitates the chemical bonds with the functional groups. It was observed that this chemical interaction occurs between CNT-f and furfuryl alcohol, followed by the addition to the PFA. The chemical interaction occurs between hydroxyl group in the polymeric chain and the carboxylic group with the subsequent output of one water molecule. The mixture of CNT-f in the furfuryl alcohol (FA), before being added to the PFA, can be considered a good procedure in order to obtain an adequate chemical interaction between CNT-f and PFA. Moreover, CNT-f acts as curing agent that accelerates the curing reaction of PFA and increases the degree of polymerization. Thus, it is important understand the chemical interaction between the carbon nanotube and the polymer matrix.

Polímeros, 28(1), 15-22, 2018

The authors would like to thank FAPESP, CAPES, CNPq for the financial support received and INPE/DIMARE for the material. The authors declare that they have no conflict of interest.

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5. Xie, X. L., Mai, Y. W., & Zhou, X. P. (2006). Dispersion and alignment of carbon nanotubes in polymer matrix: a review.

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8. Bertarione, S., Bonino, F., Cesano, F., Damin, A., Scarano, D., & Zecchina, A. (2008). Furfuryl alcohol polymerization in H-Y confined spaces: reaction mechanism and structure of carbocationic intermediates. The Journal of Physical Chemistry B, 112(9), 2580-2589. PMid:18266350. http:// dx.doi.org/10.1021/jp073958q.

9. Zhang, S., & Solomon, D. H. (1997). The reaction of furfuryl alcohol resins with hexamethylenetetramine: a 13C and 15N high-resolution solid-state NMR study. Journal of Polymer Science. Part B, Polymer Physics, 35(14), 2233-2243. http:// dx.doi.org/10.1002/(SICI)1099-0488(199710)35:14<2233::AIDPOLB4>3.0.CO;2-X. 10. González, R., Figuero, J. M., & González, H. (2002). Furfuryl alcohol polymerisation by iodine in methylene chloride.

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Edwards, E. R., Oishi, S. S., & Botelho, E. C. 11. Antunes, E. F., Almeida, E. C., Rosa, C. B. F., Medeiros, L. I., Pardini, L. C., Massi, M., & Corat, E. J. (2010). Thermal annealing and electrochemical purification of multi walled carbon nanotubes produced by camphor/ferrocene mixtures.

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13. Edwards, E. R., Antunes, E. F., Botelho, E. C., Baldan, M. R., & Corat, E. J. (2011). Evaluation of residual iron in carbon nanotubes purified by acid treatments. Applied Surface Science, 258(2), 641-648. http://dx.doi.org/10.1016/j.apsusc.2011.07.032.

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19. Barsberg, S., & Thygesen, L. G. (2009). Poly(furfuryl alcohol) formation in neat furfuryl alcohol and in cymene studied by ATR-IR spectroscopy and density functional theory (B3LYP) prediction of vibrational bands. Vibrational Spectroscopy, 49(1), 52-63. http://dx.doi.org/10.1016/j.vibspec.2008.04.013.

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21. Kónya, Z., Vesselényi, I., Kiss, J., Farkas, A., Oszkó, A., & Kiricsi, I. (2004). XPS study of multiwall carbon nanotube synthesis on Ni-, V-, and Ni, V-ZSM-5 catalysts. Applied Catalysis A, General, 260(1), 55-61. http://dx.doi.org/10.1016/j. apcata.2003.10.042.

22. Shulga, Y. M., Tien, T. C., Huang, C. C., Lo, S. C., Muradyan, V. E., Polyakova, N. V., Ling, Y. C., Loutfy, R. O., & Moravsky, A. P. (2007). XPS study of fluorinated carbon multi-walled nanotubes. Journal of Electron Spectroscopy and Related Phenomena, 160(1-3), 22-28. http://dx.doi.org/10.1016/j. elspec.2007.06.002.

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Received: July 13, 2016 Accepted: Dec. 12, 2016

Polímeros, 28(1), 15-22, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.09816

Nitrile rubber and carboxylated nitrile rubber resistance to soybean biodiesel Felipe Nunes Linhares1*, Cléverson Fernandes Senra Gabriel1, Ana Maria Furtado de Sousa1, Marcia Christina Amorim Moreira Leite1 and Cristina Russi Guimarães Furtado1 1 Laboratório de Processamento de Polímeros, Instituto de Química, Universidade do Estado do Rio de Janeiro – UERJ, Rio de Janeiro, RJ, Brazil

*felipe.n.linhares@gmail.com

Abstract Biodiesel has been considered a suitable substitute for petroleum diesel, but their chemical composition differs greatly.

For this reason, biodiesel interacts differently than petroleum diesel with various materials, including rubbers. Therefore, the resistance of some elastomers should be thoroughly evaluated, specifically those which are commonly used in automotive industry. Nitrile rubber (NBR) is widely used to produce vehicular parts that are constantly in contact with fuels. This paper aimed to assess the resistance of carboxylated nitrile rubber (XNBR) with 28% of acrylonitrile content to soybean biodiesel in comparison with non-carboxylated nitrile rubber samples, with high and medium acrylonitrile content (33 and 45%). NBR with medium acrylonitrile content showed little resistance to biodiesel. However, carboxylated nitrile rubber even with low acrylonitrile content had similar performance to NBR with high acrylonitrile content.

Keywords: nitrile rubber, crosslink density, biodiesel, mechanical properties.

1. Introduction Nitrile rubber (NBR) represents a rubber for special purposes and it highly resistant to mineral oils and non‑polar solvents, due to the presence of nitrile groups in its structure.

One of its the main applications is in the automotive industry, in parts that requires constant contact with fuels.

The degradation of nitrile rubber can occur via different ways, including changes in the crosslink network and reactions with free carbon double bonds[1-4]. Carbon black can also accelerate the thermal oxidation process of NBR compounds[1-5].

Some studies[4,6-17] have tested the compatibility of many elastomers to biodiesel, including nitrile rubber (NBR), whose degradation process is often assessed observing changes in the mechanical properties after static and/or dynamic immersion in different types of media at different temperatures.

Biodiesel is a liquid bio-fuel considered to be an environmentally friendly source of energy, and a feasible alternative to petrol-diesel. It is chemically defined as a mixture of mono-alkyl esters obtained from vegetable oils or animal fat.

There are many vegetable sources for biodiesel production, such as soybean oil, palm oil, and rapeseed oil, among others. Some differences in physico-chemical properties are observed depending on the feedstock used for the biodiesel production[18,19].

Petroleum diesel and biodiesel interact differently with various materials, as both are chemically different. For this reason, the properties of biodiesel should be further studied.

To date, biodiesel compatibility with materials that are used widely in diesel engines has not been fully assured.

Polímeros, 28(1), 23-29, 2018

Usually nitrile rubber presents low resistance to biodiesel from different sources. Trakarnpruk and Porntangjitlikit[6], and Dubovský et al.[13] suggested that the deterioration in mechanical properties were due to the plasticization effect of biodiesel. However, the use of a biodiesel/diesel 10% blend (B10) should not be of concern[6].

Haseeb et al.[7,8] inferred that the degradation process occurs due to reactions with the crosslink network, and with the free double bonds in the polymer chains. Linhares et al.[10] concluded that an increase in the acrylonitrile content increases the nitrile rubber resistance to biodiesel. Akhlaghi et al.[4,14] showed that the biodiesel attacks the filler-elastomer interfaces, which affect the mechanical properties; in addition, biodiesel would decrease the crosslink network of elastomer compounds. Akhlaghi et al.[14] also suggested that a prolonged exposure to biodiesel can promote the hydrolisation of nitrile groups of NBR by Zn+2 cations.

Moreover, the chemical differences of biodiesel obtained from different sources can affect the biodiesel solvent power, and, hence, its degradation power[15].

However, most of the authors did not specify the acrylonitrile content in the nitrile rubber samples nor which formulations were used during the tests, impeding a thorough comparison of the results.

Considering that biodiesel is an actual fuel option, and nitrile rubber is largely used for automotive parts production, the need to study the interaction between biodiesel and elastomers is urgent.

This paper aimed to evaluate the resistance of different nitrile rubber samples to soybean biodiesel. The novelty of this paper lies on the assessment of carboxylated nitrile rubber performance after immersion in soybean biodiesel,

23/29 23

O O O O O O O O O O O O O O O O

Linhares, F. N., Gabriel, C. F. S., Sousa, A. M. F., Leite, M. C. A. M., & Furtado, C. R. G. and of the relation of different types of crosslink network with elastomer resistance to soybean biodiesel.

( )

− ln (1 − vr ) + vr + χ vr2   η=  (1),   1   V0  vr3 − vr     r    

2. Materials and Methods 2.1 Compounding

wherein η is the crosslink density; vR is the volume fraction of rubber in equilibrium swollen vulcanizate sample; V0 is the molar volume of the solvent (73.40 mL.mol-1); χ is the interaction parameter between the solvent and the elastomer.

Nitrile rubber samples with different acrylonitrile content (33 and 45%) and carboxylated nitrile rubber (with 28% of acrylonitrile content) were used. The rubber samples were generously given by Nitriflex S/A Indústria e Comércio.

The compositions were prepared in a roll mill, at 50 °C ± 5°C (323K ± 5K), as per ASTM D3187, using the formulation presented in Table 1. The carbon black sample was given

by Cabot do Brasil Indústria e Comércio S.A..

The volume fraction of rubber in equilibrium swollen gel (vR) was calculated according to Equation 2. It is worth mentioning that the filler volume was subtracted of the rubber volume in the calculation.

M1 − f f M1

For identification purposes the compositions prepared were labelled according to the elastomer used in the formulation: NBR33 for the composition prepared with nitrile rubber with 33% of acrylonitrile; NBR45 for the composition with nitrile rubber with 45% of acrylonitrile; and XNBR for the compositions prepared with the carboxylated nitrile rubber with 28% of acrylonitrile content. Further information on the nitrile rubber samples is given in Table 2.

vr =

wherein, M1 is the initial sample mass; fF is the filler fraction volume; ρC is the calculated composition density; M2 is the swollen sample mass; M3 is the deswollen sample mass; ρS is the solvent density (0.79 g.mL-1).

The interaction parameter (χ) for each composition was calculated according to the Equation 3[22].

A small sample of each composition was analysed on a Tech Pro MDPt moving die rheometer (MDR), for one hour, at 160°C (433K) to establish the optimum cure time (t90) of each composition. The compositions were vulcanised in a hydraulic press using their respective t90 to obtain testing specimens for the mechanical tests.

V  χ= ß1 +  0  δ s − δ p  RT 

(

Crosslink density of the samples was calculated by equilibrium swelling with acetone, using the Flory-Rehner equation[20,21] (Equation 1), at room temperature.

2

(3),

The calculated interaction parameter (χ) for NBR33 was 0.3507; for NBR45 was 0.3474; and for XNBR was 0.3640.

The dried compositions density (ρc) was calculated following the Arquimedes’ principle, in which consider the mass of the sample in air, the apperent mass of the sample immersed in the solvent, and the density of the solvent.

The apparent mass of the sample is measured using a proper apparatus, which measures the mass of the sample submerged in the solvent (acetone) held by a thread. The density was, then, calculated according to Equation 4.

Table 1. Formulation of the NBR compositions, as per ASTM D3187, in phra.

Amount in phra 100 3 1 1.5 0.7 40

)

wherein, ß1 is the lattice constant[22] (0.34); R is the universal gas constant; T is the temperature in Kelvin; δS is the solubility parameter of the solvent (9.9 for acetone[23]); δP is the solubility parameter of the polymer (varies for each rubber sample[23]).

2.2 Crosslink density

Component Nitrile rubber Zinc oxide Stearic Acid Sulphur TBBSb Carbon black (SP6630)

ρc (2), M1 − f f M1 M 2 − M 3 + ρc ρs

= ρc

parts per hundred parts of rubber; bN-tert-butyl-2-benzothiazyl sulphenamide. a

M1

( M1 − M 4 )

x ρs (4),

wherein, M4 is the apperent mass of the sample immersed in the solvent.

Table 2. Main properties of the nitrile rubber samples*.

Property Bound acrylonitrile (%) – ASTM D3533 Mooney viscosity (MML1+4 @373K) – ASTM D1646 Ash content (%) – ASTM D5667

Nitrile rubber sample with 33% of acrylonitirle

Nitrile rubber sample with 45% of acrylonitirle

32

46.7

Carboxylated nitrile rubber sample with 28% of acrylonitirle 27.8

45

55

45

0.1

0.1

0.1

*given by the supplier Nitriflex S/A Indústria e Comércio.

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Polímeros, 28(1), 23-29, 2018

Nitrile rubber and carboxylated nitrile rubber resistance to soybean biodiesel 2.3 Immersion tests Pure soybean ethylic biodiesel, kindly donated by CENPES/Petrobras (Brazil), was used for the immersion tests. The biodiesel properties were within the Brazilian regulations, and its main components are ethyl esters derived from mono and poly-unsaturated acids[18,19].

2.4 Change in mass Small rectangular specimens were cut from the vulcanised sheets to assess the change in mass after immersion according to ASTM D471. The specimens were weighed, in air, in a balance with 0.1 mg accuracy. The immersed samples had their surfaces dried with filter paper before they were weighed. The results were the average change in mass from the tested specimens. The immersion was conducted for 22h at 100 °C (373K) in an oven with forced air circulation.

2.5 Mechanical tests Stress-strain tests were performed on a testing machine EMIC, model DL2000, as per ASTM D412, using Die C dumbbell specimens, i.e., 115mm length, and bench mark distance of 25.4 mm. The rate of grip separation was 500 mm/min (±50 mm/min). Tear strength tests were conducted on the same testing machine according to ASTM D624, using Type C test specimens, i.e., an unnicked test piece with a 90° angle on one side, and 102 mm length. The rate of grip separation was also 500 mm/ min (±50 mm/min).

Hardness tests were performed on a durometer Shore A, from Parabor, following ASTM D2240, and the testing

2.6 Scanning electron microscopy After the mechanical tests, the fracture surfaces of the immersed and the non-immersed samples were sputtered with a gold film and analysed by scanning electron microscopy (SEM), using 15 keV electron beam acceleration voltage in a JSM 6510LV microscope from JEOL.

3. Results and Discussions 3.1 Change in mass Change in mass of the compositions after the immersion in the bio-fuel is shown in Figure 1. NBR33, with medium acrylonitrile content (33%), absorbed the fuel in the highest extent, increasing in over than 50% its mass. On the other hand, XNBR, with only 28% of acrylonitrile content, swelled around 30%, and NBR45, as expected, absorbed the oil in much lower extension, increasing in less than 15% of its mass.

Differently from these results, Akhlaghi et al.[14] found an increase in mass between 10 to 15% for nitrile rubber compositions with 34%. The difference in the results can be assigned to the different biodiesel source used (rapeseed in their study and soybean in this study), and also to the lower temperature employed in the cited reference. Nonetheless, the tendency that increasing the acrylonitrile content, decreases the biodiesel uptake was similar in both studies.

The bio-fuel swelling by the NBR33 sample is usually attributed to the “like dissolves like” principle[4] since biodiesel presents some polarity due to its ester nature. The closeness Polímeros, 28(1), 23-29, 2018

Figure 1. Change in mass after 22h of immersion in soybean biodiesel as function of crosslink density of the nitrile rubber compositions.

of polarity between the fluid and the elastomer eases the diffusion of the fuel into the polymer.

Figure 1 also matches the crosslink densities of each composition with the oil mass uptake after 22h. Some authors[7,8] proposed that an increase in acrylonitrile content would increase the crosslink density, which would lessen the bio-fuel swelling. Our results disagreed with these propositions. Crosslink density presented no relation with the compositions’ acrylonitrile content, as NBR45 and NBR33 had similar crosslink density. XNBR can form additional non-sulphur crosslink bonds through the carboxyl groups[24], which explains the highest crosslink density achieved. These crosslinks are formed by the interaction between carboxyl groups and zinc[24].

In addition, the biodiesel swelling was also not related to the crosslink density of the compositions. Carboxylated nitrile rubber (XNBR) absorbed less oil than NBR33, but swelled more oil than NBR45.

We could observe that the crosslink density of the compositions solely does not rule the degree of biodiesel swelling. Based on these results, differences in biodiesel absorption should be assigned to a contribution of both the acrylonitrile content and the type of crosslink.

3.2 Mechanical tests The mechanical test results from the different NBR compositions after the immersion in pure soybean biodiesel were presented as the relative change after the immersion in comparison with those non-immersed ones, and are depicted in Figures 2 and 3.

NBR33 presented very low resistance to soybean biodiesel, given that the losses of the mechanical properties were 66% on average. NBR45, however, experienced less significant losses, 38% on average, after immersion in biodiesel. Previous tests already showed better resistance 25/29 25

Linhares, F. N., Gabriel, C. F. S., Sousa, A. M. F., Leite, M. C. A. M., & Furtado, C. R. G.

Figure 2. (a) Stress at break, and (b) strain at break of nitrile rubber compositions: non-immersed, and after immersion in soybean biodiesel for 22h at 100 °C. Between brackets the percentage of loss of the properties.

Figure 3. (a) Tear strength, and (b) hardness of nitrile rubber compositions: non-immersed, and after immersion in soybean biodiesel for 22h at 100 °C. Between brackets the percentage of loss of the properties.

to biodiesel for samples with higher acrylonitrile content[10], in spite of they had been conducted at different conditions.

Despite having low acrylonitrile content (28%), the carboxylated nitrile rubber composition presented an average loss of 41%, which was close to those observed for high acrylonitrile content composition (NBR45). Moreover, XNBR had a better resistance to biodiesel than medium acrylonitrile content composition (NBR33). This suggests that the resistance of nitrile rubber samples are not merely assigned to the acrylonitrile content of the samples.

This additional type of crosslink improved the rubber resistance to biodiesel, despite the fact that XNBR has the lowest acrylonitrile content among the compositions.

The crosslink networks of the compositions NBR33 and NBR45 were mostly composed by polysulfide crosslinks, which are less resistant to thermal and chemical oxidation.

We could infer that the presence of different types of crosslink network compensates the lower acrylonitrile content.

The losses of stress at break after immersion were matched with the samples’ crosslink densities (Figure 4a) and with the mass change of each composition (Figure 4b).

Comparing the stress at break losses with the change in mass after 22h (Figure 4b), we could highlight that XNBR has a superior resistance to biodiesel, since these samples had similar mechanical performance to NBR45 after immersion in biodiesel, despite of having had a larger oil uptake.

Once again, we could observe that crosslink density solely does not rule rubber resistance to biodiesel (Figure 4a).

NBR33 and NBR45, which have similar crosslink density, presented remarkably different mechanical resistance to biodiesel, which, for these compositions, may be assigned to the difference in the acrylonitrile content. On the other hand, XNBR, with the highest crosslink density, had similar loss to NBR45. As already mentioned, carboxylated samples can form different kinds of crosslink bonds, because of the presence of carboxyl groups.

The mechanical losses observed could be attributed to the reduction of the polymer chains entanglement[6], oxidation of free double bonds, and reduction of polymer-filler interaction[4,7,14,25], which were provoked by the diffusion of the biodiesel into the samples. The detrimental effects of the oil also come from its low oxidative stability, which is due to the high presence of unsaturated components[4,18,26].

The oxidation of biodiesel results in the formation of carboxylic acids as well as water[4], which can detrimentally react with the rubber network.

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Polímeros, 28(1), 23-29, 2018

Nitrile rubber and carboxylated nitrile rubber resistance to soybean biodiesel 3.3 Scanning Electron Microscopy (SEM) SEM analyses were also conducted to give further support to the observations already drawn. The fracture surfaces from all tensile tests specimens’ compositions are shown in Figure 5.

NBR33 showed a highly deteriorated surface after the immersion compared to the non-immersed specimen. Many clusters on the surface of the immersed samples could be observed. The modified surface suggests a strong, yet destructive, affinity between the biodiesel and the elastomer.

Figure 4. Percentage of loss of stress at break after 22h of immersion in soybean biodiesel of the nitrile rubber compositions as function of: (a) crosslink density (a); and (b) mass uptake.

Figure 5. SEM Photomicrographs of fracture surfaces from the nitrile rubber samples. Non-immersed samples, and after immersion in soybean biodiesel for 22h at 100 °C. Polímeros, 28(1), 23-29, 2018

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Linhares, F. N., Gabriel, C. F. S., Sousa, A. M. F., Leite, M. C. A. M., & Furtado, C. R. G. On the other hand, the surface of NBR45 sample was not much attacked after the immersion, as no modification was observed, which suggests weak affinity between the fuel and the composition with high acrylonitrile content.

This suggestion is corroborated by the low oil uptake by that composition. This behaviour is beneficial considering the use of this type of nitrile rubber in some applications.

The photomicrographs from XNBR fracture surface only presented a few small clusters formed, indicating a moderate chemical interaction between the elastomer and the biodiesel. The different nature of the crosslink bonds might have contributed to lower detrimental interactions, despite the lower acrylonitrile content.

Furthermore, the SEM photomicrographs corroborates the results observed in Figure 1. It was observed that the compositions which absorbed more biodiesel presented a more modified fracture surface after immersion.

4. Conclusions Based on the results from the mechanical tests and the SEM analyses, we could conclude the compositions NBR45 and XNBR presented similar mechanical performace after immersion in soybean biodiesel. Moreover, despite having lower acrylonitrile content (28%), the carboxylated nitrile rubber exhibited a better performance after immersion in soybean biodiesel compared to the medium-acrylonitirle‑content composition (NBR33). Furthermore, other conclusions could also be drawn from our results: 1) Increasing the acrylonitrile content of the elastomer improves the resistance of nitrile rubber samples to biodiesel; 2) Different crosslink systems also enhance the resistance to biodiesel, despite the acrylonitrile content; 3) The stress and strain losses were not directly affected by the amount of biodiesel absorbed by the compositions.

5. Acknowledgements The authors acknowledge Nitriflex S/A Indústria e Comércio and Cabot do Brasil Indústria e Comércio S.A. for material supply; Centro de Pesquisa e Desenvolvimento Leopoldo Américo Miguez de Mello (CENPES/PETROBRAS) for the biodiesel supply; Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for the financial support; Richard T. Herbert for English revision.

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2. Xiong, Y., Chen, G., Guo, S., & Li, G. (2013). Lifetime prediction of NBR composite sheet in aviation kerosene by using nonlinear curve fitting of ATR-FTIR spectra. Journal 28 28/29

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5. Mostafa, A., Abouel-Kasem, A., Bayoumi, M. R., & El-Sebaie, M. G. (2009). The influence of CB loading on thermal aging resistance of SBR and NBR rubber compounds under different aging temperature. Materials & Design, 30(3), 791-795. http:// dx.doi.org/10.1016/j.matdes.2008.05.065.

6. Trakarnpruk, W., & Porntangjitlikit, S. (2008). Palm oil biodiesel synthesized with potassium loaded calcined hydrotalcite and effect of biodiesel blend on elastomer properties. Renewable Energy, 33(7), 1558-1563. http://dx.doi.org/10.1016/j. renene.2007.08.003.

7. Haseeb, A. S. M. A., Masjuki, H. H., Siang, C. T., & Fazal, M. A. (2010). Compatibility of elastomers in palm biodiesel.

Renewable Energy, 35(10), 2356-2361. http://dx.doi.org/10.1016/j. renene.2010.03.011.

8. Haseeb, A. S. M. A., Jun, T. S., Fazal, M. A., & Masjuki, H. H. (2011). Degradation of physical properties of different elastomers upon exposure to palm biodiesel. Energy, 36(3), 1814-1819. http://dx.doi.org/10.1016/j.energy.2010.12.023.

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Mechanical characteristics of swollen elastomers under cyclic loading. Materials & Design, 44(x), 566-572. http://dx.doi. org/10.1016/j.matdes.2012.08.027.

10. Linhares, F. N., Corrêa, H. L., Khalil, C. N., Leite, M. C. A. M., & Furtado, C. R. G. (2013). Study of the compatibility of nitrile rubber with Brazilian biodiesel. Energy, 49(1), 102-106. http://dx.doi.org/10.1016/j.energy.2012.10.040.

11. Chai, A. B., Andriyana, A., Verron, E., Johan, M. R., & Haseeb, A. S. M. A. (2011). Development of a compression test device for investigating interaction between diffusion of biodiesel and large deformation in rubber. Polymer Testing, 30(8), 867-875. http://dx.doi.org/10.1016/j.polymertesting.2011.08.009.

12. Andriyana, A., Chai, A. B., Verron, E., & Johan, M. R. (2012).

Interaction between diffusion of palm biodiesel and large strain in rubber: effect on stress-softening during cyclic loading.

Mechanics Research Communications, 43, 80-86. http://dx.doi. org/10.1016/j.mechrescom.2012.03.004.

13. Dubovský, M., Božek, M., & Olšovský, M. (2015). Degradation of aviation sealing materials in rapeseed biodiesel. Journal of Applied Polymer Science, 132(28), 42254. http://dx.doi. org/10.1002/app.42254.

14. Akhlaghi, S., Pourrahimi, A. M., Hedenqvist, M. S., Sjöstedt, C., Bellander, M., & Gedde, U. W. (2016). Degradation of carbon-black-filled acrylonitrile butadiene rubber in alternative fuels: Transesterified and hydrotreated vegetable oils. Polymer Degradation & Stability, 123, 69-79. http://dx.doi.org/10.1016/j. polymdegradstab.2015.11.019.

15. Zhu, L., Cheung, C. S., Zhang, W. G., & Huang, Z. (2015).

Compatibility of different biodiesel composition with acrylonitrile butadiene rubber (NBR). Fuel, 158, 288-292. http://dx.doi. org/10.1016/j.fuel.2015.05.054.

16. Coronado, M., Montero, G., Valdez, B., Stoytcheva, M., Eliezer, A., García, C., Campbell, H., & Pérez, A. (2014). Degradation of nitrile rubber fuel hose by biodiesel use. Energy, 68, 364369. http://dx.doi.org/10.1016/j.energy.2014.02.087.

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Nitrile rubber and carboxylated nitrile rubber resistance to soybean biodiesel 17. Akhlaghi, S., Gedde, U. W., Hedenqvist, M. S., Braña, M. T. C., & Bellander, M. (2015). Deterioration of automotive rubbers in liquid biofuels: a review. Renewable & Sustainable Energy Reviews, 43, 1238-1248. http://dx.doi.org/10.1016/j. rser.2014.11.096.

18. Giakoumis, E. G. (2013). A statistical investigation of biodiesel physical and chemical properties, and their correlation with the degree of unsaturation. Renewable Energy, 50, 858-878. http://dx.doi.org/10.1016/j.renene.2012.07.040.

19. Singh, S. P., & Singh, D. (2010). Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: a review. Renewable & Sustainable Energy Reviews, 14(1), 200-216. http://dx.doi. org/10.1016/j.rser.2009.07.017.

20. Oliveira, I. T. D., Pacheco, E. B. A. V., Visconte, L. L. Y., Oliveira, M. R. L., & Rubinger, M. M. M. (2010). Efeito de um novo acelerador de vulcanização nas propriedades reométricas de composições de borracha nitrílica com diferentes teores de AN. Polímeros: Ciência e Tecnologia, 20(Especial), 366-370. http://dx.doi.org/10.1590/S0104-14282010005000059.

21. Flory, P. J. (1953). Principles of polymer chemistry. Ithaca: Cornell University.

22. Barlkanl, M., & Hepburn, C. (1992). Determination of crosslink density by swelling in the castable polyurethane elastomer

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based on 1/4 – cyclohexane diisocyanate and para-phenylene diisocyante. Iranian Journal of Polymer Science & Technology, 1(1), 1-5.

23. Forrest, M. J. (2001). Rubber analysis – polymers, compounds and products. Wolverhampton: Rapra Technology Ltd. 24. Ibarra, L., Rodríguez, A., & Mora-Barrantes, I. (2008).

Crosslinking of unfilled carboxylated nitrile rubber with different systems: influence on properties. Journal of Applied Polymer Science, 108(4), 2197-2205. http://dx.doi.org/10.1002/ app.27893.

25. Haseeb, A. S. M. A., Fazal, M. A., Jahirul, M. I., & Masjuki, H. H. (2011). Compatibility of automotive materials in biodiesel: a review. Fuel, 90(3), 922-931. http://dx.doi.org/10.1016/j. fuel.2010.10.042.

26. Santos, E. M., Piovesan, N. D., Barros, E. G., & Moreira, M. A. (2013). Low linolenic soybeans for biodiesel: characteristics, performance and advantages. Fuel, 104, 861-864. http://dx.doi. org/10.1016/j.fuel.2012.06.014.

Received: July 20, 2016 Revised: Nov. 24, 2016 Accepted: Jan. 17, 2017

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ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.11516

O O O O O O O O O O O O O O O O

Microstructure and thermal and functional properties of biodegradable films produced using zein Crislene Barbosa de Almeida1*, Elisângela Corradini2, Lucimara Aparecida Forato3, Raul Fujihara1 and José Francisco Lopes Filho1 Departamento de Engenharia e Tecnologia de Alimentos, Universidade Estadual Paulista – UNESP, São José do Rio Preto, SP, Brazil 2 Universidade Tecnológica Federal do Paraná – UTFPR, Londrina, PR, Brazil 3 Empresa Brasileira de Pesquisa Agropecuária – EMBRAPA, São Carlos, SP, Brazil

1

*cris_zootecnista@hotmail.com

Abstract Research is being conducted in an attempt to produce biodegradable packaging to replace plastic products, thereby reducing solid waste disposal. In this work, zein films were produced from vegetable oils (macadamia, olive and buriti) and from pure oleic acid. The surface of zein-based films made using oleic acid has a good lipid distribution. The high content of oleic acid produced a film with the greatest elongation at break (8.08 ± 2.71%) due to the greater homogeneity of the protein matrix. The different oils did not affect the glass transition temperature (Tg). Tg curves of films with fatty acids showed a reduction in mass at between 50 and 120 °C due to water evaporation. At 120 °C the weight loss was 3-5% and above this temperature further weight loss was observed with the highest loss being seen in the film made using pure oleic acid. In conclusion, although biodegradable films were produced using the four different oils, the film made from pure oleic acid has the best characteristics.

Keywords: biodegradable films, biomaterial, zein.

1. Introduction Around the world, there is great concern about producing renewable materials from biomass. Due to environmental issues and sustainability, biomaterials produced from organic residues are the subject of several studies.

Among the many available raw materials suitable for the production of biodegradable products, starch and proteins are being used to create polymeric matrixes due to their good polymerization properties and because they are totally biodegradable. Both materials, similar to conventional synthetic polymers, are processed with the addition of plasticizers.

The biopolymer zein comprises 50% of the proteins in mature corn kernels[1]; it has hydrophobic characteristics due to its high content of apolar amino acids, in addition to its high degree of polymerization. Zein offers advantages as a raw material in the production of biomaterials, coatings and plastic applications as it is biodegradable and renewable[2-4].

It has been used to develop functional biodegradable packaging[5], packages with antimicrobial agents[6-9], packaging for periodontal biomaterials and substrates for cell culture[10].

Studies with zein have been carried out in respect to the regeneration of osseous tissues[11], with nanoparticles used to improve the mechanical properties of films[12,13] and edible film to increase the shelf life of pears[14] and macadamia[15].

The preparation of a film solution requires highmolecular-weight agents called matrix formers, solvents, plasticizers and, when necessary, a pH adjuster[16]. These components are used in different combinations to give films different characteristics.

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Plasticizers are low-molecular-weight organic compounds used to reduce the intermolecular bonding forces, thereby giving high molecular mobility and flexibility to the film[17].

However, an excess of plasticizers results in a reduction of the mechanical properties of the film[18]. Glycerol is most frequently used even though it has hydrophilic properties[19,20].

The greater the amount of glycerol added to produce biopolymer-based films, the lower the stress rupture strength and the Young’s modulus and so the elongation at break is higher. Many formulations include fatty acids, such as oleic, linoleic, stearic and palmitic fatty acids[21].

Some edible vegetable oils have large amounts of oleic acid and so potentially, they can be used as plasticizers in the production of zein films. Of the oils containing fatty acids, buriti (Mauritia flexuosa), macadamia and olive oil are of great interest as the fatty acid levels are greater than 60%.

Scanning electron microscopy (SEM) is the method most commonly used to evaluate the microstructure of biodegradable films. With this technique, it is possible to see whether the structure of the resulting biomaterial is uniform or if the components do not mix. Another important method to complement SEM in the analysis of the homogeneity of the matrix of films is optical microscopy (OM) which allows the characterization of the components by assessing their color and shape.

Thermal and mechanical analyses are important to determine the conditions under which the film can be used and the types of food that can be packaged. The glass transition temperature (Tg) is of much interest to food

Polímeros, 28(1), 30-37, 2018

Microstructure and thermal and functional properties of biodegradable films produced using zein scientists because it helps to explain the chemical and physical behavior of food systems[22]. The Tg of films is important as this characteristic limits the use of the material under extreme conditions, such as at freezing temperatures and during sterilization. The value of the Tg is primarily governed by the chemical composition particularly the presence of plasticizers, and secondarily by structural characteristics such as chain branching, crosslinking and crystallinity[23].

The Tg also provides information on the compatibility of the matrix constituents in a film, especially in the cases of blends/composites[24,25]. Thus, knowledge of the Tg of biodegradable films, specifically edible films, helps in the choice of the best storage conditions.

Good mechanical properties are also required and therefore, the elongation percentage and the tensile strength of the film need to be studied. The aim of this study was to produce biodegradable films of zein using pure oleic acid and edible vegetable oils (macadamia, buriti and olive oil) and to determine their microstructures and functional properties.

2. Materials and Methods 2.1 Biodegradable films Zein (Freeman Industries, Inc. NY, USA) was used at a ratio of 20% (w/v) in 75% ethanol solution. Other components were used in the following proportions in respect to 100g of zein: 70g edible vegetable oil (macadamia, olive or buriti) purchased at local shops (Vital Atman, La Violeteira and Rio Essências, respectively) or 70g of oleic acid (VETEC, Brazil) and 30g of glycerol (Merck, Brazil) as plasticizers and 5g of Emustab® emulsifier (Duas Rodas Industrial Ltda., Brazil) to facilitate emulsification.

After combining the components, the filmogenic solution was heated to 62 °C while stirring at 250 rpm to be subsequently cast on rectangular acrylic plates and maintained at 25 °C for 24 hours to dry. The films were peeled off the acrylic plates and stored inside a desiccator at 58% relative humidity until analyses.

2.2 Composition analysis of the fatty acids of vegetable oils The fatty acid composition of oils was investigated at the Instituto de Tecnologia de Alimentos (ITAL), Campinas[26-29].

2.3 Scanning electron microscopy SEM was performed on 12-mm round samples of film fixed under stubs using double-sided adhesive tape with conductive copper and covered with 35 nm of gold (EMITEC K550, UK). Samples were examined in duplicate by electronic microscopy (LEO 435 VP, UK) at 15 kV in a climate room.

2.4 Optical microscopy Optical Microscopy (OM) was used to identify the compounds of the films. Duplicate samples were stained with Xylidine Ponceau (pH = 2.5) directly and dehydrated at 37 °C for 24 hours (Odontobras ECB 1.2 Digital, Brazil).

The samples were analyzed at room temperature using an Polímeros, 28(1), 30-37, 2018

optical microscope (Olympus BX 60, USA) with an image capture system (Olympus DP 71, USA). Different points in the sample were analyzed at 10× magnification.

2.5 Analysis of differential scanning calorimetry Measurements were made using a differential scanning calorimeter (TA Instruments - TA Q100). Approximately 6-mg samples were subjected to pre-heating from 25 °C to 120 °C to eliminate the thermal history. They were then reheated to 120 °C or 200 °C at a rate of 10 °C/minute under a nitrogen flow of 50 mL/minute. The Tg and melting temperature (Tm) were obtained from the minimum of the first derivative and minimum peak on the differential scanning calorimetry (DSC) curve, respectively.

2.6 Thermogravimetric analysis The thermal stability of the materials was studied using a thermogravimetric analyzer (TGA - TA Instruments, Model Q500). All tests used a mass of approximately 7.0 mg under a nitrogen flow of 50 mL/minute and heating rate of 10 °C/minute within the temperature range of 25 to 900 °C.

2.7 Mechanical properties Tensile strength tests were performed with a Universal‑Instron device (Model 5569, Instron Engineering Corp., Canton, MA) following the standard testing methods ASTM D882‑91[30].

Tensile strength at break (σr), elongation at break (εr) and the Young’s modulus (E) were determined.

3. Results and Discussion 3.1 Appearance and thickness of the films After drying, the films were peeled off the rectangular acrylic plates and visual and tactile analyses were carried out in order to analyze only homogeneous samples in respect to thickness and without cracking. The color and thickness of the material should be uniform, there should be no brittle areas, and the material should be easy to handle. Films that did not have these characteristics were discarded.

The thickness was obtained by the arithmetic mean of six random points in different segments of the film using a digital micrometer (Digimess) at a resolution of 0.001 mm.

All films had uniform thicknesses from 0.19-0.20 ± 0.02 mm.

3.2 Characterization of edible vegetable oils The content of fatty acids of edible oils and the oleic acid used in the formulations are shown in Table 1.

Table 1. Fatty acid composition of plasticizing oils used in the formulation of zein films.

Plasticizers Oleic acid Buriti oil Macadamia oil Olive oil

Oleic (%) 73.2 35.1 61.0 64.7

Linoleic (%)

Palmitic (%)

Palmitoleic (%)

4.0 53.6 1.7 17.1

4.1 5.5 7.9 11.3

3.7 0.1 16.8 0.7

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Almeida, C. B., Corradini, E., Forato, L. A., Fujihara, R., & Lopes Filho, J. F. Fatty acid composition of edible oils and oleic acid are in accordance with the literature regarding the concentration of oleic acid (above 60%) except for buriti oil. Buriti oil has less than 60% of oleic acid (35.1%), but has a concentration of 53.6% of linoleic acid. Both acids produce materials with good flexibility and functional properties[31].

3.3 Scanning electron microscopy Micrographs (Figure 1) show that the films made with macadamia and buriti oil had similar structures with the homogeneous presence of rounded components that look like pores on the surface of the biomaterials. The lipid volume fraction in the dry film and the size of lipid aggregates are the main factors involved in the optical heterogeneity of the film matrix[32]. Films produced by the casting method show different morphological shapes due to drying with the side in contact with air presenting an irregular and opaque appearance and black globular deposits[33].

The presence of globular deposits or pores was verified by the presence of rounded structures, showing that a continuous filmogenic matrix did not form. This observation was also reported in zein films[12,19,34-36], chitosan film[37] and pectin[38].

The films produced with oleic acid (Figure 1c) and olive oil (Figure 1d) showed a smaller number of rounded forms and a significant reduction in the size of the fat globules thus demonstrating that a more homogenous matrix had been created.

3.4 Optical microscopy Optical microscopy was used to complement the SEM analysis of the homogeneity of the matrix of films in respect to the pore-like rounded forms similar to globular deposits.

The Xylidine Ponceau technique provides two types of staining; red represents protein (zein) and white represents lipid globules.

Images of each sample are shown in Figures 2 and 3, with the scales of the micrographs being 4× (10 μm) and 10× (500 μm), respectively.

The micrographs show that zein film produced from oleic acid has greater homogeneity (Figure 3c, d) supporting the results of the SEM analysis. Moreover, the film made using macadamia oil (Figure 2c, d) was more homogeneous than the films of buriti (Figure 2a, b) and olive oil (Figure 3a, b).

The arrangements of the fat globules in the films made with buriti and olive oil are more heterogeneous and larger, suggesting that a higher oleic acid content produces a more homogeneous material.

In addition, there is much streaking suggesting aligned fibrillar proteins which demonstrates that the incorporation of the plasticizer was not uniform in the matrix[34,39].

The homogeneity of the material seems to be correlated with the quantity (%) of oleic acid in the oils because pure oleic acid produced the most uniform film with the best structural and functional characteristics and buriti oil the

Figure 1. SEM micrographs of surfaces of: (a) zein- buriti oil; (b) zein-macadamia oil; (c) zein-oleic acid and (d) zein-olive oil. The increase indicative bar corresponds to 10 µm.

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Polímeros, 28(1), 30-37, 2018

Microstructure and thermal and functional properties of biodegradable films produced using zein

Figure 2. Image Optical Microscopy with Xylidine Ponceau for films: (a, b) zein-buriti oil and (c, d) zein-macadamia oil. The increase indicative bar corresponds 4× (10 µm) and 10× (500 μm).

Figure 3. Image Optical Microscopy with Xylidine Ponceau for films: (a, b) zein-olive oil and (c, d) zein-oleic acid. The increase indicative bar corresponds 4× (10 µm) and 10× (500 μm).

Polímeros, 28(1), 30-37, 2018

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Almeida, C. B., Corradini, E., Forato, L. A., Fujihara, R., & Lopes Filho, J. F. least uniform; Buriti oil has the lowest content of oleic acid (Table 1).

The optical microscopy analysis showed that the artifacts identified by SEM and believed to be pores are in fact fat globules in the film matrix. Almeida et al.[36] also observed this in films produced with xanthan gum and zein.

3.5 Differential scanning calorimetry Thermograms of the films show exothermic and endothermic peaks that characterize transitions or reactions that occurred during analysis, such as the Tg, Tm and crystallization (Tc), among others. Figure 4 shows the DSC curves with the Tm and Tc and Figure 5 shows the expanded region of the DSC curves between 25 °C and 100 °C of the materials studied.

The small peaks in the direction of exothermic heat flow occurring between -55 °C and -35 °C, clearly seen in the films produced with buriti and macadamia oil, are attributed to the crystallization of the residual water (Tc) in the matrices[40]. Moreover, the peaks observed for all materials in the direction of endothermic heat flow, between -30 °C and 3 °C, are explained by the Tm of the oils.

The external factor that changes the Tg and Tm of a film is the presence of plasticizers in the liquid form[41].

By analyzing the composition of the fatty acids, it was found

that buriti oil contained a higher concentration of linoleic acid (53.6%) than oleic acid (35.1%). The Tm of oleic acid is -2.2 °C, while buriti oil has a lower Tm (-29.8 °C). This is due to the lower content of oleic acid present in buriti oil; the film made from this oil has a different chemical structure.

These results confirm observations in literature who reported that oleic acid, which is the major component of the oils studied, presents a solid-solid phase transition of the order-disorder type (γ→α) at -2.2 °C[42].

The Tg of pure zein powder is in the range of 150 to 180 °C; this decreases to 50 °C to 80 °C when fatty acids or polyols are added[43,44]. In this study, the Tg of the zein films were in the range of 47 °C to 50 °C (Figure 5). The lowest value (47.6 °C) was for the zein film made with oleic acid and the highest temperatures were obtained for the films produced from macadamia and olive oil (49.6 °C and 49.5 °C, respectively).

Although there was no significant difference between the temperatures of the films, this result may be due to the purity and content of the oleic acid in the plasticizers as according to Lucas et al.[45], larger amounts of plasticizer will reduce the Tg.

3.6 Thermogravimetric analysis Thermal stabilities of zein in its native form (powder), zein film without plasticizer and plasticized films were determined by thermogravimetry (TG). The TG curves and the first derivative or derivative thermogravimetry (DTG) for zein powder and the zein film prepared without plasticizers are shown in Figures 6a and 6b, respectively.

Figure 4. DSC curves of four zein biomaterials in temperature range of -90 to 90 °C.

The thermal behaviors of zein powder and zein film are quite similar. Initially, weight loss occurs in the temperature range of 25 °C to 120 °C due to the evaporation of water.

Between 120 °C and 200 °C, there is a slight weight loss probably because of the evaporation of fatty acids. The main thermal degradation for zein powder and film occurs in the range of 270 °C to 415 °C. These results are in accordance with the literature[43,46]. There is also a slight shift to higher temperatures at the peak of the decomposition curve (DTG) obtained for the zein film compared to the peak of zein powder decomposition, which may be due to structural differences between zein powder and zein film.

Figure 5. DSC curves showing Tg of zein films.

Major thermal degradation of the films occurs in the range of 250 °C to 405 °C. For all materials, the slight weight loss seen in the temperature range from 110 °C to 200 °C is probably due to the evaporation of fatty acids or glycerol because glycerol plasticizer, analyzed in isolation, has a decomposition temperature of around 213 °C[48]. Note that the weight loss started at a lower temperature in the film made with pure oleic acid. These results are similar to those found in the literature for zein powder[43,46,47]. Small changes in the peaks at higher temperatures were also observed. This is

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Figures 7a and 7b show the TG and DTG curves, respectively, for the plasticized zein films made with different vegetable oils. TG curves for all films showed a weight loss at 50 °C to 120 °C due to water evaporation. The materials also exhibited a weight loss of 3-5% at 120 °C; these values are similar to those obtained by Corradini[47]. Successive weight losses are noted above 120 °C for all materials.

Polímeros, 28(1), 30-37, 2018

Microstructure and thermal and functional properties of biodegradable films produced using zein

Figure 6. (a) TG curves for zein powder and zein film without plasticizer; (b) Curves of the first derivative (DTG) of Figure 7a.

Figure 7. (a) TG curves; (b) DTG curve for zein films with plasticizers.

related to the decomposition curve obtained for zein films produced using buriti, macadamia and olive oil in relation to the peak of the control film decomposition. This result may be due to structural differences between oleic acid and other fatty acid components of the oils.

3.7 Mechanical properties The mechanical properties of the films were affected by the type of plasticizer added. Table 2 shows the values found for tensile strength (σr), elongation at break (εr) and Young’s modulus (E).

Films made with oleic acid had the highest percentage of elongation (8.08% ± 2.71) which is related to the elasticity of the materials. Similar results were reported[49]. The films made with macadamia oil had the lowest percentage of elongation at break (0.93 ± 0.24%) due to the lower homogeneity of the protein matrix. The percent of elongation decreases when fatty acids are not incorporated into the matrix[50,51].

This tendency is explained by the fact that lipids are unable to form a cohesive and continuous matrix.

The addition of lipids also affects the tensile strength and Young’s modulus of the films; these values are the lowest when the concentration of lipids in the matrix is Polímeros, 28(1), 30-37, 2018

Table 2. Tensile Strength (σr), Elongation at Break (εr) and Young’s modulus (E) for the zein films.

Film zein-oleic acid zein-buriti oil zein-macadamia oil zein-olive oil

Tensile strength (σr)

Elongation at break (εr)

Young’s modulus (E)

(MPa) 0.64 ± 0.27 1.66 ± 0.29 1.30 ± 0.45

(%) 8.08 ± 2.71 1.19 ± 0.38 0.93 ± 0.24

(MPa) 48.6 ± 16.8 278.28 ± 17.67 278.86 ± 28.06

1.02 ± 0.26

1.20 ± 0.46

202.59 ± 13.71

optimized[50,52,53]. Thus, the tensile results indicate that the control film (pure oleic acid) was the most homogeneous as the cohesion between the components of the matrix was the highest.

4. Conclusions It was possible to produce biomaterials of zein using edible oils as plasticizers. Although all formulations formed biodegradable films, the film made from pure oleic acid had the best characteristics. Other techniques should be tested, such as ultrasonic frequency during the preparation 35/37 35

Almeida, C. B., Corradini, E., Forato, L. A., Fujihara, R., & Lopes Filho, J. F. of the filmogenic solution, to improve the formation of the matrix of the films and, consequently, improve the thermal and mechanical properties of the films.

5. Acknowledgements The authors express their sincere thanks to the CAPES – “Brazilian Federal Agency for Support and Evaluation of Graduate Education within the Ministry of Education of Brazil” for the postgraduate fellowship and EMBRAPA – “Brazilian Agricultural Research Corporation” (São Carlos/Brazil) for analysis support.

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Received: Nov. 30, 2016 Accepted: Apr. 02, 2017

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ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.06816

O O O O O O O O O O O O O O O O

FSSC 22000 Packaging Implementation: a Plastics Industry Research Vanessa Cantanhede1*, Karen Signori Pereira2 and Daniel Weingart Barreto3 Chemistry School, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil Biochemical Engineering, Chemistry School, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil 3 Organic Processes, Chemistry School, Universidade Federal do Rio de Janeiro – UFRJ, Rio de Janeiro, RJ, Brazil

1 2

*vanessacantanhede@gmail.com

Abstract This paper presents the outcomes of an exploratory research carried out in companies, which are located in Brazil.

They are FSSC-22000-certified food plastic packaging manufacturers. In order to identify the key aspects of the implementation process and certification, a questionnaire was developed and sent to twenty certified organizations.

Out of them, eleven of which participating companies responded in a collaborative way. Based on the data obtained, improving competitiveness and customer retention were the reasons, which led the companies to seek the certification.

However, the greatest difficulties were related to personnel, which presented technical and behavioral issues. In addition, it was noted that an overall satisfaction, derived from after-certification benefits, has been arisen in the companies.

For instance, enhanced employee awareness, improved company’s image and winning new customers, significantly contributing to their competitiveness, are some of the benefits found in this process.

Keywords: food safety, FSSC 22000, packaging, plastic.

1. Introduction Since the 1990s, a significant change has taken place in Brazilian industries mainly due to trade liberalization.

In addition, the pursuit of competitiveness has become their focus. As a result of both internal (defect reduction) and external motivators (increased customer satisfaction), quality programs have been valued and implemented by organizations as a response to new economic conditions[1].

Therefore, companies have adopted quality assurance systems based on international standards, such as ISO 9001, in this particular case[2]. It is extremely important, due to the fact that international standards and norms facilitate trade among countries, help ensure technical compatibility and feasibility of marketed products. Besides, it also generates product reliability.

Simultaneously, because of trade liberalization, a relevant growth in food imports took place in Brazil. From 1992 to 1995, the import of processed food grew by 409%[3].

Due to the wide range of products and services, marketed worldwide, economic globalization and industrialization play an important role. Currently, the scenario is highly competitive and Brazil is ranked among the world’s largest food exporters. In addition, in agribusiness, including the export of coffee beans, soybeans and raw material, Brazil holds the 5th place[4]. Food and beverage industries’ production represent 9.5% of the Brazilian Gross Domestic Product (GDP), in addition to creating an increasing number of jobs, generating a greater balance of trade, if compared to the other economy sectors[5].

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However, it is very important to note that, in addition to market expansion, trade liberalization and the progressive industrialization, there were several changes in the food industry, both in production and in marketing. One of the main changes was the increased social concern on food safety, which is already considered a global public health issue by the World Health Organization (WHO).

Food Safety is related to the concept that indicates the food will not cause any harm to the consumer’s health when prepared and/or eaten according to its intended use[6].

Thus, increasingly competitive strategies are developed by the agri-food industry groups, in order to win consumer confidence in quality, provenance and food safety[7], ensuring that consumer health is not affected.

Among the different packaging markets, the plastic packaging segment stands out. Between 2007 and 2011, its value (US$) grew by 7.9% per year, highlighting the food and beverage industry, as the largest consumer[8]. It also had the highest share in production value, corresponding to 39.07% of the total in 2014[9]. Thus, the high consumption of plastic packaging for the food industry and the expansion of this sector were the main reasons to choose the plastics segment for this research paper.

Packages have a prominent role in the food supply chain and are essential to ensure product safety. The growth of this sector follows the food industry development and, according to ABRE (Brazilian Packaging Association), the packaging sector currently generates R$ 47 billion (Brazilian currency) and more than 200,000 direct and formal jobs[10].

Polímeros, 28(1), 38-43, 2018

FSSC 22000 Packaging Implementation: a Plastics Industry Research The food safety subject in the packaging industry has been getting more and more relevance in recent years. It can be evidenced by the recent publication of an international standard. The FSSC 22000 contains a complete certification Scheme for Food Safety Management Systems based on existing standards for certification (ISO 22000 and technical specifications for sector PRPs). It is considered complete and the latest certification scheme for food safety systems[11].

The FSSC 22000 scheme was given full recognition in 2010 by the Global Food Safety Initiative (GFSI). It is an industry-driven initiative providing guidance on food safety management systems, wich are necessary for safety throughout the supply chain. This work is accomplished through collaboration between the world’s leading food safety experts from retail, manufacturing and food service companies, as well as international organizations, governments, academia and service providers to the global food industry. GFSI´s vision is to provide safe food for consumers everywhere[11].

In 2011, a specific version for the food packaging segment was published (FSSC 22000 Packaging), and brought a new market perspective, emphasizing the need to ensure that products are free from contaminants throughout the food chain.

Already, 10.000 more organizations over 140 countries achieved FSSC 22000 certification. In Brazil, 291 certified companies, and among these, 66 are food-packaging industries. These data were verified in July 2015 during the present study and it confirms the growth and adherence of companies to the FSSC 22000 certification[12].

This paper mainly aims to evaluate the FSSC 22000 implementation process in plastic packaging companies for the food industry and certification impacts regarding competitiveness of those companies in the packaging market.

Therefore, a survey was conducted in certified organizations established in Brazil, which identified the profile of those companies, the drivers to obtain certification, the main facilitators and challenges faced during the implementation of this standard, and the effects achieved through the implementation of FSSC 22000.

2. Materials and Methods 2.1 Questionnaire elaboration As from bibliographic research to scientific articles published in the last five years, addressing issues concerning the benefits and difficulties in management systems and specifically in food safety systems, a questionnaire template was designed for FSSC 22000 standard certified packaging industries.

The questions were developed so as not to have direct intervention nor influence of the researcher on researches[13].

By the exploratory approach of the research, most questions were created in such a way in order not to induce responses, thus it promoted room for spontaneous responses by informants.

The questionnaire was structured as follows. The first part features the participating companies, the number of employees, year of foundation, company size, the market where it operates and location. The second part characterizes the standard implementation process and its duration, for example Polímeros, 28(1), 38-43, 2018

“what were the reasons to adopt the standard?”; “In which of the options, the company had higher expenses / financial investments?”; “What were the difficulties faced”; “it were necessary to hire an external advice firm?. The third part, which aims to identify the benefits and the satisfaction level, obtained after the certification.

The finalized questionnaire was validated by professionals from this universe, as a pilot test, to be studied, before it was effectively sent to the companies, as suggested in literature[14]. As a result of this validation, changes were made in a few questions.

2.2 Sampling As from the evaluation certified organizations’ database, available on the certificates directory of Foundation for Food Safety Certification website[12], only plastics segment companies, which are located in the country, were selected.

In total, 20 plastics manufacturers had the FSSC 22000 Packaging certification when the consultation was carried out in August 2015. For this survey, in the analysis made by sectors within the plastics industry, company groups were established according to the type of product they manufacture. And it is represented in Table 1.

2.3. Conducting the Questionnaire Survey The questionnaire was electronically sent via e-mail to those who were responsible for the Quality department at the selected companies. 55% of the questionnaires were effectively responded. It is important to mention that, before sending them, each company was contacted by telephone, in order to present and explain the survey. All the process, from the first contact with the organizations to the final data compilation, took place between August 2015 and December 2015. Due to the difficulty with colleting the organizations’ responses, this process was long.

The information asked in the questionnaires was individually evaluated. Besides the data collected were tabulated in order to systematize the all pieces of information. Thus, they were grouped up so that they could be statistically analyzed.

3. Results and Discussions 3.1 Characterization of responding organizations The respondent’s company position was asked in the questionnaire. All of them work as quality managers or quality coordinators, according to the information Table 1. FSSC 22000 certified plastic packaging companies, classified by sector and number of manufacturing sites in Brazil.

Nº of Companies Polyethylene covers 6 Preforms and PET bottles 8 Polyethylene films and bags 1 Polypropylene big bag 1 Thermoformed polypropylene cup 1 Polyethylene containers 3 Total 20 Sectors

Nº of Factories 8 29 1 1 3 11 53

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Cantanhede, V., Pereira, K. S., & Barreto, D. W. gathered. This piece of information increases the chances that questionnaire responses were given by employees who have a holistic view of the organization and deep knowledge of quality and product safety, that is, those who are directly involved with FSSC22000.

Out of the organizations surveyed, seven are multinationals, located in Brazil, and five of them are national companies.

Most of them have been operating in the market segment for more than ten years. According to the participating companies, nine out of the 11 companies are located in southern and southeastern Brazil. Therefore, these Brazilian regions are the places where the largest number of certified companies is found.

The size of each company was evaluated, considering the annual gross operating revenue, according to the criteria defined by BNDES (National Development Bank)[15].

Such evaluation indicated that 73% is classified as large companies, 18% medium-to-large companies and other 9% as small businesses. The majority (64%) sells in the domestic market and exports to other countries.

The number of employees of each participating organization was also evaluated. Therefore, it was found that 63% of the responding organizations have 101 to 200 employees and only 18% have over 300 employees.

Before the FSSC 22000 implementation, 80% of the companies already had some other certified management system, being at least the quality management standard ISO 9001. This one is the basis for expansion of a quality system, and its certification measures the effectiveness of the system in international standards. If the activity related to food safety was previously established, it was also analyzed.

Once these companies are packaging suppliers for food and beverages, it is common that customers require at least good manufacturing practices, which are the basic and necessary activities to ensure a hygienic and safe environment[6].

However only two out of the eleven companies responded there was not any practice implemented. These data are shown in the Table 2.

3.2 Analysis of the standard implementation process 3.2.1. Motivations for the FSSC 22000 certification Unlike other management standards, such as ISO 9001, whose certification is currently consolidated in Brazil and worldwide, as a competitive and strategic advantage, and in many cases as a contractual requirement between companies[16], FSSC 22000 is not widespread yet. This way, the certification has been recently obtained by organizations.

Thus, the intention for conquering the certification was evaluated.

The motivations for the certification of a standard can be classified into two categories: internal and external motivations. The internal one is related to the organization improvement, for example, the improvement of the management system, increased productivity, increased company’s revenue, enhanced employee awareness, reduction of non-compliance, among others. On the other hand, the external one is related to marketing, pressure applied by the customer and increased market share[17].

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Table 2. Profile of responding companies before starting the FSSC 22000 implementation.

Company

Certification (ISO)

A B C D E F G H I J L

Yes Yes Yes Yes No Yes Yes Yes Yes No Yes

Activity related to Food Safety HACCP No GMP GMP HACCP GMP GMP HACCP No HACCP GMP

GMP = Good manufacturing practices.

The survey outcomes showed that 91% of the motivations were related to external issues. Companies reported that the main factor for the decision to certify their system in the standard FSSC 220000 was related to increased competitiveness and customer retention. In the current context of the open market, it is vital that companies understand the market requirements and address their strategies to serve them and overcome them. Therefore, competitive advantages should be created based on existing patterns of competition in the market[1].

Only one of the participating companies sought the FSSC 22000 certification driven by internal reasons: product quality and safety improvement. It was found that this company is national and operates in the domestic market only, and had already been certified in other ISO management standards.

3.2.2. Difficulties in the FSSC 22000 implementation process Some obstacles to the implementation of systems, programs or quality tools may exist and need special attention of managers[17]. The main difficulties in implementing a new management standard, which are identified in the literature, are the lack of knowledge and the resistance of employees, in addition to difficulty in spreading the quality culture and high costs in the implementation of the standard[18]. Ribeiro[19], in his research with Portuguese companies, points out that the main reported challenges were the implementation of defined procedures, the resistance of employees and the need for staff training.

Table 3 shows the difficulties reported by the participating companies in relation to the process ranging from the implementation of the standard to its certification. It is noted that the difficulty in developing the HACCP study (Hazard Analysis and Critical Control Points) was stated by almost all companies.

The use of the HACCP study aims to identify and analyze the risks involved, seeking control alternatives in order to ensure the safety of the final product[20]. Thus, it is already widespread in the food industry worldwide, since it is widely recognized as the best method to ensure product safety.

As it has a very technical approach for its implementation, it becomes especially important to have theoretical and Polímeros, 28(1), 38-43, 2018

FSSC 22000 Packaging Implementation: a Plastics Industry Research Table 3. Difficulties during the FSSC 22000 implementation.

Difficulties Developing the HACCP study Resistance of employees Lack of technical knowledge of employees Short deadline High cost Documentation excess Lack of organizational infrastructure Lack of top management commitment

Nº of citations 8 4 4 4 3 2 1 0

practical knowledge. Companies, which had already been certified in any ISO, or had already implemented GMP, stated that HACCP was a difficulty. Companies reported, [...] due to lack of knowledge on the standard, employees had a lot of difficulty with the HACCP study” and that “the company had no experience in the implementation of a food safety system and had no models or examples of the required documentation. In addition, they did not have any idea about the implementation extension of the reference standard items.

The staff related the greatest difficulties: resistance and lack of technical knowledge of employees.

According to Oliveira and Pinheiro (2010), resistance to change is related to the way of people’s thinking and acting as well as organizational culture. It has been seen as one of the main obstacles to the improvement of organizations.

Its causes are related to uncertainty, self-interest threat, and different perceptions of the need for change and the lack of tolerance[21].Culture change, followed by resistance of employees, were the greatest difficulties identified in a survey conducted by INMETRO (2005), after interviewing 100 ISO 9001 certified companies[22]. Maekawa et al.[17], in his research, highlighted resistance to change by employees and low staff qualification as the major obstacles to system implementation.The resistance of employees to an organizational culture change is naturally expected to be a major challenge for the implementation of a new standard.

In fact, it can impede the proper functioning of a management system. In addition to it, the lack of technical knowledge of employees becomes a barrier in the interpretation and implementation of the requirements.

For instance, company A reported that “[...] culture change, linked to low qualification of staff, interfered in the understanding of the importance of necessary requirements and behaviors for food safety assurance.”

As suggested by authors[17], there are strategies in order to eliminate or minimize the resistance of employees.

They are: raising awareness among staff through lectures and training; clarifying and discuss the implications of the new procedures, benefits and difficulties for both company and employees; simplifying the language of documentation in order to facilitate the comprehension on all levels of operation; working closely with the human resources department during the system implementation and rewarding good performance.

Four companies as one of the difficulties experienced also cited the short deadline, from implementation to certification.

The implementation and certification of a standard requires time and dedication of employees. Ribeiro[19] also identified the short term as one of the main difficulties of ISO 9001 Polímeros, 28(1), 38-43, 2018

certified companies. She highlights the lack of time that most of the employees when devoting to implementation activities and incorporation of a new standard, because sometimes they do more than one function in the organizational structure.

She also emphasizes that other authors have also mentioned this difficulty in their papers, such as Bhuiyan and Alam[23] and Gotzamani[24].

Besides, one of the companies that “the short deadline was a difficulty in the certification process, because we had few records for audits, reported it”.

More than half of the sample implemented the system between 6 and 12 months (63%), followed by the range of 12 to 18 months with 30% of the companies. None of the participating companies exceeded one and a half year to certify the system. It was found that, among the 8 companies, which were certified in less than one year, 6 were motivated by customer demand, which can indicate the short deadline was influenced by market pressure. Market pressure can be considered as constraints placed on trade by the level of demand in the market, for example, “I just buy materials from certified companies”).

The implementation of any consequently requires a large financial investment. Although reported only by three companies, the high cost may represent a hindrance for certification of a standard, especially when considering FSSC 22000. Among the major financial investments, informants indicated the adequacy of building infrastructure and facilities (55%), the laboratory analysis services to meet legal and regulatory requirements (36%) and hiring training sessions (9%) as the main ones.

For example, company J reported, [...] the biggest challenge was related to the high cost of implementation, because it involved several expenses, both on the building infrastructure and on necessary analysis. One of them is the analytical process on packaging migration, which is to verify whether any substance in the packaging migrates into the food or beverage. This type of analysis is costly and requires investment by the company.

The high cost for implementing FSSC 22000 may be the greatest barrier for small businesses seeking to be certified, since the availability of financial resources was strongly cited by companies as essential for this conquest. Besides, studies on food chain organizations point out small businesses are less likely to have a certificated quality and safety food system due to the financial cost[20].

There was no mention of top management commitment as an experienced difficulty. Thus, one can infer that in every organization there was the support of senior management.

3.2.3. Certification outcomes The key factors, which facilitated the implementation of FSSC 22000 are seen in Table 4. Predominantly considered by eight out of the nine companies that were already certified in (an) other standard(s), having an implemented management system was a major facilitator for the implementation of FSSC 22000. Like other voluntary management standards, which are strongly influenced by ISO 9001, FSSC 22000 was too. In addition, they present very similar management system requirements.

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Cantanhede, V., Pereira, K. S., & Barreto, D. W. More than half of the companies reported that senior management commitment was essential for achieving the certification. According to the work developed by[25] and the bibliographic research, among eleven authors, the success of any quality management system primarily depends on a strong commitment of top management. One of the aspects that demonstrates this commitment is the availability of sufficient resources for related activities. The provision of adequate resources for the establishment, implementation, maintenance and updating of the food safety management system is a mandatory requirement of ISO 22000 standard[6].

As FSSC22000 requirements implementation is quite expensive, it was expected that the availability of financial resources would be one of the factors often mentioned by respondents.

Regarding consultancy hiring, eight out of the eleven companies reported having received specialized advisory.

Among those, only two reported this support as one of the certification success factors. In addition, some companies did not have any activity related to food safety previously implemented. This is an indication that the technical knowledge by those who were responsible for the standard is a key factor, as cited by three companies in the survey.

When this knowledge is not at all widespread among those who are responsible for the standard implementation, it is necessary to invest in consultancy. In addition, this service offers guidance, planned intervention in an organization and identifies existing problems, assists in strategic decisions and presents better ways to solve them, with reference to regulatory requirements, promoting impact on results in the short and long term[25].

For organizations, being certified is a very important, voluntary process, considering the fact that the adoption of management practice has an advantage mainly in the international market[26]. The certification ensures the organization keeps pursuing improvement in their administrative and production processes[27]. The implementation of FSSC 22000 brings many benefits to the organization that aims to develop its concepts and functions. The stated benefits obtained by the eleven respondent companies are presented in Table 5.

About the benefits of certification, it is essential to evaluate the motivations that led the companies to be certified.

The motivations can lead to different results depending on the level of commitment of senior management, the awareness of the existing business weaknesses and the availability of financial, physical and human resources[17].

Correlating the main reasons stated by companies seeking the FSSC 22000 certification (access to new markets and customer retention), with benefits accrued after this conquest (improvement of company’s image, new customers and access to new markets), it is noted there is relative coherence. These (food and beverages) customers have a global representation and importance in the packaging market, since most of the sales come from the food (51%) and beverages (18%) segments[28]. Similarly, in Brazil, the largest packaging consumer market is the food and beverage industry representing 74% of the domestic packaging purchase[29].

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Table 4. Key factors for the successful FSSC 22000 implementation.

Factors Already certified in (an) other standard(s) Senior management commitment Availability of financial resources Technical knowledge of the time External consulting contract

Nº of citations 7 7 6 3 2

Table 5. Benefits obtained with the FSSC 22000 certification.

Benefits Nº of citations The awareness of employees 7 Improvement of company’s image 6 Improvement of quality and safety of this products 6 New customers and access to new markets 5 Increased customer satisfaction 4 Improvement internal organizational 3 Improvement comunication 3 Increased productivity 2 Reduction of non-compliant products 2

Therefore, it is concluded that being FSSC 22000 certified allows the organization to adapt to market competition standards, a factor that contributes to its competitiveness.

Interestingly, although internal organizational factors were not the certification drivers for some companies, the awareness of employees in relation to product safety and quality improvement was considered among the three major benefits for the organizations, that is, once overcoming the resistance of employees, this aspect becomes a benefit to the organization.

The participating companies were also asked about the level of satisfaction, considering the initial motivations for implementing FSSC 222000 and the results after the certification of this standard. According to their answers (55% satisfied and 45% very satisfied), it can be concluded that all companies are at least satisfied.

4. Conclusion This paper has enabled progress in mapping and understanding the reality of plastic packaging manufacturers for food and beverages, which are certified according to standard FSSC 220000. It was concluded that, among the reasons that led the companies to seek the certification, the main one was to improve competitiveness and customer retention. The greatest difficulties were related to personnel, which presented technical and behavioral issues. In addition, it was noticed that an overall satisfaction, derived from after‑certification benefits, have been arisen in the companies.

For instance, an increase in employee awareness, improvement of the company’s image and conquest the new customers, significantly contributing to their competitiveness, are some of the benefits found in this process.

The capacity of a product to meet the customer’s stated or implied needs through its features[30], i.e., having the assured quality, has long been the key to satisfaction and maintenance of customers in the packaging industry.

However, in the current scenario, to be well positioned in the Polímeros, 28(1), 38-43, 2018

FSSC 22000 Packaging Implementation: a Plastics Industry Research market, it is not enough. After FSSC 22000 was published, some of the large food and beverage organizations started demanding the proof of this certification when hiring their suppliers, which became a strong market trend. This fact confirms that FSSC 22000 influences and will influence competitiveness of packaging companies. The presented panorama can support companies that want to develop this type of system and can motivate many organizations to obtain the FSSC 22000 certification, due to the positive data presented here.

5. References 1. Carvalho, J. L. M., & Toledo, J. C. (2002). A Contribuição dos Programas da Qualidade na Competitividade: estudo de caso no mercado brasileiro de polipropileno. Polímeros: Ciência e Tecnologia, 12(4), 240-247. http://dx.doi.org/10.1590/S010414282002000400006.

2. Carvalho, J. L. M., & Toledo, J. C. (2000). Restruturação Produtiva, Programas da Qualidade e Certificações ISO 9000 e ISO 14000 em Empresas Brasileiras: pesquisa no setor químico/ petroquímico. Polímeros: Ciência e Tecnologia, 10(4), 179192. http://dx.doi.org/10.1590/S0104-14282000000400005.

3. Garcia, R. W. D. (2003). Reflexos da globalização na cultura alimentar: considerações sobre as mudanças na alimentação urbana. Revista de Nutrição, 16(4), 483-492. http://dx.doi. org/10.1590/S1415-52732003000400011.

4. Associação Brasileira das Indústrias de Alimentação - ABIA. (2010). Principais exportadores mundiais de alimentos. São Paulo. Retrieved in 2016, May 26, from http://abia.org.br/vst/ SugestoesINDALparaAlavancagemExportacaoAlimsProcessados. pdf 5. Associação Brasileira das Indústrias de Alimentação ABIA. (2012). A Força do Setor de Alimentos. São Paulo.

Retrieved in 2016, May 26, from http://abia.org.br/vst/ AForcadoSetordeAlimentos.pdf 6. Associação Brasileira de Normas Técnicas – ABNT. (2006).

Norma Técnica NBR ISO 22000. Sistema de Gestão da Segurança de alimentos: requisitos para qualquer organização na cadeia produtiva de alimentos. São Paulo: ABNT. 7. Vieira, A. C. P. (2009). Instituições e segurança dos alimentos: construindo uma nova institucionalidade (Doctoral thesis).

Universidade Estadual de Campinas, Campinas.

8. Wallis, G., Weil, D., & Madi, L. F. C. (2012). O Mercado de Embalagem no Brasil. Brasil Pack Trends, 2020, 9-39.

9. DATAMARK. (2015). Mercado de embalagem em 2014.

Retrieved in 2015, September 20, from http://www.datamark. com.br/dados-gerais 10. Associação Brasileira de Embalagens – ABRE. (2015). Estudo macroeconômico da embalagem. São Paulo. Retrieved in 2016, May 26, from http://www.abre.org.br/setor/dados-de-mercado 11. Foundation for Food Safety Certification – FSSC. (2015).

Certificação de Sistemas de Gestão de Segurança dos Alimentos 22000. Retrieved in 2015, November 11, from http://fssc22000. com/downloads/brochurefssc22000_po.pdf 12. Foundation for Food Safety Certification – FSSC. (2015).

Certificates Directory. Retrieved in 2015, July 21, from http:// www.fssc22000.com/documents/certified-organizations. xml?lang=en 13. Sampieri, R. H., Collado, C. F., & Lucio, P. B. (2006).

Metodologia de pesquisa. São Paulo: McGrawHill.

14. Cooper, D. R., & Schindler, P. S. (2011). Métodos de Pesquisa em Administração. Porto Alegre: Bookman.

15. Banco Nacional do Desenvolvimento – BNDES (2012).

Porte de empresa. Rio de Janeiro. Retrieved in 2015, July 25, Polímeros, 28(1), 38-43, 2018

from http://www.bndes.gov.br/SiteBNDES/bndes/bndes_pt/ Institucional/Apoio_Financeiro/porte.html 16. Viera, A., Caraschi, J. C., & Prates, G. A. (2014). Implantação do certificado ISO 9001 em uma empresa no setor de papelão: avaliando seus impactos organizacionais. Brazilian Journal of Biosystems Engineering, 8(3), 263-270. http://dx.doi. org/10.18011/bioeng2014v8n3p263-270.

17. Maekawa, R., Carvalho, M. M., & Oliveira, O. J. (2013). Um estudo sobre a certificação ISO 9001 no Brasil: mapeamento de motivações, benefícios e dificuldades. Gestão & Produção, 20(4), 763-779. http://dx.doi.org/10.1590/S0104-530X2013005000003.

18. Silva, M. T. S., Jr. (2013). Benefícios e dificuldades na adoção de um sistema de gestão da qualidade no Rio Grande do Norte (Master’s thesis). Universidade Federal do Rio Grande do Norte, Natal.

19. Ribeiro, S. I. (2012). Os benefícios e as dificuldades na certificação da qualidade – Norma NP EN ISO 9001:2008 (Master’s thesis). Instituto Politécnico do Porto, São Mamede de Infesta, Porto.

20. Paula, S. L., & Ravagnani, M. A. S. S. (2009). Lógica Fuzzy como Ferramenta de Decisão na Identificação dos Perigos Significativos e Medidas Preventivas de Controle do Sistema APPCC (Doctoral dissertation). Universidade Estadual de Maringá, Maringá.

21. Oliveira, O. J., & Pinheiro, C. R. M. S. (2010). Implantação de sistemas de gestão ambiental ISO 14001: uma contribuição da área de gestão de pessoas. Gestão & Produção, 17(1), 51-61. http://dx.doi.org/10.1590/S0104-530X2010000100005.

22. Instituto Nacional de Metrologia – INMETRO. (2005). Qualidade e Tecnologia. Pesquisa de credibilidade das certificações ISO9001. Retrieved in 2016, June 16, from http://www.inmetro. gov.br/qualidade/pdf/Apresentacao_CB25_Rev0.pdf 23. Bhuiyan, N., & Alam, N. (2005). An investigation into issues related to the latest version of ISO 9000. Total Quality Management & Business Excellence, 16(2), 199-213. http:// dx.doi.org/10.1080/14783360500054343.

24. Gotzamani, K. (2010). Results of an empirical investigation on the anticipated improvement areas of the ISO 9001:2000 standard. Total Quality Management & Business Excellence, 21(6), 687-704. http://dx.doi.org/10.1080/14783363.2010.48 3101.

25. Soriano, D. R. (2001). Quality in the consulting service – evaluation and impact: a survey in Spanish firms. Managing Service Quality, 11(1), 40-48. http://dx.doi.org/10.1108/09604520110359366.

26. Soares, M. F. (2013). Análise de integração em sistemas de gestão baseados nas Normas ISO 9001, ISO 14001 e OHSAS 18001 em empresas de construção civil (Master’s thesis).

Universidade Federal do Ceará, Fortaleza.

27. Carvalho, M. M., & Paladini, E. P. (2012). Gestão da qualidade: teoria e casos. Rio de Janeiro: Elsevier.

28. Wallis, G., Weil, D., & Madi, L. F. C. (2012). O mercado de embalagem: mundo e Brasil. In C. I. G. L. Sarantópoulos, R. A. Rego (Eds.), Brasil Pack Trends 2020 (pp. 9-39). Campinas: ITAL. 29. DATAMARK. (2015). Mercado de Embalagem 2012. Retrieved in 2015, October 12, from http://www.datamark.com.br/dadosgerais 30. Associação Brasileira de Normas Técnicas – ABNT. (2008).

Norma Técnica NBR ISO 9001. Sistema de Gestão da Qualidade – Requisitos. São Paulo: ABNT. Received: May 23, 2016 Revised: Mar. 15, 2017 Accepted: Apr. 04, 2017 43/43 43

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.09516

O O O O O O O O O O O O O O O O

Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends Ricardo Mesias1 and Edwin Murillo2* Grupo de Investigación materiales poliméricos, Universidad de Antioquia, Medellín, Colombia 2 Grupo de Investigación en Materiales Poliméricos (GIMAPOL), Departamento de Química, Universidad Francisco de Paula Santander, San José de Cúcuta, Colombia

1

*edwinalbertomr@ufps.edu.co

Abstract A hyperbranched polyester polyol of the second generation (HBP2) was modified with polylactic acid (HBP2-g-PLA) and employed as a compatibilizer for plasticized tapioca starch (TPS)/polylactic acid (PLA) blends. The effect of the compatibilizer HBP2-g-PLA was evaluated in comparison to the control sample (TPS/PLA blend without HBP2-g‑PLA).

The torque value of the TPS/PLA blends with HBP2-g-PLA was lower than that of the control sample, while thermal stability and crystallinity followed opposite behavior. The glass transition temperature (Tg) and degree of crystallinity of the TPS/PLA blends with HBP2-g-PLA decreased with increasing mass fraction of HBP2-g-PLA. By scanning electron microscopy (SEM), it was observed that the morphology of the TPS/PLA blends with HBP2-g-PLA was more homogeneous than that of the control sample, confirming that HBP2-g-PLA acted as a compatibilizer and plasticizing agent to the TPS/PLA blends. Rheological analysis of the compatibilized TPS/PLA blends indicated the presence of microstructure.

Keywords: biodegradable polymers, hyperbranched polyester, compatibilization, thermoplastic starch/PLA blend, properties.

1. Introduction The environmental impact caused by conventional non-biodegradable polymeric materials waste has created the need to develop sustainable polymeric materials from renewable resources, since alternative methods of recycling and disposal of non-biodegradable polymeric materials have not been fully effective[1,2]. Petrochemical resources are non-renewable and are continuously depleted, so it is important to find sustainable substitutes; especially for disposable packaging applications with a short time of use[3].

The starch has granular form and it is not a thermoplastic polymer. Therefore, for obtaining thermoplastic starch, it has to be plasticized[4,5]. The typically used plasticizing agents are hydrophilic. Some of these are urea, ethanolamine, glycerol and sorbitol[6]. The material obtained has poor mechanical properties as compared to polymers derived from petrochemical sources[1,6]. One way to improve mechanical properties and maintain the biodegradability properties consists in mixing starch with PLA, which is hydrophobic, biodegradable, and it has good processability and mechanical properties (high tensile modulus and tensile strength)[7,8]. The incompatibility of the hydrophobic aliphatic polyesters (for example PLA) and starch makes a weak adhesion between the two components[3], which results in low mechanical properties of this mixture[9,10]. In order to improve compatibility between the two phases and the physicochemical properties of the starch/PLA blends, different strategies of compatibilization have been developed[9,11]. PLA/starch modified with maleic

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anhydride (starch-g-MA) blends were prepared, however, they exhibited poor interfacial adhesion, which was due to the hydrophobicity of PLA and the hydrophilicity of starch-g-MA[10]. PLA was blended with starch, plasticized with glycerol, and the morphology of the materials obtained was very coarse (TPS particles sizes between 5 and 30 μm).

But when PLA was replaced with PLA modified with MA (PLA-g-MA) the particle size was in the 1-3 μm range[12].

Starch/PLA blends were obtained by using epoxidized soybean oil (ESO) as a reactive compatibilizer agent.

The starch granules were grafted with MA to enhance its reactivity with ESO. The blends prepared were compatible[13].

Starch/PLA blends were obtained employing three strategies of compatibilization: 1. Formation of urethane bonds in-situ, 2. Crosslinking between starch and PLA, and 3. Addition of PLA grafted amylose. Better results were obtained by using PLA grafted amylose as compatibilizer agent[3].

The hyperbranched polyester polyols (HBP) possess structures with a high structural packing and great number of OH groups. They also have low viscosity in solution and molten state, a lower degree of molecular entanglements than linear polymers of the same molar mass, and they are not toxic[14-21]. These materials may be a good alternative to obtain compatibilizer agents by modification of OH groups with other compounds such as amine, isocyanate, acids, etc.

In a previous study[21], HBP2 was modified with different proportions of PLA to obtain materials (for example, HBP2-g-PLA) that may be employed for studies of the

Polímeros, 28(1), 44-52, 2018

Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends compatibilization of starch/PLA blends, since there are OH and PLA units on the periphery of this material.

Additionally, this material has low viscosity (lower than 1 Pa.s) due to small hydrodynamic dimensions in solution and possibly it may be located at the interface between starch and PLA[21]. Thus, HBP2-g-PLA possibly acts as a plasticizing agent to this blend.

As was already mentioned, the materials usually employed for the compatibilization of starch/PLA blends are linear structures with low functionality. However, taking the structure of HBP2-g-PLA into account[21], this material may possibly act as a compatibilizer agent for TPS/PLA blends, since PLA and OH groups of HBP2-g-PLA can interact with PLA as well as TPS, respectively (Figure 1).

In order to make effective compatibilization of the TPS/PLA blends, HBP2-g-PLA may be used as a new alternative. Therefore, the aim of this study was to evaluate the compatibilizer effect of HBP2-g-PLA in a TPS/PLA blend (50/50 wt%). Furthermore, the structure to properties relationship was investigated for different proportions of HBP2-g-PLA and TPS/PLA blends considering their structural, thermal, rheological, morphological and mechanical properties. Additionally, in this study the neat PLA was not processed under the same condition of the TPS/PLA blends.

2. Experimental Part 2.1 Materials The PLA with the number average molar mass (Mn) 68.000 g/mol and acid value of 51.72 mg KOH/g was supplied by the company ALICO from Colombia. TPS (Plasticized tapioca starch) was previously prepared in our laboratory (60 wt% of tapioca starch and 40 wt% of sorbitol) by using a torque rheometer Thermo Science at 150 °C and rotation speed of 50 rpm. HBP2-g-PLA was synthesized as described in a previous study[21] by an esterification reaction, employing 45 wt % of HBP2 and 55 wt % of PLA[21]. In that work[21], this material was named HBP2G45 and the characteristics are as follows: acid value: 8.99 mg KOH/g, hydroxyl value: 172.48 mg KOH/g, decomposition temperature (T d): 243.1 °C and Tg: 42.8 °C[21].

2.2 Preparation of the samples The respective proportions of TPS, PLA and HBP2‑g‑PLA were weighed and homogenized in a container, and measured by torque rheometer Thermo Science at 200 °C. The rheometer was kept at a rotation speed of 50 rpm. The mixing time was 5 min. In all cases the mass ratio of TPS and PLA was 50/50 wt%. The amount of HBP2-g-PLA utilized were 5 wt% (Blend1), 10 wt% (Blend2), 15 wt% (Blend3) and 20 wt% (Blend4) with respect to the total amount of TPS and PLA. To evaluate the compatibilizing efficiency of the HBP2‑g‑PLA in the TPS/PLA blends, a control blend (TPS/PLA 50/50 wt%) without HBP2-g-PLA was prepared under the same conditions used for preparation of TPS/PLA blends with HBP2-g-PLA.

2.3 Characterization The thermal stability of the samples was evaluated by thermogravimetric analysis (TGA) on a TA Instruments model Q-500 employing nitrogen atmosphere. The materials (around 20 mg) were heated from room temperature to 600 °C, utilizing a heating rate of 10 °C/min. Differential scanning calorimetry (DSC) measurements were performed on a TA Instruments model Q100 equipped with a cooling and heating system. The samples (around 10 mg) were heated at a heating rate of 40 °C/min from room temperature to 250 °C, followed by an isotherm for 5 min. The sample was then cooled to -80 °C, using a cooling rate of 40 °C/min and equilibrated at -80 °C (first scan). The second heating scan was in the temperature range between -80 °C to 250 °C by using a heating rate of 20 °C/min. In all cases a nitrogen atmosphere was used. The Tg, melting temperature (Tm) and melting enthalpy (ΔHm) were determined from the second heating scan. The samples (granules) for X ray diffraction (XRD) analysis were placed in a desiccator for 24 h.

The XRD analysis was performed on a PANalytical X’Pert PRO MPD diffractometer by using Cu-K alpha radiation (λ=1.5406 Å). The voltage and operating current were 45 kV and 40 mA, respectively. The sweep was done between 10 and 70 degrees with steps of 0.013 degrees and a step time of 59 s. The samples for SEM analysis were placed in a desiccator for 24 h. They were then fractured under liquid nitrogen, and finally were coated with gold. SEM analysis was done using a microscope JEOL JSM‑6490LV at an acceleration voltage of 5 kV. In order to perform rheological analysis, a rotational rheometer of Malvern Instruments was employed, using a cone-plate geometry with a constant gap setting of 1 mm. The oscillatory analysis was performed by using strain of 0.01% at angular frequency between 0.1 and 100 Hz. All measurements were performed at 200 °C. For tensile analysis the type IV specimens were prepared in an Implejoy injection machine. About 25 g sample was put into the cylinder for 5 min. and kept at 200 °C and then molded by using a piston. The mechanical properties according to ASTM D 638 standard were determined on a universal machine brand Digimess at a deformation rate of 5 mm/min.

3. Results and Discussions

Figure 1. Schematic representation of the interactions of TPS and PLA with the HBP2-g-PLA. Polímeros, 28(1), 44-52, 2018

Figure 2 presents the torque vs time graph (Figure 2a) and the temperature vs time graph (Figure 2b). It can be observed (Figure 2a), that all the samples exhibited an increase in torque value after the first minute of mixing 45/52 45

Mesias, R., & Murillo, E.

Figure 2. Torque rheometry of the TPS/PLA blends and control sample: (a) torque vs time, (b) temperature vs time.

process. The control sample showed the highest torque value (156.4 Nm) indicating the highest viscosity of all samples.

The TPS/PLA blends with HBP2-g-PLA exhibited much lower torque value in comparison to the control sample; this observation implies the plasticizing effect of HBP2-g-PLA on the TPS/PLA blends. In all cases, the torque stabilized at about 4.5 min of mixing, which can be taken as the optimum mixing time. The first increase of the torque is due to the melting process of the sample. The second increase on the torque value is possibly due to increase of interactions and rearrangement of the TPS. It was observed that the second increase on torque value reached a stable value, therefore the degradation process was not observed. The second increase on torque value due to the Blend1 appeared after two minutes. It is possibly attributed to a low proportion of the HBP2-g-PLA, which was employed during the preparation of this blend, since there is low interactions and rearrangement of the starch granules.

The final torque values did not exceed 50 Nm. The final torque values obtained for blends of PLA/thermoplastic acetylated starch (5-10 Nm)[1], are comparable to that of the Blend1 (5.90) Nm) and Blend2 (5.58. Nm), but are higher than those of the Blend3 (2.6 Nm) and Blend4 (2.3 Nm).

All blends reduced the initial temperature gradually (Figure 2b).

The control sample showed a reduction in temperature with respect to the TPS/PLA blends with HBP2-g-PLA, indicating that the presence of HBP2-g-PLA required an additional energy to melt. Therefore, an increase in torque (Figure 2a) is a result of not completely melted samples, which is also reflected in reduced sample temperature. These results are important because the processing temperature of TPS/PLA blends with HBP2-g-PLA is reduced as compared to the control sample.

TGA and DSC thermograms of samples are presented in Figure 3, while the Td values of the samples, obtained at 10% of weight loss, are presented in Table 1. Figure 3a and 3b show the TGA thermograms of the samples. TPS shows a small weight loss (8.18%) between 100 and 200 °C and this can be attributed to evaporation of water due to the 46 46/52

Table 1. Values of Tg, Tm and Td of the samples.

Sample

Td (°C)

Tg (°C)

Tm (°C)

TPS Control Blend1 Blend2 Blend3 Blend4

264 301 289 285 280 281

26.1 59.6 57.4 49.8 48.0 43.3

-153.1 152.1 150.8 -

ΔHm (J/g) 2.6 2.5 1.0 -

Xc (%) 5.6 5.4 2.2 -

presence of humidity. Additionally, TPS shows another significant weight loss at 264 °C. The thermal stability of the control sample is higher than that of the TPS/PLA blends with HBP2-g-PLA (Figures 3a and 3b). This behavior can be attributed to low thermal stability of HBP2-g-PLA (243.1 °C)[21] or a closer interaction between the TPS and PLA could facilitate faster PLA degradation. This also has been observed in starch/PLA blends using butyl-etherified wax as a compatibilizer agent[22]. Furthermore, some authors have demonstrated that TPS tends to reduce the thermal stability of PLA[22,23], which is caused by the moisture.

The Td of the PLA on the TPS/PLA blends with HBP2‑g‑PLA was lower than that of neat PLA (332 °C)[21], it can be attributed to the processing, since it has been demonstrated that the thermal stability of PLA is slightly reduced by processing. The mechanism of the degradation of PLA has been attributed to depolymerization by intramolecular transesterification and it occurs between 270 and 360 °C [24].

The TGA thermograms did not exhibit the Td of the HBP2-g-PLA (243.1 °C) and this may be associated with the low amount of HBP2-g-PLA employed or the interactions of HBP2-g-PLA with other components in the blends. Additionally, the Td values of the TPS/PLA blends with HBP2-g-PLA do not show dependence on the amount of HBP2-g-PLA employed (up to 20 wt%). This can be interpreted by differences in the degree of interaction between the materials (TPS, PLA and HBP2-g-PLA) or probably differences in degradation mechanisms[22,23]. The Blend3 Polímeros, 28(1), 44-52, 2018

Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends

Figure 3. TGA and DSC Thermograms (a) Weight vs. temperature, (b) Deriv. weight vs. temperature, (c) Heat flow vs. temperature.

exhibited two peaks (Figure 3b); it is attributed possibly to the formation of some structure of low mass molar, which was formed by hydroxyl-ester interchange reaction, it has been reported for hyperbranched polyesters[19].

DSC analysis was performed in order to identify thermal transitions and possible changes in Tg. The control sample exhibits a Tg value of 59.6 °C (Figure 3c), which is higher than that of neat PLA (57.6 °C)[21] and neat TPS (26 °C) meaning that TPS restricts mobility of PLA chains in this sample and that a new structural arrangement or interaction possibly occur. Additionally, it also may be due to the migration of sorbitol present in TPS. The Tg value of the control sample is also higher than that of the TPS/PLA blends with HBP2-g-PLA, which follow the trend of an decrease with the HBP2-g-PLA content (Figure 3c and Table 1). In the case of the Blend3 and Blend4, it is due to improved miscibility of the components[1], because the PLA crystalline domains disappear. But in the case of blend 1 and Blend2, it is due to a plasticizing effect of HBP2-g-PLA, which is also supported by the lowest viscosity in the molten state (lower than 1 Pa.s)[21] and by the torque rheometry study (Figure 1). A similar effect of starch/PLA blends was reported for MA[25]. Jang et al.[26] observed a reduction of Tg value of starch/PLA blends compatibilized with MA, but the variations were larger than 6 °C in relation to neat PLA. The Tg values are the lowest for Blend3 and Blend4 and allow to infer that these blends present the highest compatibilization degree and miscibility. The absence of the Tg of the HBP2-g-PLA (42.8 °C)[21] in the TPS/PLA Polímeros, 28(1), 44-52, 2018

blends thermograms, could not be observed due to the low difference between the Tg values.

Tm of the PLA in the control sample is lower than that of neat PLA (156.7 °C)[21]. Therefore, TPS reduces structural packing. Tm of the control sample was slightly higher than those of the Blend1 and Blend2 (Table 1). Blend3 and Blend4 did not exhibit Tbbbm, which indicates that these blends increased ostensibly the degree of structural disorder, since their crystalline nature was reduced. The conclusion to be drawn from these results is that the Blend3 and Blend4 present a high compatibilization degree.

In a study of compatibilization of the starch/PLA blends three different strategies have been reported: a) in situ formation of urethane linkages; b) coupling with peroxide between starch and PLA, and (c) the addition of PLA-grafted amylose as a compatibilizer; in all cases the Tm of the PLA was observed[3].

The degree of crystallinity of the samples was determined by employing the following Equation 1[26]: Xc = ( ∆H m / ∅ PLA ) / ∆H m0 ×100

(1)

Where X c , ∆H m, ∅ PLA and ∆H m0 are the crystallinity percent, the melting enthalpy, the weight fraction of PLA in the blends and the melting enthalpy of a crystal of infinite size of PLA (93.6 J/g) respectively[3]. The degree of crystallinity of the samples was calculated as a function of PLA content.

The control sample showed higher degree of crystallinity than the TPS/PLA blends with HBP2-g-PLA (Table 1).

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Mesias, R., & Murillo, E. Among the TPS/PLA blends with HBP2-g-PLA, Blend1 with the lowest amount of HBP2-g-PLA showed the highest values of ∆H m, and X c, which indicates that this sample has a greater number of crystals (Table 1). HBP2-g-PLA thus affected the crystallinity of the PLA in the TPS/PLA blends enormously. This is possibly attributed to HBP2-g-PLA, which restricts the structural packing of the PLA, and since it is an amorphous molecule, it increases the molecular disorder in PLA. According to the literature reviewed, we could not find evidence for any similar case, where the Tm of TPS/PLA or starch/PLA blends did not appear. This is important because it allows concluding that HBP2-g-PLA may be a good alternative for the compatibilization of starch/PLA or TPS/PLA blends[27].

Figure 4 shows the XRD patterns of the neat TPS and PLA, control sample and TPS/PLA blends (with HBP2‑g‑PLA).

TPS exhibits a wide peak between 2θ = 12.5 and 30°; it is associated with the C type crystallinity present in TPS[5].

In this 2θ range, the peak can be also attributed to V type crystallinity (2θ= 21°), which has been identified for starch plasticized with ethanolamine[28] and glycerol[29]. In the control sample, the intensity of this peak is appreciably reduced, indicating that in the TPS/PLA blends with HBP2-g-PLA some degree of interaction between these materials exists (TPS, HBP2-g-PLA, sorbitol and PLA). Neat PLA exhibits peaks at 2θ=16.8º, 19.5º and 22.3º, which are associated with the α crystalline system[30,31]. In the case of the TPS/PLA blends with HBP2-g-PLA, the PLA peak intensities decreased significantly. Blend2, Blend3 and Blend4 exhibited peaks at 2θ=16.8 and 19.5º, but the peak at 22.3° was not observed.

These results are in accordance to those of DSC analysis, since it has been shown that the degree of crystallinity of these materials is reduced as compared to the control sample.

Furthermore, it confirms once more that HBP2-g-PLA is a good compatibilizer agent to TPS/PLA blends, especially when it is used in proportions of 15 and 20 wt% (the lowest crystallinity of PLA and significant lowering of Tg value).

Figure 5 shows the SEM micrographs of the cryofractured samples. TPS exhibits a homogenous surface (Figure 5a), while the control sample (Figure 5b) presents a discontinuous phase with rounded structures, which is attributed to the

Figure 4. Difractograms of the samples.

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starch granules. Hypothetically, this is attributed to possible migration of sorbitol, employed as plasticizing agent for starch, to PLA or interface. In addition, cracks were observed in the control sample, which indicates a fragile fracture of this sample. The same behavior was exhibited by blends of PLA with maleate starch[30], acetylated starch[1] and corn starch[32].

Blend1 (Figure 5c) shows the presence of a discontinuous phase with fractured zones in the interface and in the starch granules, which suggests limited miscibility of the components.

Blend2 (Figure 5d) presents a homogeneous phase with fractures due to the presence of fine pores, which were due to the presence of volatile compounds that evaporated by the application of a vacuum. Compatibility of Blend2 (Figure 5d) is better than that of Blend1 (Figure 5c), since the fractured starch granules are not observed. Figure 5e (Blend3) shows a homogeneous phase in the presence of starch granules and fragments displayed on the surface, which could be due to tearing the matrix during sample preparation. Nevertheless, it shows good homogeneity. Blend4 (Figure 5e) presents a slight fracture at the interface, but this sample shows good homogenization. Furthermore, no domains were observed for this sample. These results are consistent with the DSC analysis and it can be concluded that the TPS/PLA blends with HBP2-g-PLA show good homogeneity and that HBP2-g-PLA exhibits a good compatibilizer effect on TPS/PLA blends.

In the starch/PLA blends, compatibilized with MA (3 wt%) and maleated thermoplastic starch (5, 10 and 15 wt%), domains of starch and PLA were observed. All blends exhibited cavities[33]. Therefore, all these blends were immiscible.

In another study, it was observed for corn TPS/PLA blends that dispersion between the two phases (TPS and PLA) increased with increasing formamide content[34]. The same was evidenced when citric acid was used as a compatibilizer agent to TPS/PLA blends[35]. The control sample, Blend3 and Blend4 were selected for rheological measurements to study the plasticizing effect of HBP2-g-PLA in these blends. Both TPS/PLA blends have the best compatibilization degree, the lowest crystallization degree of PLA and lower Tg value as compared to the control sample.

The rheological behavior of the blends is presented in Figure 6. For all samples a reduction of complex viscosity (Figure 6a) with the increasing angular frequency can be observed (pseudoplastic behavior), which is attributed to interaction rupture and disentanglement of the chains.

The complex viscosity decreases with increased HBP2‑g‑PLA content meaning that HBP2-g-PLA acts as a plasticizing agent for these blends, which can be supported by the highest viscosity exhibited by the control sample in the range of angular frequency studied. In a recent study, TPS/PLA blends exhibited a Newtonian behavior between 1 and 10 Hz, which was attributed to lower extent of interaction and entanglement of these blends[1]. Rheological results are in accordance with those obtained by torque rheometry. The reduction in viscosity of the TPS/PLA blends with HBP2-g-PLA facilitates the processability of the materials. The complex viscosity of the samples showed first a decrease and then an increase at different angular frequency values, for control sample at 100 Hz, Blend3 at 31.62 Hz and Blend4 at 25.2 Hz (Figure 6a). This is ascribed to the formation of a microstructure, which is able to deform elastically when it Polímeros, 28(1), 44-52, 2018

Hyperbranched polyester polyol modified with polylactic acid as a compatibilizer for plasticized tapioca starch/polylactic acid blends

Figure 5. SEM micrographs of the samples: (a) TPS, (b) Control sample, (c) Blend1, (d) Blend2, (e) Blend3, (f) Blend4.

Figure 6. Rheological behavior of the control sample, Blend3 and Blend4: (a) complex viscosity vs. angular frequency, (b) G’ and G” vs. angular frequency.

is exposed to external stress. This process has already been observed by several authors and is attributed to the formation of strong interactions[14,36]. It is worth noting that the control sample exhibited a higher value of angular frequency at the beginning of an increase of complex viscosity than those for Blend3 and Blend4 (Figure 6a). Therefore, it can be inferred that the presence of HBP2-g-PLA favored the formation of microstructure, which is most probably due to onset of interactions between TPS, HBP2-g-PLA and PLA, which is corroborated by faster formation of microstructure Polímeros, 28(1), 44-52, 2018

in Blend4 (20 wt% HBP2-g-PLA) than Blend3 (15 wt% HBP2-g-PLA).

Figure 6b shows behavior of elastic (G’) and viscous (G”) moduli of the control sample, Blend3 and Blend4.

The behavior of the control sample was viscoelastic with a predominant elastic contribution in contrast to the TPS/PLA blends with HBP2-g-PLA with higher viscous contribution.

Namely, the transition from elastic to viscous behavior (G’ < G”) was not observed for the control sample. It is possible that this transition occurs at an angular frequency 49/52 49

Mesias, R., & Murillo, E.

Figure 7. Mechanical properties of the samples: (a) Tensile modulus, (b) Tensile strength, (c) elongation at break.

higher than 100 Hz. Thus Blend3 and Blend4 exhibit more viscous rheological behavior as compared to the control sample, due to plasticizing effect of the HBP2-g-PLA. Additionally, in Figure 6b, two transitions can be observed for the Blend3 and Blend4. The first one corresponds to the transition from elastic to viscous response, and the second one from viscous to elastic response. This result confirms the formation of a microstructure, which is able to deform elastically and therefore supports the explanation presented above.

The tensile modulus (Figure 7a) and tensile strength (Figure 7b) of the control sample was higher than those of the TPS/PLA blends with HBP2-g-PLA. The tensile modulus and tensile strength of the blends decreased while the elongation at break increased with the proportion of the HBP2-g-PLA (Figure 7c) indicating a reduction of crystalline phase and increasing mobility of the chains. These results are in accordance with those obtained by DSC analysis, where the Tg was also reduced with the proportion of HBP2g-PLA. The value of tensile modulus of the control sample is similar to that of the TPS/PLA blends compatibilized with PLA‑grafted amylose (340 MPa)[3]. The values of tensile strength obtained in this study are comparable with those obtained for compatibilized TPS/PLA (50/50), whose values were between 10 and 20 MPa[9]. The elongation at break values of the samples are higher than those of the compatibilized TPS/PLA blends (lower than 10%), which were compatibilized employing benzoyl peroxide, 4,4-methylenbis (phenyl isocyanate) and PLA-grafted amylose[3].

50 50/52

4. Conclusions This study makes an important contribution to the art state of these materials. The thermal stability of the TPS/PLA blends with HBP2-g-PLA did follow a trend with the proportion of HBP2-g-PLA employed. DSC analysis showed that Blend1 and Blend2 presented a Tm and Tg, but Blend3 and Blend4 only exhibited a Tg. The reduction on Tg value of the blends with the content of HBP2-g-PLA is an indication that HBP2-g-PLA acts as plasticizing agent. XRD analysis showed that for the TPS/PLA blends with HBP2-gPLA, the peak of PLA associated to α crystallinity reduced its intensity. The rheological behavior of the Blend3 and Blend4 was pseudoplastic. Furthermore, the flow behavior of the control sample was more elastic than those of the TPS/ PLA blends with HBP2-g-PLA. The use of HBP2-g-PLA as compatibilizer agent of the blends of TPS/PLA (50/50 wt%) evidently changed rheological behavior of these blends.

We have demonstrated that HBP2-g-PLA can act as plasticizing and compatibilizer agent for the TPS/PLA blends.

Conventional compatibilizer agents traditionally employed for the compatibilization of TPS/PLA blends, act only as compatibilizer agents. Furthermore the compatibilization degree is usually low. Therefore, according to the results obtained in this study, HBP2-g-PLA may be an alternative for compatibility of TPS/PLA blends.

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Received: July 26, 2016 Revised: Apr. 04, 2017 Accepted: Apr. 27, 2017

PolĂ­meros, 28(1), 44-52, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.04916

Stabilization of guava nectar with hydrocolloids and pectinases Fernanda Döring Krumreich1*, Ana Paula Antunes Corrêa2, Jair Costa Nachtigal2, Gerson Lübke Buss3, Josiane Kuhn Rutz1, Michele Maciel Crizel-Cardozo1, Cristina Jansen1 and Rui Carlos Zambiazi1 Post Graduate Program of Food Science and Technology, Faculty of Agronomy Eliseu Maciel, Universidade Federal de Pelotas – UFPel, Pelotas, RS, Brazil 2 Empresa Brasileira de Pesquisa Agropecuária – Embrapa, Pelotas, RS, Brazil 3 Post Graduate Program Agronomy/Soil, Faculty of Agronomy Eliseu Maciel, Universidade Federal de Pelotas – UFPel, Pelotas, RS, Brazil 1

*nandaalimentos@gmail.com

Abstract The aim of this study was to stabilize guava nectar using hydrocolloids and/or enzymes, and evaluate the stability and the bioactive compounds content during storage. In general, there was a decrease in pH and an increase in titratable acidity and soluble solids of the nectars. During storage, it was observed that nectars with pectinase showed decrease in pH, increase in titratable acidity and soluble solids, and also less phase separation, standing out among them the nectar with enzyme and guar gum. The nectar formulated with xanthan showed the highest antioxidant capacity. All nectars showed slight decrease in the carotenoid content and high losses of vitamin C during the storage period.

Keywords: bioactives, hydrocolloids, nectar, pectinases.

1. Introduction Guava belongs to the Myrtaceae family, genus Psidium, which comprises up to 130 species of which only guava Psidium guajava L. has economic importance[1]. Guava fruits ripen quickly and have a shelf life up to 8 days, thus the processing technology can ensure the excess of production and exploitation in off-season periods[2]. Although the fruit is used for production of juices, pulps and nectars, as well as jams, jellies, fruit preserves, purees, syrups, wines, among others[3]. According to ABIR[4], the demand for nectars is growing in Brazil. The Ministry of Agriculture and Supply, which is the regulatory agency of the processing industries of juices and fruit nectars and identity standards[5] defines guava nectar as a non-fermented beverage produced by dissolution of guava pulp (Psidium guajava L.) and sugars in drinking water, intended for direct consumption, with or without addition of acids. The attributes color and turbidity are decisive for the acceptance of juices and nectars, which should not present sedimentation or phase separation, even with preservation of the nutritional value and taste[6]. Phase separation is associated with chemical interactions, density between the disperse phase and dispersant, particle size and viscosity of the disperse phase.

Several hydrocolloids have been widely used in the food industry, aimed to provide the gel structure, increase viscosity, act as encapsulating agent in formation of films, control crystallization, inhibit syneresis, and increase the physical stability of the products[7]. These hydrophilic polymers can directly influence the properties of foods, such as appearance and texture. Xanthan and chitosan stand out among the widely used hydrocolloids.

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The attributes color and turbidity are decisive for the acceptance of juices and nectars, which should not present sedimentation or phase separation, even with preservation of the nutritional value and taste[6]. Phase separation is associated with chemical interactions, density between the disperse phase and dispersant, particle size and viscosity of the disperse phase. In this context, the aim of this study was to stabilize the guava nectar (Psidium guajava L.) using hydrocolloids and pectinase and evaluate the stability of the bioactive compounds during storage of the nectars.

2. Materials and Methods 2.1 Material About 20 kg of Paluma guavas were obtained from a farm in the municipality of Pelotas, RS, Brazil during the 2013-2014 harvest. Xanthan, guar gum, pectinase enzyme (Sigma–Aldrich) and pregelatinized rice flour, were used as stabilizers. The pectinase enzyme is composed mainly by pectin lyase, polygalacturonase and pectinmethylesterase and small amounts of cellulases and hemicellulases.

The other reagents used in spectrophotometric analyses were of analytical grade.

2.2 Nectar processing Guavas were selected and sanitized in chlorinated water (500 ppm active chlorine), and then the pulp was removed in a machine equipped with 0.8 mm mesh wire. The pulp was packed in polyethylene bags with a capacity of 1 kg and stored at -18 °C until production of nectars. For other

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Krumreich, F. D., Corrêa, A. P. A., Nachtigal, J. C., Buss, G. L., Rutz, J. K., Crizel-Cardozo, M. M., Jansen, C., & Zambiazi, R. C. formulations, stabilizers (xanthan, guar gum, pregelatinized rice flour) and/or pectinase enzyme were added according to Sousa et al.[8] and Rodrigues methodology[9] (Table 1).

The gums were initially dispersed in the sugar and slowly added into the guava pulp to prevent lump formation.

The homogenization was carried out in an industrial blender, followed by a 90 °C/10min heat treatment. After this period the hot filling (85 °C) was carried out in previously sterilized 150 mL glass bottles. The manual closure was performed with metal lids, and was cooled by immersion with water at 45 °C and 25 °C respectively. The bottles were kept at room temperature (22 °C ± 3.6 °C) for 180 days period.

2.3 Physicochemical analysis Analyses of guava nectars were performed soon after processing and at 45 day intervals during 180 days.

All determinations were performed in triplicate, as follows: 2.3.1 pH

and the results were expressed as mg of gallic acid equivalents per 100g sample (wet basis).

2.3.6 Carotenoids Total carotenoids were determined according to AOAC[12] method. Absorbance readings were performed in a spectrophotometer (JENWAY, 6700 UV/Vis) at 470 nm.

A lycopene standard curve was used for quantification of total carotenoids, and the results were expressed as mg of lycopene equivalents per 100g sample (wet basis).

2.3.7 Antioxidant capacity The antioxidant capacity was determined by the ability of the compounds to sequester the radical DPPH (2,2- difenil-1-picrilhidrazila), second method described

by Brand-Williams et al.[13]. Absorbance readings were performed in a spectrophotometer (JENWAY, 6700 UV/Vis) at 517 nm after 24 hours of reaction, and the results were calculated according to Equation 1, expressed as percentage inhibition of DPPH radical.

Determined by potentiometric method (pHmeter Digimed DM 20),using pH 4.0 and 7.0 buffer = solutions. % Inhibition 2.3.2 Titratable acidity Determined by titration the sample with 0.1N sodium hydroxide (NaOH) to pH 8.1. The results were expressed in mg citric acid per 100 g sample (wet basis)[10].

absorbance of control − absorbance of sample ×100 (1) absorbance of control

2.3.8 L-ascorbic acid

Determined by refractive index, using digital refractometer Atago Palette PR-32 α.

Quantified using the titrimetric method of Lorenz‑Steves[14], based on the reducing action of ascorbic acid, using standard iodine and sodium thiosulfate solution and starch as indicator. The results were calculated according to Equation 2, and expressed as mg of L-ascorbic acid per 100g sample (wet basis).

2.3.4 Color

mg ascorbic acid 100mL−1 of juice ( X = )

Measured according to the C.I.E. L* a* b* system, in colorimeter Minolta (CR-300), with illuminant D 65, 8 mm‑illumination area, and L* values (brightness) ranging from black (0) to white (100); a* values from green (-a) to red (+a), and b* values ranging from blue (-b) to yellow (+b).

Where: Y = (total volume of iodine solution X conversion factor) - (volume of thiosulfate solution x conversion factor) Each mL of 0.01 N iodine corresponds to 0.88 mg of ascorbic acid.

2.3.5 Phenolic compounds

2.3.9 Sedimentation

For quantification of total phenolics was used the method described by Swain and Hillis[11], with few modifications.

Absorbance readings were performed in a spectrophotometer (JENWAY, 6700 UV/Vis) at 725 nm. A gallic acid standard curve was used for quantification of the phenolic compounds,

The clarified phase of nectars was analyzed twice a week for 90 days, which corresponds to the stabilization period, and the results were expressed as percentage of stabilized phase (not clarified).

Table 1. Amount of gums and enzymes in the nectars of guava.

The results were expressed as mean and standard deviations concerning the determinations in triplicate.

Data were submitted to Tukey’s and Dunnett test, with 5% significance level, using the SAS statistical software v8.

2.3.3 Total soluble solids

Formulations* (T1) Control** (T2) Xanthan (T3) Guar gum (T4) Pregelatinized rice flour (T5) Enzyme (T6) Enzyme + Xanthan (T7) Enzyme + Guar gum (T8) Enzyme + Pregelatinized rice flour

Amount 0.1% 0.1% 0.1% 1,400 ppm 1,400 ppm + 0.1% 1,400 ppm + 0.1% 1,400 ppm + 0.1%

*The formulations of the nectars were carried out in accordance with Resolution No.12 of 04 September 2003, Art 1 Annex II - Identity Standards and Quality Nectar[5]; **The base formulation (control) of the nectars consists of 55% water, 35% guava pulp and 10% sugar (sucrose).

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[Y × 0,88 mg ] / mL (2)

2.3.10 Statistical analysis

3. Results and Discussion The pH of the nectar formulations containing xanthan (T2), guar gum (T3) and rice flour (T4) did not differ significantly from the control (T1) formulation (4.17 ± 0.01).

Lower pH values were observed for all formulations containing the enzyme, including the formulations with pectinase (T5), pectinase and xanthan (T6), pectinase and guar gum (T7), and pectinase and rice flour (T8). Godoy[15], studied hydrocolloids in guava nectar and found an increase Polímeros, 28(1), 53-60, 2018

Stabilization of guava nectar with hydrocolloids and pectinases in pH value in the control (guava nectar without addition of stabilizer) when xanthan gum was used at various concentrations (0.07, 0.12 and 0.17%). Souza[16] also observed an increase in pH value when xanthan and guar gum were used in peach nectar, when compared to the control. The pH determination is of great importance, since it is a limiting factor for the growth of pathogenic and spoilage bacteria; in addition it defines the heat treatment to be applied, and favors the stability of ascorbic acid, since this vitamin has greater stability at acidic pH[14].

During storage (Figure 1A), a significant increase in pH value was observed for all nectar formulations, except for the nectar containing xanthan gum (T2) and guar gum (T3) at 180 days of storage. These results corroborate the results of several authors, including Silva et al.[17], studying the stability of guava juice packed either in glass bottles or carton, and storing for 250 days at room temperature; Mattietto et al.[18] study with a blend of cajá and umbu nectar packed in glass bottles for 90 days of storage; Leitão[19], study with blackberry nectar packed in glass or polypropylene packages and stored either at room temperature or refrigeration; and Carvalho et al.[20], studying a blended beverage consisting of cashew apple juice and coconut water containing caffeine. According to Silva[21], the increase in pH value during storage may be due to the degradation of ascorbic acid, with respective reduction of free hydrogen ions in the product, which corroborates the findings of this study, once a significant decrease in vitamin C content was observed during storage.

The determination of acidity is another important physicochemical parameter for processing nectars, since it ensures a more pleasant taste and a more vivid color to the products. After processing, all nectars containing the enzyme pectinase (T5, T6, T7 and T8) showed higher total acidity and lower pH values when compared to the control. Essa[22], studied the effects of the addition of an enzyme preparation on plum, banana, and guava juices, and found an average titratable acidity of 0.31% citric acid, which is very close to the value found in our study for the nectars containing the enzyme (0.27% citric acid). However, after the enzymatic treatment, the author found a considerable decrease in viscosity of banana juice. Byaruagaba-Bazirake et al.[23] found no changes in acidity of the pulp after enzymatic treatment. The decrease in pH and increase in acidity of nectar formulations containing the enzyme is expected, since the enzymatic treatment increases the galacturonic acid content in the medium, which is present as pectin chains in the cell walls. An increase in acidity was also observed

by Demir et al.[24] with no changes in pH, probably due to the compounds from carrot juice that may act as a buffer.

Vandresen[25], evaluated enzymatically treated and pasteurized carrot juice, and also found a decrease in pH and an increase in acidity of the pasteurized samples.

In the present study, the titratable acidity remained stable for all formulations during 180 days of storage (Figure 1B), which did not decrease with the increase in pH, particularly at 135 days of storage. There was a slight decrease in acidity of some formulations during the storage time, which was more evident in the formulation containing pectinase and xanthan gum (T6). Pinheiro[26], studied blended cashew apple nectar stored for 30 days, and observed small changes in acidity of nectar packed either in polyethylene terephthalate or glass packages. Similar results were observed by Corrêa[27], who evaluated guava nectar stored at refrigerated (5 ± 2 °C) and room temperature (25 ± 5 °C) for 120 days, and also by Beisman[28] during storage of mango nectar formulations.

The soluble solids content of the guava nectar formulations were significantly higher (14.03 ± 0.12), when compared to the control, except for the formulation with guar gum (T3). The increase in soluble solids was expected, due to the addition of solids in all formulations. The formulation with the pectinase enzyme and rice flour (T8) was the one with the highest amount of soluble solids (16.10 °Brix), and the highest values were observed in the formulations containing pectinases enzymes (T5, T6, T7, T8). These results are probably due to the action of the pectinolytic enzymes that hydrolyze the α (1→4) glycosidic bonds, which increases the soluble solids content in solution. According to Sreenath et al.[29] the enzyme improves the quality of the juice by providing a greater extraction of soluble solids.

This effect was also found by Brasil et al.[30] in extraction and bleaching of guava juice, using 600 ppm of enzyme at 45 °C for 120 minutes, and by Vandresen[25] evaluating enzymatically treated and pasteurized carrot juice.

During storage (Figure 1C), the soluble solids content remained constant for all nectar formulations, which corroborates with the study of Nisida et al.[31] who investigated orange juice packed in aseptic packaging and stored at different temperatures (2 °C, 12 °C and 35 °C), and observed that the concentration of soluble solids remained constant during storage at the three temperatures studied. According to the Ministry of Agriculture, Livestock and Supply, the minimum soluble solids content for guava nectars is 10 °Brix[5]; thus all nectar formulations of this study were within the

Figure 1. Effect of addition of enzymes and the pH hydrocolloid (A), titratable acidity (B) and total soluble solids (C) nectars guava during storage.

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Krumreich, F. D., Corrêa, A. P. A., Nachtigal, J. C., Buss, G. L., Rutz, J. K., Crizel-Cardozo, M. M., Jansen, C., & Zambiazi, R. C. minimum limit defined by the legislation until the end of the storage period.

The color parameters (L*, a* and b*) of all nectar formulations remained very close to the control during the storage periods. However, a significant decrease in L* values was observed for the treatments with xanthan (T2), pectinase (T5), pectinase and xanthan (T6), pectinase and guar gum (T7), and pectinase and rice flour (T8) at the beginning (day 0) and at the end of storage (day 180). When nectar was analyzed individually in relation to the storage time (Figure 2A), L* values significantly increased after 90 days of storage, with subsequent reduction. Sharon et al.[32] studied passion fruit juice, and also found a significant increase in brightness values for 120 days of storage. According to the authors, Maillard reactions may occur, with non-enzymatic browning or even polymerization of phenolic compounds.

Tribst[33] evaluated mango nectar, and also found higher L* values due to the heat treatment to which the product was subjected. Arruda[34], studied the stability of mango nectar packed in polyethylene terephthalate bottles, aluminum cans and cartons, and observed a decrease in L* values during storage due to the oxidation reactions and vitamin C losses.

Both the a* and the b* values show a trend to increasing values for all guava nectars during storage, probably due to the carotenoids content in nectars, since the higher the a* and b* values the closer they are to red and yellow, respectively.

Different nectar formulations showed color values similar to the control. An increase in a* values (Figure 2B) was also observed by Sharon et al.[32] in passion fruit juice during storage. The increase in red color may have been influenced by heating, which causes loss of some components such as carotenoids, sugars, and amino acids, leading to the formation of colored products from the Maillard reaction.

Higher b* values were observed only in some formulations at 90 and 135 days of storage (Figure 2C), when compared to the control. During the 180 day storage, several oscillations were observed in this parameter, with a more significant decrease at 45 days, with no significant differences between the formulations and the control at the end of the study period. The b* values ranged from 1.24 to 4.98, with small increase in yellow color during storage, probably due to the heat treatment applied to nectars, which caused an increase in yellowness. Beisman[28] evaluated the darkening of guava nectar and observed color changes during storage at room temperature, probably due to the rapid degradation of ascorbic acid in the product. This color coordinate plays an important role in guava nectars, since it is directly related to

the carotenoid content in the product, which did not change during storage in all samples analyzed in the present study, thus reflecting in b* values.

Although the carotenoid levels ranged during storage (Figure 3A); lower levels were observed in both the formulations containing xanthan gum (T2) and formulations containing pectinase (T5, T6, T7, T8) at the end of storage, with a small increase in the other samples. Lin & Chen[35], studied the stability of carotenoids in tomato juice heated at 121°C for 40 seconds and stored in the absence and presence of light (10 W) at 4 °C, 25 °C and 35 °C for 12 weeks, and observed losses of 80.1%; 83.5% and 92.1%, respectively, for the samples stored in the absence of light, and 87.4%; 84.9% and 88.3%, respectively, for the samples stored in the presence of light after 90 days of storage. Fernandes et al.[36] investigated hot-packed guava juice stored for 30 days at 28 °C, and found a decrease in lycopene content from 1.51 mg.100g-1 to 1.22 mg.100g-1. Silva et al.[17] also studied guava juice, and found carotenoids content of approximately 1.0 mg lycopene 100g-1, which did not differ within 250 days of storage. The contents reported by those authors are lower than to those found for the guava nectars in our study.

Overall, the samples containing pectinases exhibited higher carotenoids levels when compared to the other samples, both after processing as the end of the storage period.

Phenolic compounds belong to a group of compounds with variable stability, due to their different structures, being directly affected by temperature, light, contact with oxygen, pH, among others. All formulations had very similar content of phenolic compounds after processing in our study (Figure 3B). During storage, a progressive decrease in phenolics was observed for all formulations, except after 90 days of storage. It is observed that unlike the carotenoid content, no differences were observed between the formulations containing or not the enzymes. Paludo and Krüger[37] extracted juice with and without addition of the enzyme pectinase, and also found no significant difference in the phenolic compounds content. Valdés et al.[38] studied guava juice packed in glass packages, and found phenolic compounds content of 26.3 mg of gallic acid equivalents.100g-1, which is lower than the content found in our study. Other guava derived products also presented a decrease in phenolic compounds during storage. Singh & Pal[39] analyzed guava stored under controlled atmosphere for 30 days at 8 °C, and reported a reduction in phenolic compounds from 224.26 mg to 190.56 mg gallic acid equivalents.100g-1. Silva et al.[17] found a reduction from 128.33 mg to 94.98 mg gallic acid equivalents.100g-1 in hot

Figure 2. Influence of the addition of hydrocolloids and enzymes in color parameters L* (A), a* (B) and b* (C) of guava nectars during storage.

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Stabilization of guava nectar with hydrocolloids and pectinases

Figure 3. Influence of the addition of hydrocolloids and enzymes in the carotenoid (A), phenolic compounds (B), L-ascorbic acid (C), antioxidant (D) and sediment (E) nectars guava during storage.

packed guava juice, and from 96.55 mg to 74.38 mg gallic acid equivalents.100g-1 in juice subjected to aseptic processing, from 50 to 250 days of storage at room temperature. In the present study, pasteurization was used in the preparation of guava nectars, which may be associated with the degradation rate of phenolic compounds during storage.

All guava nectars exhibited similar ascorbic acid content throughout storage when compared to the control, except the formulation containing pectinase and rice flour (T8), which showed a lower ascorbic acid content (Figure 3C).

The vitamin C decreased in all guava nectars during storage, and no vitamin C content was found in both the formulations containing pectinase and xanthan gum (T6), and formulation with pectinase and rice flour (T8) after 180 days. Although greater protection on vitamin C was observed in nectars containing gums, the degradation of this vitamin was accelerated in nectars with pectinase. The greatest decrease in vitamin C content was observed from 135 days of storage for all formulations. Leitão[19] found 82.32% degradation of this vitamin in blackberry nectar stored at refrigeration temperature (4 ± 2 °C), and 100% degradation when stored at room temperature for 90 days, evidencing lower degradation of vitamin C at low temperatures. Among all formulations, the nectar with xanthan gum (T2) retained the vitamin C content (15.36 mg.100g-1) within the parameters of the legislation, 14 mg.100g-1[5]. Despite guava is a rich source in this vitamin, it is easily degraded during processing and/or storage due to its instability. Quinteros[40], studied the stability of acerola and carrot nectar, and found a more accelerated loss in the first 90 days of storage, decreasing after this period; unlike the results of the present study, in which vitamin C remained stable at the beginning of storage, with significant degradation at the end of 135 days.

A reduction in vitamin C was also reported by Brito et al.[41] in passion fruit nectar containing coconut water stored at Polímeros, 28(1), 53-60, 2018

room temperature (25 °C), with a loss of 77.87% at the end of 90 days. Similar results were observed by Sousa[8], which reported 38% loss of vitamin C in the nectar containing Ginkgo biloba, Panax Ginseng extracts during 180 days of storage at room temperature (25 °C). Oliva et al.[42] investigated the stability of vitamin C in acerola fruit nectar, and reported losses from 28% to 30% when stored at room temperature at the end of 150 days. The reduction in vitamin C content of nectars during storage can be due to oxidation reactions caused by oxygen inside the package and/or dissolved in the beverage, since nectar was not subjected to deaeration process. The storage temperature and the incidence of light in transparent glass packaging may also have contributed to the reduction of vitamin C levels[43]. According to Fellows[44], pasteurization also causes changes in the nutritional value of food, especially in relation to vitamin C in fruit juices despite being a relatively mild heat treatment. There is a vast literature on the chemical oxidation and/or thermal degradation of vitamin C as a result of bleaching, baking, pasteurization, sterilization, dehydration and freezing[45].

Besides these processing conditions, other factors such as type of packaging, presence of O2, time and temperature of storage, and incidence of light[46] can also contribute to the degradation of vitamin C. Despite significant losses of ascorbic acid were observed in guava nectars up to 180 days of storage, some formulations showed values above the Recommended Daily Intake (RDI) for adults, which is 45 mg daily, until 90 days of storage[47].

Significant differences were observed for the antioxidant activity of guava nectar formulations when compared to the control from 90 to 135 days of storage (Figure 3D). During storage, the different formulations showed variable activity, and all samples containing pectinase (T5, T6, T8), showed a tendency to lower antioxidant activity, except the formulations containing pectinase and guar gum (T7). The decrease of 57/60 57

Krumreich, F. D., Corrêa, A. P. A., Nachtigal, J. C., Buss, G. L., Rutz, J. K., Crizel-Cardozo, M. M., Jansen, C., & Zambiazi, R. C. the antioxidant activity is due to the loss of carotenoids, phenolic compounds, and vitamin C during storage, which was more intense in these formulations when compared to the other formulations, especially in the formulations with pectinase and xanthan gum (T6), and pectinase and flour rice (T8), in which vitamin C was not detected at the end of the storage period. The formulation containing only xanthan gum (T2) showed increased antioxidant capacity during storage, demonstrating its stabilizing potential, not only in the product´s appearance but also the content of bioactive compounds. Leitão[19], evaluated the stability of blackberry nectar, and found a tendency to increase the antioxidant capacity of approximately 9% at both ambient (16 ± 3 °C) and refrigeration (4 ± 2 °C) temperatures. Valdés et al.[38] evaluated guava juice packed in glass packages, and found a 30% inhibition of DPPH radical, which is lower than this study, once the lowest percentage was approximately 33% inhibition at the end of storage period for the formulation containing pectinase and rice flour (T8).

Figure 3E shows phase separation of guava nectars.

The sedimentation occurred more rapidly at the beginning of the process, specifically in the first two weeks of storage, followed by a gradual increase in the height of the precipitate until a stable point was reached. No significant difference was observed for the sample containing xanthan gum (T2) when compared to the control. All the other formulations showed greater stability when compared to the control, especially the formulations containing pectinase (T5, T6, T7, T8), which reached 88%, 80%, 91% and 75% of stabilization, respectively at the end of the storage.

Among the samples containing only gum, the sample with rice flour (T4) showed high stability, demonstrating that the xanthan concentrations used in the present study did not play an important role in stabilizing guava nectars.

Godoy[15], studied the stability of guava nectar during 180 days of storage, and found 99% stability using 0.175% xanthan, which was greater than the amount used in this study. Garruti[48], used 0.2% xanthan gum in passion fruit juice, and found 100% stability for 180 days, while Souza[16] stood out that the addition of 0.2% xanthan gum was one of the best treatments to stabilize peach nectar (94.7%).

The fact of xanthan gum did not produce good results in terms of stabilizing the guava nectars of this study does not corroborate the studies in literature. Vendrúscolo[49] reported that the enzymatic treatment of carambola pulp decreased sedimentation by about 62% when compared to the untreated pulp, probably due to pectin solubilization and release the intercellular juice.

4. Conclusion The quality and physicochemical composition of nectars was affected by the addition of hydrocolloids and/or enzymes, and the addition of enzyme pectinase led to a greater extraction of soluble solids and carotenoids, as well as improved stabilization during phase separation (75% to 91%), especially for the formulation containing pectinase and guar gum. The nectars containing gums, in turn, exhibited higher stability of phenolic compounds and L-ascorbic acid, which directly influenced the higher antioxidant capacity when compared to the formulations 58 58/60

containing pectinases, highlighting the formulation with xanthan gum. According to our results, we conclude that the production of nectar on an industrial scale is a promising alternative, and the use of gums or enzymes can increase carotenoids content and confer protection to phenolic compounds and L-ascorbic acid.

5. Acknowledgements The authors would like to thank CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for funding and support.

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25. Vandresen, S. (2007). Caracterização físico-química e comportamento reológico de sucos de cenoura e laranja e suas misturas (Dissertação de mestrado). Universidade Federal de Santa Catarina, Florianópolis.

26. Pinheiro, A. M. (2008). Desenvolvimento de néctares mistos à base de caju (Anacardium occidentale L) e açaí (Euterpe oleracea mart.). (Dissertação de mestrado). Universidade Federal do Ceará, Fortaleza.

27. Corrêa, M. I. C. (2002). Processamento de néctar de goiaba (Psidium guajava L. var. Paluma): compostos voláteis, características físicas e químicas e qualidade sensorial (Dissertação de mestrado). Universidade Federal de Viçosa, Viçosa.

28. Beisman, R. B. (2000). Processamento e avaliação da qualidade do néctar e néctar light de dois cultivares de pêssego adaptados ao clima subtropical (Dissertação de mestrado). Escola Superior de Agricultura “Luiz de Queiroz”, Universidade de São Paulo, Piracicaba.

29. Sreenath, H. K., Sudarshanakrishana, K. R., & Santhanam, K. (1994). Improvement of juice recovery from pineapple pulp/residue using celulases and pectinases. Journal of Polímeros, 28(1), 53-60, 2018

Fermentation and Bioengineering, 78(6), 486-488. http:// dx.doi.org/10.1016/0922-338X(94)90054-X. 30. Brasil, I. M., Maia, G. A., & Figueiredo, R. W. (1995).

Physical-chemical changes during extraction and clarifi cation of guava juice. Food Chemistry, 54(4), 383-386. http://dx.doi. org/10.1016/0308-8146(95)00066-R. 31. Nisida, A. L. A. C., Menezes, H. C., & Tocchini, R. P. (2002).

Estabilidade de suco de laranja (Citrus Sinensis) refrigerado, acondicionado em embalagem asséptica. Brazilian Journal of Food Technology, 5, 95-100.

32. Sharon, E. S., Dantas, S. T., Menezes, H. C., Soares, B. M. C., & Nunes, M. F. (2007). Estabilidade sensorial de suco de maracujá pronto para beber acondicionado em latas de aço.

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33. Tribst, A. A. L. (2008). Efeito do processamento por alta pressão dinâmica combinado com tratamento térmico brando na inativação de Aspergillus niger em néctar de manga (Dissertação de mestrado). Universidade Estadual de Campinas, Campinas.

34. Arruda, A. F. (2003). Estudo da estabilidade do néctar de manga (Mandifera indica L.) envasado em garrafa PET, comparado com envasados em embalagem cartonada e lata de alumínio (Dissertação de mestrado). Universidade Estadual de Campinas, Campinas.

35. Lin, C. H., & Chen, B. H. (2005). Stability of carotenoids in tomato juice during storage. Food Chemistry, 90(4), 837-846. http://dx.doi.org/10.1016/j.foodchem.2004.05.031.

36. Fernandes, A. G., Maia, G. A., Sousa, P. H. M.., Costa, J. M. C., Figueiredo, R. W., & Prado, G. M. (2007). Comparação dos teores em vitamina C, carotenóides totais e fenólicos totais do suco tropical de goiaba nas diferentes etapas de produção e influencia da armazenagem. Alimentos e Nutrição., 18, 431438.

37. Paludo, M. C., & Krüger, R. L. (2011). Ação da enzima pectinase na extração do suco de jabuticaba. Arquivos de Ciência da Saúde UNIPAR., 15, 279-286.

38. Valdés, S. T., Vaz Tostes, M. G., Della Lucia, C. M., Hamacek, F. R., & Pinheiro-Sant’ana, H. M. (2012). Ácido ascórbico, carotenoides, fenólicos totais e atividade antioxidante em sucos industrializados e comercializados em diferentes embalagens.

Revista do Instituto Adolfo Lutz, 71(4), 662-669.

39. Singh, S. P., & Pal, R. K. (2008). Controlled atmosphere storage of guava (Psidium guajava L.) fruit. Postharvest Biology and Technology, 47(3), 296-306. http://dx.doi.org/10.1016/j. postharvbio.2007.08.009.

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Universidade Estadual de Campinas, Campinas.

41. Brito, I. P., Faro, Z. P., & Melo, S. C., Fo. (2004). Néctar de maracujá elaborado com água de coco seco (Cocos nucifera, L.).

In Congresso Brasileiro de Ciência e Tecnologia de Alimentos (p. 9). Recife: Sociedade Brasileira de Ciência e Tecnologia de Alimentos.

42. Oliva, P. B., Menezes, H. C., & Ferreira, V. L. P. (1996). Estudo da estabilidade do néctar de acerola. Ciência e Tecnologia de Alimentos., 16, 228-232.

43. Carvalho, J. M., Maia, G. A., Figueiredo, R. W., Brito, E. S., & Garruti, D. S. (2005). Bebida mista com propriedade estimulante à base de água de coco e suco de caju clarificado.

Ciência e Tecnologia de Alimentos., 25(4), 813-818. http:// dx.doi.org/10.1590/S0101-20612005000400030.

44. Fellows, P. (1997). Food processing technology: principles and practice. Abington: Woodhead. 505 p.

45. Burdurlu, H. S., Koca, N., & Karadeniz, F. (2006). Degradation of vitamin C in citrus juice concentrates during storage.

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Krumreich, F. D., Corrêa, A. P. A., Nachtigal, J. C., Buss, G. L., Rutz, J. K., Crizel-Cardozo, M. M., Jansen, C., & Zambiazi, R. C. Journal of Food Engineering, 74(2), 211-216. http://dx.doi. org/10.1016/j.jfoodeng.2005.03.026.

46. Correa-Neto, R. S., & Faria, J. A. F. (1999). Fatores que influem na qualidade do suco de laranja. Ciência e Tecnologia de Alimentos., 19(1), 153-160. http://dx.doi.org/10.1590/ S0101-20611999000100028.

47. Resolução RDC nº 269, de 22 de setembro de 2005. (2005, 23 de setembro). Aprova o regulamento técnico sobre a Ingestão Diária Recomendada (IDR) de proteína, vitaminas e minerais. Diário Oficial da República Federativa do Brasil, Brasília.

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48. Garruti, D. S. (1989). Contribuição ao estudo da estabilização física do suco de maracujá integral (Passiflora edulis F. flavicarpa Deg) (Tese de doutorado). Universidade Estadual de Campinas, Campinas.

49. Vendrúscolo, A. T. (2005). Comportamento reológico e estabilidade física de polpa de carambola (Averrhoa carambola L.) (Dissertação de mestrado). Universidade Federal de Santa Catarina, Florianópolis.

Received: May 20, 2016 Revised: Mar. 15, 2017 Accepted: May 12, 2017

Polímeros, 28(1), 53-60, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.01417

Cashew nut shell liquid, a valuable raw material for generating semiconductive polyaniline nanofibers Raiane Valenti Gonçalves1, Mara Lise Zanini1, José Antonio Malmonge2, Leila Bonnaud3 and Nara Regina de Souza Basso1* Faculdade de Química, Pontifícia Universidade Católica do Rio Grande do Sul – PUCRS, Porto Alegre, RS, Brazil 2 Universidade Estadual Paulista – UNESP, Faculdade de Engenharia, Ilha Solteira, SP, Brazil 3 Laboratory of Polymeric and Composite Materials, Materia Nova Research Center, Mons, Belgium 1

*nrbass@pucrs.br

Abstract Cashew nut shell liquid (CNSL) is an abundant and renewable by-product of the cashew nut industry. It appears to be a valuable raw material for generating semiconductive polyaniline (PAni) nanomaterial with enhanced thermal stability and well-defined nanofiber morphology following a polymerization dispersion process. This study confirms that CNSL acts as a soft template during PAni synthesis, leading to an improvement in the nanofiber aspect. CNSL also improves the thermal stability of the PAni nanomaterial. Moreover, CNSL is an effective surfactant that promotes and stabilizes the dispersion of PAni nanofibers within water, allowing the more ecofriendly preparation of PAni nanomaterial by substituting the commonly used organic solvent with aqueous media. Finally, although CNSL promotes the formation of the conductive emeraldine salt form of PAni, increasing CNSL concentrations appear to plasticize the PAni polymer, leading to reduced electrical conductivity. However, this reduction is not detrimental, and PAni nanofibers remain semiconductive even under high CNSL concentrations.

Keywords: cashew nut shell liquid, nanofibers, polyaniline, semiconductive material, soft template.

1. Introduction Polyaniline (PAni) in the emeraldine salt form is one of the most widely studied conducting polymers because of its easy synthesis, low cost, and acid-doping/dedoping chemistry-based property. Furthermore, the final polymer shows high stability and excellent electrical properties when exposed at environmental conditions. A limitation of PAni in the emeraldine salt form is its insolubility in common organic solvents and polymers, which limits its application as a filler in nanocomposites. Many studies have tried to overcome this difficulty[1,2].

PAni nanostructures can be synthesized with zero dimensions (e.g., nanospheres[3]), one dimension (e.g., nanofibers[4], nanorods[5], and nanotubes[6]), and two dimensions (e.g., nanobelts[7] and nanosheets[8]). PAni nanostructures have been widely investigated because they combine the unique characteristics of a conventional polymer with the quantum effects of nanomaterials[9,10]. Different experimental parameters such as type of dopant used, [aniline]/[soft template] ratio, pH, temperature, and reaction time can strongly affect the PAni morphology[1,11-13].

PAni nanofibers are prepared by methods such as using soft templates[4,14] and surfactant-free emulsion polymerization[15]. Micelle as a soft template has been regarded as an appropriate theory in order to describe the formation of the PAni nanostructure[16-18]. In this model the dopant with an amphiphilic structure form ordered templates like micelles and bi-layers to act as seeds for the growth of polyaniline chains and therefore the morphology of the final

Polímeros, 28(1), 61-68, 2018

product is highly dependent on the structure of the dopant molecule and its ability to form stable micelles in water.

The high surface area of PAni nanofibers allows potential applications in nanodevice manufacturing and preparation of polymeric conductive composites. Therefore, different mechanisms and methodologies for synthesizing PAni nanofibers have been studied[4,19,20].

The use of different soft template in the PAni synthesis has been reported in literature. Yin and Yang used dodecylbenzene sulfonic acid (DBSA) as a soft template in the synthesis of polyaniline doped with hydrochloric acid (HCl). It was observed that the morphology and electrical conductivity of the resulting PAni depend on the ratio [aniline]: [DBSA] and HCl concentration. PAni nanofibers and nanotubes with electrical conductivity values of 0.16 S.cm-1 and 5.3 × 10-3 S.cm-1, respectively, were obtained in the presence of low DBSA and HCl concentrations[11]. Sucrose octaacetate as a soft template was also used in the synthesis of PAni doped with HCl. PAni synthesized with different sucrose octaacetate contents showed electrical conductivity values in the order of 10-1 S.cm-1, which are comparable to other conventional methods described in literature. The morphology of nanofibers or nanorods was influenced by the sucrose content and agglomerates were observed increasing the amount of the soft template[21].

In another work PAni was synthesized using HCl as dopant and the N-cetyl-N, N, N-trimethyl trimethylammonium bromide (CTAB) surfactant as soft template. The authors found that surfactant/oxidant ratio influenced the aniline polymerization and different morphologies and electrical

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O O O O O O O O O O O O O O O O

Gonçalves, R. V., Zanini, M. L., Malmonge, J. A., Bonnaud, L., & Basso, N. R. S. conductivity values were obtained for PAni: nanotube, nanorod, nanosphere and nanosheet with electrical conductivity of 0.92; 0.30; 0.0009 and 0.025 mS.cm-1, respectively[22].

Cashew nut shell liquid (CNSL), a by-product of the cashew industry, is rich in natural nonisoprenoid phenolic lipids. It contains four major components with long unsaturated side chains of fifteen carbons: anacardic acid, cardanol, 2-methylcardol, and cardol, as shown in Figure 1[23,24].

The final composition of CNSL depends on the oil extraction method. Natural CNSL mainly contains anacardic acid and is obtained from cold extraction. In hot extraction, anacardic acid is converted to cardanol with 90 wt% yield, giving so-called technical CNSL. The use of these natural phenolic compounds for the synthesis of epoxy, alkyd, and phenolic resins, miscellaneous coating materials, adhesives, and modifying agents for resins and plastics have been reported[25,26]. In addition, the authors reported that CNSL can act as a secondary dopant and plasticizer in the synthesis of PAni blends[27,28].

The influence of CNSL on the mechanical and electrical properties of PAni.DBSA and styrene butadiene styrene tri-block copolymer (SBS) blends was evaluated. Results showed that the CNSL improved the mechanical and electrical properties due to the formation of cocontinuous‑type morphology on the blend and a secondary doping process on DBSA-doped polyaniline[26]. Other researchers evaluated the action of the CNSL derivative, known as cardanol, functionalized with butane sulfonic acid, on the PAni synthesis. The functionalized cardanol acted as a dopant in the synthesis and promoted the formation of different nanostructures with electrical conductivities in the range of 10-1 S.cm-1[27]. In a previous work, cardanol was used as a primary dopant for PAni, producing a polymer with electrical conductivity of 9.7 × 10-1 S.cm-1. The presence of cardanol promoted the formation of PAni nanofibers mixed with particulates[29].

Although studies indicate that CNSL can potentially improve the properties of PAni blends, the action of CNSL in the polymerization of aniline and its influence on the properties of the PAni thus obtained have not yet been investigated in detail. This study investigates the influence of technical CNSL on the morphology, solubility, and electrical and thermal properties of PAni synthesized by dispersion polymerization.

2. Materials and Methods 2.1 Materials Aniline (analytical grade from Synth) was purified by distillation before polymerization. Hydrochloric acid (HCl) (analytical grade from Neon), ammonium persulfate (APS)

(ACS reagent from Sigma-Aldrich), and cashew nut shell liquid (technical CNSL from Vernisul, Brazil) were used without further purification.

2.2 Synthesis of doped polyaniline The doped PAni was synthesized in the absence and presence of CNSL by dispersion polymerization using HCl as a dopant and APS as an oxidant, according to the literature[19].

The [HCl]/[aniline] ratio was fixed at 3.3. HCl 37 wt% (71.2 mmol) and freshly distilled aniline (21.48 mmol) were dispersed in 200 mL of distilled water. Then, APS (33.96 mmol) was added to the solution. The reaction occurred at 25 °C with continuous stirring for 60 min.

The dark green product was filtered and washed with ethanol to remove oligomers and dried for 48 h in a dessicator.

By using the same methodology, a different amount of CNSL (25 and 40 wt% relative to the weight of aniline) was added to the mixture. The effects of experimental parameters such as the reaction time (30, 60, and 120 min) and temperature (0 °C, 25 °C, and 55 °C) were also investigated.

2.3 Characterization Field-emission scanning electron microscopy (FESEM) was performed using an Inspect F50 microscope. The samples in powder form were metalized with gold. Transmission electron microscopy (TEM) was performed on a Tecnai GM2100F microscope with operating voltage of 80 kV. The electrical conductivity was determined by the four‑point probe method (Keithley Instruments, model 236, and Multimeter HP34401) on pellet prepared by compacting the PAni powder. The absorption spectra of KBr pellets in the infrared region were obtained using a Perkin Elmer Spectrum One Fourier transform infrared spectrometer (FT‑IR). UV‑visible spectrometry (UV-vis) measurements were performed between 200 and 1100 nm using an HP Hewlett Packard 8453. Tests were conducted by preparing a PAni/ethanol solution for each sample. Thermogravimetric analysis (TGA) was performed using the TA Instruments Q60 under nitrogen atmosphere from 30 °C to 800 °C at a heating rate of 20°C/min. The crystallinity of the powdered form was measured using a Shimadzu 7000 X-ray diffractometer with Cu Kα radiation (λ = 0.1540 Å) at room temperature.

To evaluate the influence of CNSL on the solubility of PAni in water, the methodology described in the literature was adopted[15]. Doped PAni (30 mg) was added to 30 mL of distilled water and ultrasonicated for 30 min at room temperature. Undissolved PAni was separated by filtration, dried at 100 °C in an oven for 1 h, and finally weighed.

Figure 1. Major components of CNSL. 62 62/68

Polímeros, 28(1), 61-68, 2018

Cashew nut shell liquid, a valuable raw material for generating semiconductive polyaniline nanofibers

3. Results and Discussions 3.1 Influence of CNSL concentration The FT-IR spectrum of doped PAni (Figure 2) shows structural characteristics consistent with those of previous reports. The peak at ~2915 cm-1 was attributed to the aliphatic C-H stretching of CNSL[28]. The peaks at 1568 and 1487 cm-1 were attributed with the C=C stretching modes of the quinoid and benzenoid units, respectively. The peak at 1294 cm-1 was attributed to the C-N deformation of the benzenoid unit.

The peak at 1118 cm-1 was attributed to the C-H bending vibration of the N=Q=N segment[30,31]. The ratio between the intensity of the peaks at 1568 cm-1 (quinoid ring stretching–Q) and 1487 cm-1 (benzenoid ring stretching–B) was used to compare the doping efficiency between the samples[32].

According to the FT-IR spectra of the prepared samples, the ratio [I1487cm-1]/[I1568cm-1] is close to 1, confirming that the doped conductive PAni was in the emeraldine salt form.

Figure 3 shows the UV-Vis spectrum of the investigated samples. The entire spectra showed two bands at 340 - 370 nm and 400 - 440 nm and over 700 nm. The first band was attributed to the π-π* electron transition of the benzenoid ring while the second and third bands correspond to the polaron π* transition and π-polaron transition[31,33].

Usually the first two bands are often combined into a flat or distorted single peak with a local maximum between the two peaks[34,35]. The intensity of the polaron bands absorption decreased with the introduction of the higher amount of CNSL. This phenomenon is related to the doping effectiveness of the polymer backbone[34]. The ratio between the polaron band absorbance (790-850 nm) and benzenoid π-π* electron transition (340-370 nm) roughly estimate the level of PAni doping[34,36]. The values that were found were 0.91, 0.90 and 0.76 for 0% CNSL, 25% CNSL and 40% CNSL, respectively. The sample with 40% CNSL shows the lowest level of doping and therefore is expected to have lower electrical conductivity.

The influence of CNSL on the morphology of PAni can be evaluated from FESEM micrographs. Figure 4 shows that PAni produced without CNSL showed a morphology predominantly formed by agglomerates, whereas an increase in the CNSL concentration favored the formation of nanofibers.

The agglomerated morphology of synthesized PAni without

Figure 2. FT-IR spectrum of PAni nanofibers synthesized without and with CNSL. Polímeros, 28(1), 61-68, 2018

the addition of CNSL can be explained by the formation of unstable micelles of the dopant-aniline complex in water.

The addition of CNSL can lead to an acid-base interaction between the CNSL and aniline salts in an aqueous medium reaction to form stable cylindrical micelles[27]. Therefore, CNSL, acts as a soft template and promotes the formation of PAni nanofibers with controlled dimensions through a self-assembly process[22].

Figure 5 shows a TEM image of the PAni synthetized with 25% CNSL. TEM image of PAni synthetized with 25% CNSL shows dispersed and interconnected fibers with an average diameter of (66 ± 12) nm and average length of (1053 ± 128) nm, resulting in an aspect ratio of (18 ± 6) nm.

Table 1 shows electrical conductivity values of PAni synthetized with and without CNSL. The conductivity values are of the same magnitude of those found in literature[11,21,22].

With the addition of CNSL, the electrical properties of PAni degrade yet not in a detrimental manner. This result is no surprise and can be explained by the chemical structure of CNSL. Specifically the CNSL has a long aliphatic side chain attached to an aromatic ring. Compounds with long side chains can act as plasticizers, increasing the spacing between polymer chains, thus decreasing in crystallinity and increasing solubility. An increase in the spacing between the polymer chains reduces the mobility of charge carriers[12]. In addition the insertion of CNSL also affects the doping efficiency of polyaniline as shown in Figure 3. These associated effects result in a decrease in electrical conductivity mainly for the sample containing 40% of CNSL. The XRD scan in Figure 6 shows that the PAni prepared without CNSL exhibits four characteristic diffraction peaks

Figure 3. UV-vis absorption spectrum of PAni with and without CNSL. (a) 0% CNSL; (b) 25% CNSL, and (c) 40% CNSL. 63/68 63

Gonçalves, R. V., Zanini, M. L., Malmonge, J. A., Bonnaud, L., & Basso, N. R. S.

Figure 4. FESEM micrographs of synthetized PAni with (A) 0% CNSL, (B) 25% CNSL, and (C) 40% CNSL. Table 1. Solubility, electrical, and thermal (as obtained by TGA) properties and XRD data of PAni synthetized without and with CNSL.

Figure 5. TEM micrograph of synthesized PAni with 25% CNSL.

Figure 6. X-ray diffraction patterns of PAni nanofibers synthesized without and with CNSL.

with distinct intensities located at 2θ ≅ 6°, 15°, 19° and 25° as described in literature[37-40]. The peaks located at 2θ ≅ 6° and 15° disappear with the addition of CNSL, indicating a lower organization of the polymeric chain[40]. The ratio between the intensities of the peaks at 25° and 19°, [I25°]:[I19°]¸ 64 64/68

CNSL (%)

Electrical Conductivity (S.cm-1)

Tonset (°C)

Tmax (°C)

0 25 40

2.6 × 100 8.1 × 10-1 2.3 × 10-3

327 350 352

408 443 447

Solubility of PAni [I25°]:[I19°] in water (%) 6 8 2 94 1 97

indicates the crystallinity of PAni; the higher the value of this ratio the better the ordering in the crystal structure[22].

Table 1 shows the ratios [I25°]:[I19°] of the prepared samples.

Higher crystallinity was observed in polymers prepared without the addition of CNSL. This is because CNSL can plasticize PAni, and thus, PAni nanofibers containing the highest amount of CNSL show lower crystallinity. These results are consistent with the electrical conductivity results.

As discussed, lower crystallinity results in lower electrical conductivity[41].

The main disadvantages of conductive PAni in the emeraldine salt form are insolubility in water and conventional organic solvents and incompatibility with many conventional polymers owing to high aromaticity[32]. The solubility of the prepared PAni samples was evaluated, and the results are shown in Table 1 and Figure 7. Table 1 indicates that the presence of CNSL increased the solubility of PAni in water. The size of the CNSL side chains promotes interchain separation, facilitating the penetration of solvents molecules in clusters of polymer chains[12].

Figure 8 shows TGA curves of the PAni nanofibers synthesized with different CNSL concentrations. PAni shows four stages of weight loss, independent of the experimental conditions. The initial weight loss between 50 °C and 100 °C can be attributed to the evaporation of water molecules. The second stage between 100 °C and 250 °C is due to free HCl (dopant unbound) and removal of low-molecular‑weight oligomers[30,42]. The third stage between 250 °C and 300 °C is attributed to loss of the primary dopant HCl[30,42-44]. The final stage between 300°C and 700°C is attributable to the degradation of the polymer[30,44-46]. PAni is completely oxidized at ~700 °C[30,46]. Table 1 shows that increasing the amount of CNSL in PAni nanofibers leads to an increase in the initial degradation temperature (Tonset) and maximum mass loss rate temperature (Tmax) relative to Polímeros, 28(1), 61-68, 2018

Cashew nut shell liquid, a valuable raw material for generating semiconductive polyaniline nanofibers those of pure PAni. Tonset and Tmax increase by ~25 °C and ~40 °C, respectively, when using 25% CNSL and 40% CNSL. These results indicate that CNSL significantly improved the thermal stability of PAni nanofibers.

Figure 7. Solubility of different samples of PAni in water: (A) 0% CNSL, (B) 25% CNSL, and (C) 40% CNSL.

3.2 Influence of reaction time and temperature The morphology and electrical properties of PAni are strongly influenced by the experimental conditions. Therefore, the influence of temperature and reaction time on the properties of PAni nanofibers was evaluated[47,48]. As described above, adding 25% CNSL improved the nanofiber morphology and thermal properties, and therefore, this experimental condition was fixed so as to evaluate the other parameters. Table 2 shows the evaluated parameters and results. To evaluate the influence of reaction time on the morphology and electrical properties of PAni nanofibers, small and large reaction time of 30 and 120 min, respectively, were evaluated. In all cases, FTIR and UV-vis spectra (not presented here) confirmed the generation of PAni in its conductive emeraldine salt form.

Figure 9(a) and Table 2 indicate that PAni synthesized with a shorter reaction time of 30 min showed good-quality fibers but with low electrical conductivity of 8.7×10-4 S.cm-1.

This is because the reaction time was not sufficient for fully doping the polymer, leading to a low degree of protonation.

On the other hand, Figure 9(b) and Table 2 indicate that a longer reaction time of 120 min favored the formation of agglomerates and reduced electrical conductivity. This is because of secondary growth during polymerization.

The longer the reaction time, the higher is the probability of the PAni polymeric chain becoming a support for the growth of irregular structures[49]. As shown in Figure 4(b) and Table 2, a reaction time of 60 min is sufficient to Table 2. Electrical conductivity under different experimental conditions.

Figure 8. TGA plots of PAni samples.

Reaction time

Temperature

(min)

(°C)

Average diameter (nm)

30 60 120 60 60

25 25 25 0 55

64 ± 11 66 ± 12 74 ± 15 85 ± 14 68 ± 13

Electrical conductivity (S.cm-1) 8.7 × 10-4 8.1 × 10-2 1.3 × 10-4 1.1 × 10-4 1.0 × 10-3

Figure 9. FESEM micrographs with reaction time of (A) 30 min and (B) 120 min.

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Gonçalves, R. V., Zanini, M. L., Malmonge, J. A., Bonnaud, L., & Basso, N. R. S.

Figure 10. FESEM micrographs of PAni synthesized at temperature of (A) 0° C and (B) 55 °C.

produce conductive polymer nanofibers with well-defined morphology.

Polymerization was performed at three different temperatures: 0 °C, 25 °C, and 55 °C. FESEM images showed the presence of aggregates of PAni nanofibers for reactions at temperatures of 0°C and 55°C (Figure 10(a) and (b), respectively), whereas the reaction at 25°C generated high‑quality nanofibers (Figure 4(b)). The electrical conductivity was also sensitive to temperature. The sample prepared at 25°C showed electrical conductivity that was 100 and 10 times higher than that of samples synthesized at 0°C and 55°C, respectively, as shown in Table 2.

4. Conclusions Adding CNSL during the synthesis of PAni promoted the formation of nanofibers and increased the thermal stability. Moreover, CNSL appears to be an effective surfactant that promotes and stabilizes the dispersion of PAni nanofibers in water, allowing ecofriendly synthesis.

The presence of CNSL promotes the plasticization of PAni nanofibers, thus degrading the electrical properties.

Nevertheless, PAni nanofibers remain semiconductive even at high CNSL concentrations (i.e., 40%). Nanofibers with the best conductivity and most well-defined morphology were obtained when the reaction occurred at 25 °C for 60 min. Reaction times of 30 or 120 min and temperatures of 0 °C or 55 °C resulted in the formation of agglomerates and reduced the electrical conductivity. These results clearly indicate that the lateral aliphatic chain allows CNSL to act as a soft template, thus improving the PAni morphology and increasing the surface area of the polymer. Thus, CNSL, a biodegradable and renewable resource, can potentially expand the technological applications of PAni nanofibers.

5. Acknowledgements This work was support by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e 66 66/68

Tecnológico (CNPq). The authors acknowledge VERNISUL by supply of the technical CNSL.

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Received: Mar. 13, 2017 Revised: May 11, 2017 Accepted: May 12, 2017

Polímeros, 28(1), 61-68, 2018

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.07916

Reinforcement of poly (vinyl alcohol) films with alpha-chitin nanowhiskers Hugo Lisboa1* 1

Unidade Acadêmica Engenharia de Alimentos, Universidade Federal de Campina Grande – UFCG, Campina Grande, PB, Brazil *hugom.lisboa80@gmail.com

Abstract Composites Films were produced using Poly (Vinyl Alcohol) as the soft material and reinforced with Chitin Nanowhiskers(NWCH) as the rigid material. The present work studies the reinforcing mechanisms of NWCH in PVA films, made through a solvent casting technique and characterized for their calorimetric, swelling and mechanical properties. DSC tests revealed a sharp increase of 45 °C in glass transition temperatures with only 1.5% NWCH, while melting temperature had a small increases suggesting an anti-plasticizing effect. Swelling tests revealed decreasing hygoscopy when NWCH volume fraction increases. Estimates for elastic tensile modulus using a model that predicts the formation of a percolating network were not consistent with the experimental data of tensile tests suggesting that contrary to the reinforcement with cellulose nanowhiskers the percolating network is not primarily responsible for the reinforcement of the films. By adjusting the Halpin-Tsai equations, modified by Nielsen it was found that the mechanical properties were mainly influenced by the packing of the NWCH. Keywords: Chitin, Nanocomposites, PVA, Nanowhiskers, Reinforcement.

1. Introduction The dependence of non-biodegradable petroleum derived polymers such as polyethylene, polypropylene, terephtahlate (PET), poly styrene, etc can cause serious threats to the environment if alternatives aren’t researched.

Biodegradable polymers often show low chemical and physical properties when compared to the their counterpart[1,2].

One example of such polymers is Poly (Vinyl alcohol), PVA, which is a semi-crystalline thermoplastic produced from the deacetylation reaction of poly(vinyl acetate) and composed of large number of hydroxyl groups making it an hydrophilic polymer and totally soluble in water. It can be easily processed into thin films, and provides a good chemical resistance[3]. However, these properties occur only in the dry state, since this polymer is very hydrophilic and the water absorption decreases considerably their properties, even to dissolve it again. This feature substantially limits its field of application, requiring crosslinking usually with toxic chemicals[4].

Chitin is the second most abundant polysaccharide in nature, followed by cellulose, and its main source of commercial extraction are the shells of crustaceans[5].

This feedstock is an underutilized abundant solid waste from food industry, with a negative environmental impact that stems largely from shrimp processing industry using aquaculture as the main provider[6]. Novel materials from these sources are being considered eco-friendly due their biodegradability and because their use lessens or avoids petrochemical derivatives. It is considered that natural additives such as chitin nanowhiskers represents a major investment for environment preservation, being also interesting in industrial terms, if a composite have better behavior in water uptake or mechanical properties than the

Polímeros, 28(1), 69-75, 2018

polymer itself[7]. The inclusion of nanowhiskers in different polymer matrixes, both synthetic and natural, proved to be advantageous in the strengthening of mechanical properties, water absorption and thermal stability. The mechanical properties enhancement is due to the interface created between polymer and nanowhiskers and interactions between nanowhiskers themselves[8]. Several studies with similar results performed for different systems, explain that for a specific amount of nanowhiskers, a percolation phenomena occurs leading to extensive hydrogen bonding between nanowhiskers thus increasing the composite mechanical properties[9-14]. The term percolation was first introduced by Hammersley in 1957[15], and refers to a statistical geometric model. This model can be applied to any system where it is expected to have a possibility of connection between constituents. Studies about cellulosic nanowhiskers have proven that the material reaches the percolation above a critical volume fraction[16]. This percolation threshold is the difference between the connection of a finite number of elements and a connection to an infinite number of elements[17]. The factors influencing this limit, are the aspect ratio of nanowhiskers, the possibility of occurrence of interactions between particles and their orientation.

When applied to cellulosic nanowhiskers, this model allows describing the unusual increase on mechanical properties, since presupposes the formation of a rigid network between nanowhiskers. Presentlty it is still unclear weither this model is also valid for chitin nanowhiskers. Sriupayo and colleagues mechanically reinforced PVA films with chitin nanowhiskers but the mechanism of such reinforcement was not clarified[18]. In another work Roohani et al, reinforced PVA films with cellulose nanowhiskers but the percolation

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O O O O O O O O O O O O O O O O

Lisboa, H. model did not successfully fitted the experimental data[19].

Uddin and co-workers introduced highly oriented chitin nanowhiskers into PVA films resulting in a high increase of mechanical properties but when applying a rule of mixtures could not explained the reinforcement mechanism[20]. A recent work from Sonker et al, introduced cellulose nanowhiskers into crosslinked PVA films discovering a synergistic effect between the crosslinks and the nanowhiskers in tensile studies due to decreased chain mobility[21].

PVA / nanowhiskers composites are biodegradable and environmentally friendly materials which means its utilization is more beneficial to the environment than the use of non-degradable plastics[22]. Several works proved that the composites produced by inclusion of nanowhiskers elements in PVA may be useful for many applications in different sectors like food packaging, agriculture, chemical engineering and in medical field.that require some sort of barrier. Packaging materials require good barrier and mechanical properites which can be introduced by the nanowhiskers[23]. Mulching methodology in agriculture can also benefit from plastics with increased barrier properties and the films biodegradability[24,25]. PVA / nanocellulose hydrogels can be used as super-absorbents to deal with water pollution problems due to oils spills or chemical spilage[26]. In the medical field, PVA films could be used as wound dressings[10,27] and be doped with silver nanocrystals to increase bacterial resistance while protecting skin wounds[28] In all these cases, features such as chemical and mechanical resistance are decisive for the behavior of separation membranes.

The aim of the present work is to study PVA films reinforced with nanowhsykers of chitin, improving the calorimetric and mechanical properties PVA films.

Additionaly, while for cellulose nanowhiskers its clear that the mechanical reinfocerment is trough a percolation mechanism, the mechanism behind the reinforcement with chitin nanowhiskers is not yet understood, so the intent of the present work is to clarify such mechanism using two different models.

2. Materials and Methods 2.1 Production of chitin nanowhiskers (NWCH) Pandalus borealis shrimp shells were obtained from Aquamaris, João Pessoa, Brazil. Purified chitin was extracted adapting a previous reported procedure[29]. Briefly, frozen shrimp shells were firstly dried and grounded. Desmineralization step was performed using 1M aqueous solution of hydrochloric acid (Sigma-Aldrich, Reagent Grade), at room temperature for 1h then filtered and washed until neutral pH. Deproteinization was performed using 1M aqueous solution of Sodium Hydroxyde (Sigma-Aldrich, reagent grade) at 80 °C for 1h then filtered and washed until neutral pH. hydrolyzed with 3N hydrochloric acid for 1.5h at boiling temperature.

The suspensions were then diluted with distilled water until pH was superior to 2. Above this pH the supernatant was stored for dialysis against water for complete neutralization.

The neutralized suspensions were then freeze-dried, and dried chitin nanowhiskers were obtained.

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2.2 Preparation of nanocomposite films 2.0 wt% PVA (ACROS, 95% hydrolysed, Mw = 95000) aqueous solutions were prepared by dissolving in water at boiling temperature for 1h and then stored overnight. Nanocomposite films were produced using different amounts of dried chitin nanowhiskers mixed with PVA solution, and subjected to 1 minute of sonication for complete homogeneization.

The prepared solutions with 0, 1.5, 3.0, 5.6 and 10.0% of volume fraction (vf) of NWCH were cast with the aid of a calibrated ruler on a Teflon surface, and left to dry at laboratory atmosphere.

2.3 Characterization Transmission electron microscopy (TEM) observations were made with a Hitachi H8100 electron microscope with an accelerating voltage of 100kV. A droplet of a dilute suspension (0.02 wt%) of chitin nanowhiskers was deposited onto carbon-coated grid and allowed to dry. No stain agent was used.

Infrared Spectroscopy (FTIR) Measurements were performed using a Spectrum 400, FT-IR/ FT-NIR Spectrometer Perkin Elmer. KBr discs were made by mixing 1mg of dried NWCH with 100mg of KBr. Differential scanning calorimetry (DSC) was performed using a NETZSCH DSC 204F1 Phoenix. Each sample was heated from 25 to 250 °C at a heating rate of 10 °C/min.

The melting temperature (Tm) was taken as the peak temperature of endotherm curve while the glass transition temperature (Tg) was taken as the inflection point of the specific heat increment at the glass-rubber transition.

To determine the swelling index, PVA films with increasing NWCH concentrations were cut into 2.0 cm × 2.0 cm pieces and immersed in distilled water for small time intervals were swollen samples were taken out and wiped for excess water and then weighed. Tensile tests were performed using a Rheometric Scientific Minimat Firmware 3.1, at room temperature (22 °C). 15 samples of 5 × 2 mm were uniaxialy pulled at a speed of 5mm/min. From the stress-strain curves, the experimental elastic tensile modulus (Ec), the tensile strength (σu) and the elongation at break (εu) were determined.

3. Results and Discussions Transmission electron micrographs obtained from a dilute suspension of chitin nanowhiskers. are presented in Figure 1a The suspension contains individual chitin fragments composed of slender parallelepiped rods that have a broad length distribution. These fragments have a length ranging from 50 nm up to 500 nm, and a width from 5nm up to 30nm. Nanowhiskers lengths are presentd using cumulative frequency curve at Figure 1b. The dimensions of the nanowhiskers were averaged from the analysis of 5 micrographs and more than 100 rods were analysed.

The average length was found to be 303 nm and the average width 19.9nm. The average aspect ratio (L/d, L being the length and d the diameter) of these nanowhiskers is 15.9.

Dimensions are similar to other previously reported works for chitin nanowhiskers from shrimp shells with lengths ranging from 150 to 500nm and widths close to 20 nm[30].

Polímeros, 28(1), 69-75, 2018

Reinforcement of poly (vinyl alcohol) films with alpha-chitin nanowhiskers

Figure 1. (a) TEM image of alpha-chitin nanowhiskers; (b) Histogram summarizing the determined lengths.

Table 1. Summary of DSC analized results for the nanocomposites.

Nanowhiskers Volume Fraction (%) 0 1.5 3.0 5.6 10

Tg (°C)

Tm (°C)

74 119 122 138 -

199 208 210 >250 >250

The infrared spectrogram in Figure 2 shows the presence of three typical peaks of alpha-chitin, observed for wave numbers 1658, 1622 and 1556 cm-1 corresponding to absorption of carbonyl group. The purity of the nanowhiskers can also be proven by the absence of proteins as indicated by the absence of absorption around the peak at 1540 cm-1[31].

The deacetylation degree values, determined by the method elaborated by Brugnerotto et al., are very low, around 17% (significantly below 50%)[32].

The glass transition temperature (Tg) is a measure of the energy needed to allow movement of the polymeric chains on the amorphous domains. At this temperature the polymer becomes softer and when a force is applied, amorphous chains easily slip between each other. In Figure 3 it is presented the thermograms for all samples, with Tg being determined at the point of inflection of the first change in the slope and the melting temperature (Tm) at the endothermic peak.

Calorimetric characterization presented significant changes in the glass transition temperature, while for melting temperature (Tm), small increases were detected, as described in Table 1. The glass transition temperature of films with pure PVA is 74.7 °C and with only 1.5vf% NWCH, the value rose to 119 °C, corresponding to an increase of 45 °C. With increasing NWCH content, the differences in Tg are smaller and occur in a range of 20 °C. Given these results, it is considered that the NWCH have an anti-plasticizer effect within the PVA. The reason for this behaviour is related with the increased movement restriction of PVA chains adsorbed at nanowhiskers surface due to the establishment of hydrogen bonds between hydroxyl and acetyl groups from chitin with Polímeros, 28(1), 69-75, 2018

Figure 2. Infrared Spectrum of the chitin nanowhiskers.

Figure 3. Thermograms for the nanocomposites(exo up): A = 0%vf; B = 1.5%vf ; C = 3.0%vf; D = 5.6%vf; E = 10.0%vf.

71/75 71

Lisboa, H. hydroxyl groups from PVA, Roohani et al also reported an increase on Tg for highly hydrolyzed PVA samples when reinforced with cellulosic nanowhiskers[19].

With regard to Tm, a slight increase of the melting temperature was detected and a possible explanation may be related to strong interactions between the chitin nanowhiskers and PVA chains resulting in higher number of crystalline domains on the matrix thus requiring more energy to be become free. This explanation is supported by the high degree of PVA hydrolysis. Similar results were obtained by Roohani et al., while testing PVA with different degrees of hydrolysis and cellulosic nanowhiskers[20].

For 5.6 and 10%vf samples, the material degrades, and it is not possible to detect a melting temperature for both composites. The anti-plasticizer effect is not a disadvantage in terms of film production methodology, since the only method used for production was by solvent evaporation, which is considered a slow but productive method that enables the formation of the aforementioned network of interactions between chitin-chitin.

As mentioned before, PVA films lack chemical and mechanical properties while wet, so to understand if the inclusion of NWCH could be beneficial to lessen the hygroscopicity, the swelling index was determined using Equation 1 for pure and reinforced samples.

WS − WD = ×100 (1) Swelling (%) WD

The swelling behavior of pure PVA and reinforced films is ploted as a function of the submersed time at Figure 4.

For every sample, the degree of swelling increased sharply for the first 5-10min of submersion, after which had a gradual increase until it reached an equilibrium weight at approximately 40min. Pure PVA films had the highest swelling index with 417%, followed 1.5%vf NWCH with 378%, while 5.6%vf NWCH samples had the lowest sweeling value of 119%. These results are in agreement with similar works, where the equilibrium swelling values were between 350% and 540%[18]. Nair and co-workers, also reported that chitin nanowhiskers reduce the ability of a rubber based nanocomposite to swell in the presence of Toluene[33].

Two factors should be considered while analyzing the swelling behavior of PVA films: one is the large number of hydroxyl groups that attract water molecules and the other is the PVA chains mobility. One combined with the other causes absorbed water to displace PVA chain resulting in increasing of dimensions and swelling. Eventhough chitin nanowhiskers have a large number of hydroxyl groups and thus attract more water molecules, this is overcomed by the reduction of the PVA chains mobility explaining the reduction of the swelling index.

Mechanical properties were assessed using tensile tests on small samples of nancomposite films. The obtained elongation at break and tensile strength for each volume fraction are displayed at Figure 4 and summarized at Table 2.

Analysing Figure 5, the results present an increase in the tensile strength required to break apart the nanocomposite film, and a decrease in the elongation sustained by the film, resulting in a composite with lower elasticity. A possible explanation for such result might be related with the presence 72 72/75

Figure 4. Swelling index for pure and reinforced samples: □ pure PVA; ∆ 1.5%vf; ○ 3.0%vf; ◇ 5.6%vf.

Table 2. Summary of the composite films mechanical properties.

NWCH Volume Fraction

Tensile Strength

Elongation at Break

(%)

(MPa)

(%)

0 1.5 3.0 5.6 10

6.3 ± 0.2 6.8 ± 1.5 10.6 ± 2.6 23.5 ± 2.3 49.8 ± 4.5

202.0 ± 33.9 65.6 ± 2.5 43.1 ± 5.6 15.9 ± 1.7 10.3 ± 0.3

Elastic modulus Modulus (MPa) 100 110 208 320 937

of the hydrogen bonding between the nanowhiskers and PVA chains reducing mobility and resulting in a material with lower elasticity but providing reinforcement to the whole film structure. Similar results were reported by different authors[34-36].

NWCH mechanically reinforce the matrix of PVA but to better understand the reinforcing effect of the NWCH on the PVA nanocomposite films, theoretical values were calculated using two different models. The classical phenomological series-parallel model of Takayanagi et al.[37,38] that accounts for a percolating network where the fillers interact by hydrogen bonding forces above a calculated volume fraction. In this approach the composite elastic tensile modulus, Ec, can be calculated using Equation 2.

Ec =

(1 − 2 ⋅ ψ + ψ ⋅ vr ) ⋅ ES ⋅ ER + (1 − vr ) ⋅ ψ ⋅ ER2 (2) (1 − vr ) ⋅ ER + ( vr − ψ ) ⋅ ES

where the subscripts R and S refer to a “rigid” phase and a “soft” phase, the reinforcement agent and the matrix, respectively. The parameter Ψ is a correction factor of the nanowhiskers volume fraction enrolled in percolation and can be determined by Equation 3.

Polímeros, 28(1), 69-75, 2018

Reinforcement of poly (vinyl alcohol) films with alpha-chitin nanowhiskers

Figure 5. Tensile Strength at break (a) and Elongation at break (b) for each composite with with different nanowhiskers volume fraction.

Table 3. Values used by both models while calculating simulations.

= ψ 0, vr ≤ vrc v −v  ψ= vr ⋅  r rc   1 − vrc 

0.4

, vr > vrc

(3)

Where vr is the nanowhiskers volume fraction and vrc is the percolation threshold (the lower volume fraction where the percolation phenomena begins). Using this model, above a volume fraction of 4.4%vf a dramatic increase in Elastic modulus’s is expected, and should be linked to the percolation phenomena, since it’s the calculated percolation threshold for an aspect ratio of 15.9[39]. Above percolation, the establishment of a NWCH network is be responsible for the gradual increase of the elastic tensile modulus.

The Halpin-Tsai model[40] was formulated for composites reinforced with well dispersed, continuous and aligned fibers, and modified by Nielsen for short fibers[41]. This model can also predict the elastic tensile modulus using Equation 4.

EC = ES

1 + ξ B vr (4) 1 − Ω B vr

where, ξ =2

L (5) D

and, ER −1 E (6) B= S ER +ξ ES

and, 1− Φ Ω = 2 m Vr (7) Φm

Using the shape parameter ξ, related to the reinforcement geometry and the load direction, the Halpin-Tsai equations can be used to estimate the elastic tensile module for short fiber reinforcement as proposed. With the parameter Ω the model Polímeros, 28(1), 69-75, 2018

Notation Parameter Value ES Elastic tensile modulus of soft phase 100 MPa ER

Elastic tensile modulus of rigid phase 2000 MPa[43]

ξ

Shape parameter

31.8 (aspect ratio 15.9)

vrc

Critical volume fraction

4.4%

Φm

Adjustment factor

0.17

takes into account the maximum fraction of reinforcement admitted by a composite system, ϕm. This value is dependent on the particle geometry and packaging, for example, for a cubic packing ϕm takes a value of 0.785 and for hexagonal packing a value of 0.907 is used[42]. These high values are typical of aligned continuous fiber composites. In the case of composites with nanowhiskers as reinforcement, the nanoparticles are arranged randomly, and can take values considerably lower[42]. Due to uncertainty regarding the maximum fraction of reinforcement and its dependence on both the alignment and the aspect ratio of the reinforcement, ϕm is used as an empirical adjustment factor in the equations of Halpin-Tsai. The parameters used in boths models are summarized in Table 3.

Analysing Figure 6, the series-parallel model (Percolation) is not in agreement with the values obtained experimentally.

It should be noted that this model is widely used for modeling experimental data for composites reinforced with cellulose nanowhiskers. As result, one explanation for the failure in the setting of this model can be the hypothesis of the formation of a percolation network, or the lack of such molecular structure.

This network is established due to the formation of links by hydrogen bonds between cellulose nanowhiskers. For chitin nanowhiskers, possibly these links are hampered by the presence of acetyl groups and amine groups on the surface, resulting in lower interactions between chitin microcrystals.

The ineffectiveness of the series-parallel model to fit the experimental results can also be related to the fact that the occurrence of a percolation network is either more likely has greater the difference between the Elastic tensile modulus of the matrix and the nanowhisker. Morin and coworkers 73/75 73

Lisboa, H. reduced mobility of amorphous and crystalline PVA chains around the nanowhiskers particles resulting in increases of glass transition temperature and melting temperature.

Swelling index was also reduced by the inclusion of chitin nanowhisker resulting in films with higher moisture resistance. The tensile tests results presented an increase in the elastic tensile modulus and tensile strength revealing a reinforcement of the mechanical properties. While applying boths model to the elastic tensile modulus experimental results it was clear that the reinforcing mechanism is related to the nanowhiskers packing in the matrix and not to the percolation phenomena as initially thought.

5. References

Figure 6. Plot comparing the Halpin-Tsai and Percolation(Series Parallel) models with experimental results.

found that this model was unable to predict the elastic tensile modulus of composite PCL/NWCH, because the difference between the elastic tensile modulus of the matrix and nanowhiskers was not significant[43]. In fact, when the s tensile modulus of the two phases are close (a difference of one order of magnitude or lower) the influence of the percolating rigid phase is negligible at low reinforcement concentrations, such as those used in this work. In this case, the mechanical properties do not suffer an abrupt change, as predicted by the percolation model, and depend on the homogeneity of the composite[44].

Thus, it was used the Halpin-Tsai model in order to predict the composite elastic tensile modulus´s. The values of the parameters used in this model are listed in Table 3.

As shown from Figure 6, with Halpin-Tsai equations the obtained values for the elastic tensile modulus are very close to the values obtained experimentally. This suggests that the packing of NWCH plays a more important role reinforcing the polymeric matrix. In fact, good correlation between the experimental values of elastic tensile modulus with those obtained by this model seems to suggest that there is no percolation phenomenon in these composites. The low value of the maximum fraction nanowhiskers used was provided by Nielsen[41,42] for composites with short fibers randomly arranged in space, such as those studied here.

Finally, Halpin-Tsai theoretical values assumes perfectly dispersed and homogeneised nanowhiskers on the matrix so, for this reason, small differences between the experimental and theoretical values were obtained[44].

4. Conclusions In the present work, pure alpha-chitin nanowhiskers were produced and successfully added to thermoplastic PVA films. From the thermal transitions analysis it was concluded that nanowhiskers provided an anti-plastifying effect due to 74 74/75

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Received: July 14, 2016 Revised: May 19, 2017 Accepted: June 16, 2017 75/75 75

ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.02617

O O O O O O O O O O O O O O O O

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams Maciej Combrzyński1*, Leszek Mościcki1, Anita Kwaśniewska2, Tomasz Oniszczuk1, Agnieszka Wójtowicz1, Magdalena Kręcisz1, Bartosz Sołowiej3, Bożena Gładyszewska2 and Siemowit Muszyński2* Department of Food Process Engineering, University of Life Sciences in Lublin, Lublin, Poland 2 Department of Physics, University of Life Sciences in Lublin, Lublin, Poland 3 Department of Milk Technology and Hydrocolloids, University of Life Sciences in Lublin, Lublin, Poland 1

*maciej.combrzynski@up.lublin.pl; siemowit.muszynski@up.lublin.pl

Abstract The aim of this work was to determine selected physical properties of biodegradable thermoplastic starch (TPS) filling foams manufactured by extrusion-cooking technique from different combinations of potato starch and two additives: poly(vinyl alcohol) PVA and Plastronfoam PDE. Foams were processed with seven starch/additives combinations at two different extruder-cooker’s screw rotational speeds. The densities of starch foams depended significantly on the additive type and content. The linear relationship between the Young modulus and the ultimate compression force and apparent density was found. The foams processed with the addition of PVA had low density, porosity and lower values of the Young modulus than the foams prepared with PDE. Keywords: extrusion-cooking, thermoplastic starch foams, protective loose-fill materials, physical properties, functional additives.

1. Introduction With the current focus on environmental credentials, producers of packaging foam materials are under growing pressure to develop products based on natural renewable raw materials[1-4]. The pro-environmentally oriented consumers are becoming increasingly aware that the use of petroleum-based non-degradable packaging for short‑term use is not adequate[5-7].

Therefore, the search for safer, environmentally friendly packaging materials has become an important issue in developed countries and promoted the development of biopolymer-based materials, such as the packaging materials manufactured on the basis of completely biodegradable thermoplastic starch (TPS) [8-12] . To succeed, the TPS-based packaging must comply with the quality and safety requirements[13,14]. It is also important, that it could be processed with the standard equipment used in plastic processing.

According to the granular structure of starch there have been observed several negative characteristics for strachy products. Increased amount of starch in blends resulted lowering the mechanical properties of biopolymers as reported by Nafchi et al.[15]. There are many works available describing the mechanical properties of TPS-based materials[16-22].

The mechanical features of starch-based bipolymers are strongly dependent on the type and amount of additives used, mainly plasticizers and elastomers. Many authors also examined the behavior of starch-based blends[23-25]. In this case starch was bound with other biopolymers, often with biodegradable polyesters, like polycaprolactone, polyester amide or with polylactide acid (PLA)[26-28]. For example, the addition of PLA increased the mechanical properties and resistance to water of final products[15]. TPS/PLA blends are characterized by improvement in thermal stability, inhibition

76 76/83

of starch retrogradation and higher resistance to water at high relative humidity[29-31].

Other auxiliary materials, like poly(vinyl alcohol), assist in controlling the adhesive properties of the material surface[32-34].

The results of application of glycerol as plastycizer showed reduced stiffness and improved fracturability of starch-based foams. Moreover, poly(vinyl alcohol) has to be indicated as an effective additive able to decrease water absorption in biobased foams[35,36]. These types of materials may be used as alternative environmentally friendly packaging materials with cushioning features.

As described by Kaisangsri et al.[37] the addition of plant fibers to foamed materials based on starch improved the mechanical characteristic of these products, especially as bending resistance and compression resistance The opposite characteristics were found by Carr et al.[38] if manioc fibers was used as an additive and decreased mecanical strength of foamed materials was observed. The increase in fibers quantity has resulted in foams with higherdensity and less flexibility, whatever the fiber type. Mostfibers quantity did not improve the foam strength. Steven et al.[39] concluded that strength of foams at the bending tests was similar for starch-lignin foams compare to polystyrene foams, and the maximum stress results were lower while elastic modulus was higher for starch-lignin biopolymers. Classification of foamy materials could be based on the mechanical characteristics, especially elastic modulus[4]. Physical properties of foams are extremaly important for practical application of starch-based products. For these reasons several tests as compression, elongation, or bending could be performed for

Polímeros, 28(1), 76-83, 2018

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams the evaluation of Young modulus, compression stress and strain or breaking resistance. The idea of polymer-starch blends gave the possibility to achieve products undergo dezintegration or degradation without lowering the functional and mechanical properties[3,6,40].

Several works have been done for imporovement of physical and mechanical properties of starch-based biopolymers, but still there are a lot of possibilties to apply several components and functional addtives to create desirable characteristics of final products depend on applications and needs of final users.

This paper provides an approach aimed at examining the selected structural characteristics as density, porosity and mechanical strength of new type of biodegradable loose-fill cushioning foams based on potato TPS enriched with two functional additives– poly(vinyl alcohol) PVA and Plastronfoam PDE processed under various screw speed of extruder.

2. Materials and Methods 2.1 Materials and samples preparation Potato starch of the Superior Standard type (PPZ Trzemeszno, Trzemeszno, Poland) with amylose content of 26.97% was used in this study. The moisture content of the starch was 16.7% and the pH 7.4. The extrusion-cooking process parameters and raw materials and additives were selected on the base of the preliminary study. First step included application of selected additives as glycerin, PDE, PVA, guar gum, xanthan gum, gelatin, sodium dicarbonate, albumin, carrageenan, monoglyceride E471, mineral talc. These additives were used as foaming, emulsifying or stabilizing agents for the proper structure of starch-based foams. The results of most of the additives used were not satisfactory for products’ quality so the only two were selected for further tests. As the functional additivies Plastronfoam PDE as a white powder (VGT Polska Sp. z o.o., Kraków, Poland) and poly(vinyl alcohol) PVA as a white powder (Avantor-POCH S.A, Gliwice, Poland) were used. The control blend, containing only potato starch was prepared and six experimental blends, enriched with functional additives, PVA or PDE were prepared as presented in the Table 1. In total, seven various raw materials blends were prepared. Also, the necessary amount of water was added to the mixtures, so the total moisture content of all prepared blends was 18%. The blends were mixed for 20 minutes in a laboratory ribbon mixer until homogeneous mass was obtained.

The extrusion-cooking process was carried out using a single screw extrusion-cooker TS-45 (Z.M.Ch. Metalchem, Gliwice, Poland) with L/D = 12. The screw rotational speed was set at 100 or 130 rpm, so 14 different types of foams were produced (7 different blends processed at two different screw rotations), as presented in the Table 1.

The temperature profile along the barrel sections (from the feeding zone to the die) was similar for all treated blends and varied from 80 up to 100 °C. A forming circular die with the internal diameter of 5 mm was selected for the experiment, and thus annular cross-section samples were obtained, single foam characterized the size of 20 mm in length and approx. 10 mm in diameter depends on expansion Polímeros, 28(1), 76-83, 2018

intensity. In total, After the extrusion-cooking, the foams were cooled down at room temperature and dried in an air oven at 40 °C for 24 h. Examples of the tested foams are presented in the Figure 1.

2.2 Determination of true and appearent densities Measurements of the true and apparent densities as well as porosity were evaluated for all the samples processed at various conditions. The apparent (bulk) density was measured by a GeoPyc1360 dry flow pycnometer (Micromeritics, Inc., Norcross, GA, USA) with the consolidation force of 50 N, while the measurements of the true density (or material density) of foam slices was performed with the AccuPyc 1330 helium gas pycnometer (Micromeritics, Inc., Norcross, GA, USA). All measurements were performed with 5 repetitions.

The parameters of the measurements of both densities were described in details by Muszyński and coworkers[41].

The apparent ρe and true ρt densities (g⋅cm-3) of samples were determined and the results were used to calculate porosity P (in %) and specific pore volume SPV (cm3⋅g-1), according to Equations 1 and 2:  ρ  P= 1 − e 100% (1)  ρt  = SPV

1 1 (2) + ρt ρe

where: P = porosity (%), ρe = apparent density (g⋅cm-3), ρt = true density (g⋅cm-3), SPV = specific pore volume (cm3⋅g-1).

2.3 Mechanical measurements The mechanical properties were examined with a Zwick BDO-FBO0,5TH universal testing machine (Zwick GmbH & Company KG, Ulm, Germany), linked to a computer with testXpert II 3.3 test software (Zwick GmbH & Company KG, Ulm, Germany). Compression test was applied between two flat plates with dimensions of 100×100mm each, bottom plate was stationar and upper plate was movable with the test speed of 3.0 mm s-1. The foams were placed horizontally Table 1. Sample coding scheme depending on the functional additive percentage content and speed of the extruder-cooker screw.

Sample code C100 1PVA100 2PVA100 3PVA100 1PDE100 2PDE100 3PDE100 C130 1PVA130 2PVA130 3PVA130 1PDE130 2PDE130 3PDE130

Blend composition (g/g) Potato starch

PVA

PDE

100 99 98 97 99 98 97 100 99 98 97 99 98 97

0 1 2 3 0 0 0 0 1 2 3 0 0 0

0 0 0 0 1 2 3 0 0 0 0 1 2 3

Extruder-cooker screw speed (rpm) 100 100 100 100 100 100 100 130 130 130 130 130 130 130

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Combrzyński, M., Mościcki, L., Kwaśniewska, A., Oniszczuk, T., Wójtowicz, A., Kręcisz, M., Sołowiej, B., Gładyszewska, B., & Muszyński, S.

Figure 1. The structure of starch foams obtained at 130 rpm: (a) control foam; (b) foam with 3% PDE addition; (c) foam with 3% PVA addition.

on a flat plate, so that both compression plates were perpendicular to the axis of the sample, therefore the samples were compressed in the direction parallel to their diameter.

The measuring head compressed the sample in one cycle to 50% of its original diameter. Measurements for each foam type were performed with 10 repetitions. From the obtained stress-strain curves the following structural parameters were determined: the ultimate compression force (N) as the force causing sample fracture, and the Young modulus (MPa) as the deformation resistance of the foam[42-44].

2.4 Statitical analysis The statistical analysis of the structural characteristic (densities, porosity) and mechanical properties (Young modulus, ultimate compression force) of starch foams was performed with the software package Statistica 12.0 (StatSoft Inc., Tulsa, OK, USA) following a general linear model (GLM). The statistical model included the following variables: the functional additive type and content and the screw rotational speed as well as interactions between the screw rpm and functional additive type. Mean values were compared by Tukey’s multiple comparison test, the probability level of p<0.05 was considered as statistically significant. A two-dimensional linear Pearson analysis was used to calculate the corresponding correlation coefficients 78 78/83

(r values) between the structural characteristics of tested foams and the mechanical strength (Young modulus and ultimate compression force); p value <0.05 was considered as statistically significant.

3. Results and Discussions The two of functional additives showed various effect on starch-based foams according to its functionality nd technological approach. Plastronfoam PDE is the foaming agent dedicated for processing temperature up to 210 °C for a maximum gas yield, suitable as a blowing agent in plastic extrusion as well as injection molding. This is endothermic multi-component system, based on sodium bicarbonate and citric acid derivatives, starting its decomposition at 140 °C. Polyvinyl alcohol (PVA) is a particularly well-suited highly polar synthetic polymer for the formulation of blends with natural polymers. In the study of Shen et al.[45] polyvinyl alcohol (PVA) was used to improve the toughness of UF foam.

Polyvinyl alcohol has a high tensile strength and flexibility and has been used in UF resin synthesis for commercial use.

Therefore, to obtain an excellent foam material the proper amount of added PVA affected on superior toughness, compression strength, and morphological characterization of UF foams. According to Wang et al.[46] chitosan/PVA foams Polímeros, 28(1), 76-83, 2018

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams demonstrated interconnected and open-cell structures with large pore size.

The control foams (C100 and C130) varied considerably compared with the foams enriched with functional additives, in terms of their structural characteristics (Figure 1a), its structure was irregular with the presence of big internal empty cells after water evaporation during expansion. Addition of PDE influenced positively on foams structure giving the homogenous internal structure with a large number of smalluniform cells formed during the expansion of samples (Figure 1b). This structure was the most desirable and the samples with PDE addition, especially with 2 and 3% of PDE content, characterized compact structure less resistant for external deformations. If PVA was used as an additive the samples characterized with higher dimension of internal cells but much smaller than observed in control sampled without additives (Figure 1c).

The results of both apparent and true densities found for samples with the addition of PDE and PVA were significantly lower than for the control foams, especially there is clear evidence of decreased the apparent density of foams with foaming agents (Table 2). Similarly, the porosity and specific pore volume were the lowest for the extruded foams processed with addition of PDE among the all the tested extrudates.

Moreover, the screw speeds applied during the extrusion‑cooking of control samples have no significant effect on the structural characteristics and mechanical properties of control foams, the only values of the apparent density significantly decreased from 0.439 to 0.379 g⋅cm-3 (reduction of 14% was observed, p<0.05) when increased screw speed was applied during processing. In contrast, there was observed an effect of the screw speed on the structural properties of foams containing functional additives. In the case of foams with PVA there were significant differences between the true density of the foams containing 1% of PVA extruded at 100 and 130 rpm (increase of 32%; values of

0.983 and 1.300 g⋅cm-3 for 100 and 130 rpm, respectively).

The apparent density of all tested foams with PVA addition decreased when the blends were extruded at higher screw speeds (decrease of 22%, 35% and 25% for foams with 1, 2 and 3% of PVA, respectively). However, the porosity values increased for 1PVA130 and 2PVA130 (for 15% and 8%, respectively) while the specific pore volume increased for 2PVA130 and 3PVA130 blends (for 45% and 31%, respectively).

In the case of foams extruded from blends containing the PDE functional additive, the extrusion higher speed significantly increased the true density (by 48%, 81% and 74% for blends containing 1, 2, and 3% of PDE, respectively) and porosity (by 14%, 15%, 29%, for blends containing 1, 2, and 3% of PDE, respectively) of tested extrudates, and decreased the specific pore volume of samples containing 1, 2 and 3% of PDE (8, 25 and 15%, respectively). Generally, with PDE application it could be noticed that with an increase of the functional additive content a significant reduction of true and apparent densities was observed. Also, the values of true and apparent densities were significantly greater for PVA supplemented foams than for those extruded with PDE. Similarly, both the porosity and specific pore volume depended significantly on the functional additive type and content and a greater value of specific pore volume was observed for PDE foams. The results of compression tests, presented in the Table 3, showed that control starch foams extruded with various screw speed were characterized with the greatest ultimate compression force (204.1 and 162.9 N, for C100 and C130, respectively).

Moreover, these samples were characterized by a significantly greater Young modulus. For both functional additives it can be noticed, that with an increasing amount of the functional additives in blends the decrease of mechanical parameters was observed, irrespective of the functional additive type. Typical curves of compression tests for samples extruded at 130 rpm are shown on Figure 2.

Table 2. The structural characteristics of starch foams.

Foam type C100 1PVA100 2PVA100 3PVA100 1PDE100 2PDE100 3PDE100 C130 1PVA130 2PVA130 3PVA130 1PDE130 2PDE130 3PDE130 p-value F.A.* p value S.S. p value F.A. x S.S.

True density (g⋅cm-3) 1.227 ± 0.107gh* 0.983 ± 0.062ef 1.198 ± 0.086fgh 1.406 ± 0.164h 0.635 ± 0.126bc 0.411 ± 0.070ab 0.262 ± 0.031a 1.202 ± 0.068fgh 1.300 ± 0.265h 1.068 ± 0.133efg 1.238 ± 0.160gh 0.938 ± 0.077de 0.743 ± 0.119cd 0.457 ± 0.041ab <0.001 <0.001 <0.001

Apparent density (g⋅cm-3) 0.439 ± 0.068h 0.295 ± 0.022f 0.289 ± 0.032f 0.235 ± 0.026e 0.184 ± 0.029cde 0.130 ± 0.007ab 0.109 ± 0.006a 0.379 ± 0.038g 0.231 ± 0.034de 0.187 ± 0.011cde 0.175 ± 0.019bc 0.181 ± 0.016bcd 0.160 ± 0.018abc 0.113 ± 0.011a <0.001 <0.001 <0.001

Porosity (%) 64.14 ± 4.74ab 69.81 ± 3.44bcd 75.61 ± 4.06def 83.15 ± 2.10gh 70.78 ± 2.65cd 67.79 ± 4.27bc 57.96 ± 5.05a 68.43 ± 3.30bc 81.77 ± 3.75fgh 82.27 ± 1.85gh 85.74 ± 1.85h 80.63 ± 1.55efgh 78.15 ± 2.98efg 75.05 ± 3.89de <0.001 <0.001 <0.001

Specific pore volume (cm3⋅g-1) 3.141 ± 0.69a 4.422 ± 0.245bc 4.334 ± 0.369bc 5.02 ± 0.589c 7.159 ± 0.980ef 10.222 ± 0.819g 13.07 ± 0.721h 3.496 ± 0.273ab 5.508 ± 0.729cd 6.298 ± 0.399de 6.595 ± 0.627ef 6.624 ± 0.531ef 7.69 ± 0.845f 11.14 ± 0.81g <0.001 0.723 <0.001

Means in the same column with different superscripts differ significantly (p<0.05). *F.A. = functional additive; S.S. = screw speed.

a-h

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Combrzyński, M., Mościcki, L., Kwaśniewska, A., Oniszczuk, T., Wójtowicz, A., Kręcisz, M., Sołowiej, B., Gładyszewska, B., & Muszyński, S. Table 3. The mechanical properties of foams with functional additives.

Foam type C100 1PVA100 2PVA100 3PVA100 1PDE100 2PDE100 3PDE100 C130 1PVA130 2PVA130 3PVA130 1PDE130 2PDE130 3PDE130 p value F.A.* p value S.S. p value F.A. x S.S.

Young modulus (MPa) 563.8 ± 87.7f* 404.0 ± 71.8e 414.5 ± 95.3de 373.1 ± 50.8de 387.3 ± 55.4e 314.7 ± 58.0cde 197.0 ± 56.3abc 566.5 ± 55.6f 371.4 ± 53.0de 310.2 ± 69.2bcd 206.1 ± 57.7ab 342.4 ± 57.9de 311.9 ± 68.9cde 127.1 ± 33.4a <0.001 <0.001 <0.001

Ultimate compression force (N) 204.1 ± 33.1c 100.0 ± 18.6b 88.0 ± 14.9b 88.4 ± 23.8b 69.0 ± 19.4ab 54.3 ± 15.8ab 30.0 ± 12.1a 162.9 ± 71.6c 86.4 ± 23.3ab 76.0 ± 43.0ab 60.7 ± 11.2ab 64.0 ± 31.1ab 57.2 ± 18.3ab 33.6 ± 14.0a <0.001 0.004 0.632

Means in the same column with different superscripts differ significantly (p<0.05). *F.A. = functional additive; S.S. = screw speed. a-f

However, some evident differences between PVA and PDE foams could be observed. The Young modulus of foams with PDE was among the lowest recorded values and their ultimate compression forces were the lowest of all types of examined extrudates (Table 3). Moreover, it can be stated that foams with the same amount of PVA as functional additive were characterized by a greater Young modulus when extruded at 100 rpm than at 130 rpm. However, the general influence of the interactions between the functional additive level and the screw speed applied during processing was not statistically significant at the ultimate compression force (p = 0.632). All of the above results allow drawing the conclusion that the foams extruded without functional additives were more flexible and were characterized by a higher mechanical strength.

Figure 3 shows the correlation between the apparent density and the measured structural properties – the Young modulus of the extruded starch foams. The calculated Pearson’s correlation coefficient revealed that significantly positive correlations were found. On the Figure 4 the correlation between the apparent density and the ultimate compression force of the extruded starch foams have been presented. The linear correlation coefficient values were relatively high and ranged from r = 0.963 for correlation

Figure 2. Typical curves of compression tests for samples extruded at 130 rpm: (a) control foam; (b) foam with 3% PDE addition; (c) foam with 3% PVA addition.

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Polímeros, 28(1), 76-83, 2018

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams between the apparent density and the Young modulus and r = 0.973 for correlation between the apparent density and the ultimate compression force were calculated.

In this study, selected physical properties were characterized on different foams, and the effect of the functional additive and extruder screw speed on the properties of starch-based

Figure 3. The correlation between apparent densities and measured structural properties - Young modulus of extruded starch foams: ♦ control foams extruded without functional additive; + foams extruded with poly(vinyl alcohol) PVA; ▲ foams extruded with Plastronfoam PDE. In each graph the determination coefficient of linear regression R2 and Pearson’s r coefficient of correlation are presented.

loose-fill cushioning foams was studied and evaluated.

The observed decrease of the apparent density of starch foams with an increasing screw speed is in accord with previously published results[47,48]. The higher screw speeds during the cooking extrusion increased the shearing forces inside the barrel and thus affected on more intensive thermomechanical treatment resulting better expansion and lower density of final products[9,10].

The structure of the matter in the cell walls of extruded starch products depends on ingredients and process conditions and results in different wall properties, which partially affects the global mechanical characterization of the product[48]. In our study, the high correlation between the apparent density and mechanical traits was observed. For all the tested foams an increase of the ultimate compression force and the Young modulus was noticed with an increasing apparent density, showing that the mechanical properties of foams depend on blends composition used. For extruded starch products, a power relation between mechanical strength and structural traits is generally found[49]. Ashby[50] proposed a power law model for nonfood cellular solids, in which the exponent n gave an indication of the type of cavities. In compression, the power index equal to 2 means that the cells are open, while it is equal to 3 when the cells are closed. However, in our study, since the linear relation was found, the power index was equal to 1.

These results are in accordance with other studies, where linear relationships between the modulus of deformability[51] or crushing strength[52] and structural parameters were found.

It is assumed that this type of relation is true of extrudates for which the basis formulae of blends are rather similar[51].

Furthermore, this clearly shows the specific tendencies in the mechanical properties of extrudates, according to the ingredients and process conditions.

4. Conclusions Several key properties relevant to protective loose‑fill cushioning foams were identified and experimentally determined. They include density, porosity, strength properties and the compression modulus. The densities of the starch foams depended significantly on the functional additive type and content. In general, foams made with PDE as the functional additive had better performance in term of stiffness than PVA foams, since PDE foams had low density, porosity and good shock absorbance (lower values of the Young modulus). The structural parameters of foams, as well as their mechanical strength, were significantly different between foams produced at different extruder screw speed.

Mechanical properties showed a mediocre correlation with the Ashby model for solid foams, as the linear relationship between the Young modulus and the ultimate compression force and structural parameters was found.

Figure 4. The correlation between apparent densities and ultimate compression force of extruded starch foams: ♦ control foams extruded without functional additive; + foams extruded with poly(vinyl alcohol) PVA; ▲ foams extruded with Plastronfoam PDE. In each graph the determination coefficient of linear regression R2 and Pearson’s r coefficient of correlation are presented.

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38. Carr, L. G., Parra, D. F., Ponce, P., Lugao, A. B., & Buchler, P. M. (2006). Influence of Fibers on the Mechanical Properties of Cassava Starch Foams. Journal of Polymers and the Environment, 14(2), 179-183. http://dx.doi.org/10.1007/s10924-006-0008-5.

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41. Muszyński, S., Świetlicki, M., Oniszczuk, T., Kwaśniewska, A., Świetlicka, I., Arczewska, M., Oniszczuk, A., Bartnik, G., Kornarzyński, K., & Gładyszewska, B. (2016). Effect of the surface structure of thermoplastic starch pellets on the kinetics

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of water vapor adsorption. Przemysl Chemiczny, 95(4), 865869.

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43. Filli, K., Sjöqvist, M., Öhgren, C., Stading, M., & Rigdahl, M. (2011). Development and characterization of extruded biodegradable foams based on zein and pearl millet flour.

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45. Shen, Y., Gu, J., Tan, H., Lv, S., & Zhang, Y. (2016).

Preparation and properties of a polyvinyl alcohol toughened urea-formaldehyde foam for thermal insulation applications.

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46. Wang, X., Chung, Y. S., Lyoo, W. S., & Min, B. G. (2006).

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50. Ashby, M. F., & Medalist, R. F. M. (1983). The mechanical properties of cellular solids. Metallurgical Transactions. A, Physical Metallurgy and Materials Science, 14(9), 1755-1769. http://dx.doi.org/10.1007/BF02645546.

51. Smolarz, A., Van Hecke, E., & Bouvier, J. M. (1989).

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52. Hayter, A. L., Smith, A. C., & Richmond, P. (1986). The physical properties of extruded food foams. Journal of Materials Science, 21(10), 3729-3736. http://dx.doi.org/10.1007/BF02403029.

Received: Mar. 16, 2017 Revised: July 28, 2017 Accepted: July 31, 2017

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ISSN 1678-5169 (Online)

http://dx.doi.org/10.1590/0104-1428.03016

O O O O O O O O O O O O O O O O

Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA Luciana Maria Guadagnini Araujo1 and Ana Rita Morales1* Department of Materials Engineering and Bioprocess, School of Chemical Engineering, Universidade Estadual de Campinas â&#x20AC;&#x201C; UNICAMP, Campinas, SP, Brazil

1

*morales@feq.unicamp.br

Abstract The compatibilization of recycled PP/PET blend with high and low concentration (20 and 5 phr) of elastomer functionalized by maleic anhydride (SEBS-g-MA) was achieved. Recycled polypropylene from plastic industry and recycled PET from post-consumer bottles was used. PP/PET blends: 80:20 w/w, 50:50 w/w and 20:80 w/w were prepared in an internal mixer for mechanical properties, thermal properties, morphology and rheological properties. SEBS-g-MA promoted compatibilization of the PP/PET blends and improved their properties. With an increasing compatibilization level, the refinement of morphology was observed in the PET rich blend. Compatibilized blends showed negative deviation in the PET glass transition temperature related to neat PET, demonstrating that compatibilization was very successful.

PET crystallization was accelerated in the blends due to PP presence that enhanced nucleation. It was found that the 50/50/20 blend showed huge potential for textile fiber application and that of 80/20/20 showed more intermediary properties than neat polymers.

Keywords: blends, compatibilization, PET, PP, recycled polymers, SEBS-g-MA.

1. Introduction In 1998 the world production of synthetic polymers exceeded 100 million tons per year, a quantity sufficient to annually wrap the Earth in foil of about one micron thickness[1]. The importance of this product in the world is huge thus, it is becoming increasingly important to recycle plastics. In the global context, Brazilian participation in the world production of thermoplastics resins of 6,5 million tons represents 2,7% of world production, being the most significant of Latin America[2].

Many of the materials that could be recycled in Brazil are still being sent to landfills and dumps. Plastic represents 20% of this volume, and it is the main recyclable product that is buried instead of being more appropriately destined for recycling. The environmental and economic potential wasted on the improper disposal of plastics is worth, on average, BRL 5.08 billion per year[2].

In less than 20 years, the recycling of post-consumer PET packaging created an entire industry in Brazil. In 2002, 105 ktons or 35% of all PET packaging was recycled and, in 2012, 331 ktons was recycled (almost 60%). This is a positive amount of recycling but this number could be higher if there was selective waste collection. For example, the destination of the recycled PET is for application in the textile industry. However if the aggregate value in recycled plastics is increased, maybe it can create a chain reaction and encourage policies for recycling plastics[3].

Polypropylene is a low-cost and easily processed material, which makes it excellent for use in the plastics processing industry, especially in the packaging industry.

PET is an excellent barrier property polymer, transparent and of good mechanical strength, making it the main polymer in manufacturing bottles and fibers. PET may enhance the

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stiffness of PP at higher temperatures while the polyolefin could facilitate crystallization of PET by heterogeneous nucleation, further raising blend stiffness[4,5]. In addition, the lower permeability of PET towards water vapor and oxygen could be usefully utilized in packaging materials, as the adequate morphology of the blend is achieved[4,6].

There are many studies to be found in the literature on polymer blends of PET and PP with different approaches, different functionalization strategies as well as different compatibilization and processing methods[4-9]. Recycled PET/PP and the functionalized elastomer (SEBS-g-MA) was studied in the following proportions: 50/50 and 67/33 ranging from 0 to 10% compatibilizer content and processed in a double screw extruder. The compatibilizer conferred good mechanical properties to the blend, leading to a change in the ductile and brittle behavior to improve the elongation and impact resistance. Furthermore, it reduced the average diameter of the PET particles in the matrix according to the concentration of the compatibilizer[7]. The compatibility of PP/PET by functionalization with acrylic acid leads to a finely dispersed morphology, good adhesion between phases, better processability during extrusion and superior mechanical properties, due to a reduction in interfacial tension as a result of enhanced interactions between the polar components of the blend[8]. A study with three types of compatibilizer was performed: one non-functionalized and two functionalized SEBS (GMA-g-SEBS and SEBS-g-MA in the proportions of 80/20 and 20/80). Used at 5% by weight it was observed that the compatibilizer SEBS-g-GMA was more effective in increasing the toughness and provided higher strength and modulus values. Both functionalized elastomers showed synergistic behavior in impact strength

PolĂ­meros, 28(1), 84-91, 2018

Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA results and the toughening effect was explained by the resulting morphology having a fine dispersion phase with droplets less well adhered to the matrix[9]. A comparative study of compatibilizing efficiency for PET/PP blend ranked the compatibilizers in the following order of efficiency: SEBS-g-MA ≈ PP-g-MA + TPO (thermoplastic polyolefin) >> LLDPE-g-MA ≥ PP-g-MA. The SEBS-g-MA performance can be attributed to its improved emulsifying power of the interface and to the presence of polystyrene block that prevented migration and loss in the polyolefin phase[4].

PET and PP are materials widely used in the fiber industry although their properties are vey distinct, for example PP has low Young’s Modulus and low recovery properties comparing to PET[10]. To achieve desirable properties is a goal in blends making what motivated this work, which objective was to evaluate the effect of the large range of concentration of the SEBS-g-MA in the compatibilization of recycled PET/PP blends. The originality and interest of this paper are pointed out on the use of both recycled polymers aiming to achieve good properties blends, especially for fibers applications.

2. Materials and Methods 2.1 Materials We used the following materials: commercial samples of isotactic Polypropylene (PP), MFI 6.5g/10min (recycled grade from scrap films produced and kindly supplied by Vitopel do Brasil Ltda); Poly(ethylene terephthalate) (PET), Intrinsic Viscosity: 0.82 g/dl, recycled flake grade (from post-consumer bottles produced by PET Flake do Brasil Ltda.); linear triblock copolymer SEBS-g-MA (commercial name FG-1901 and produced by Kraton Polymers), MFI 22 g/10min, content around 30% of polystyrene and 2% of maleic anhydride. The antioxidant additive Irganox 1010 (produced by BASF) was used during mixing to prevent polymer degradation.

2.2 Processing First flakes of PET were dried in a forced-convection oven for 12 hours at 120°C to reduce moisture content.

The materials PP/PET/SEBS-g-MA were pre-mixed all at once into a plastic bag manually before added into Rheometer chamber. The mixing equipment used was a Plasti-Corder Rheometer model W50EHT-3 Zones, from Brabender with an internal volume of 55 cm3. It was used the rotors type “Roller” capable of providing dispersive and distributive mixing, suitable for processing thermoplastics. Set up of mixing process was: mixing time of 8 minutes, wall temperature of 265°C and roller speed of 40 rpm. The mixing temperature was defined considering PET melt temperature at DSC analysis and degradation temperature of PP at TGA. The melt temperature was 246°C and PP initial degradation temperature was 287°C. Thin plates (thickness around 1 mm) were obtained by compression molding at a temperature of 275°C between two sheets of polytetrafluoroethylene.

The equipment used was a press model Q/F 8 tons from MH Equipamentos. The procedure took 2 minutes for heating, 1 minute for pressing and 2 minutes for cooling at 5°C. The blends were identified as ratio PP/PET/SEBS-g-MA, and always in this order.

Polímeros, 28(1), 84-91, 2018

2.3 Characterization 2.3.1 Rheology Rheology of melted blends was performed at parallel plates Hybrid Rheometer Discovery HR-2 of TA Instruments.

This equipment controls tension and the distance between the plates was 1 mm. The specimens’ diameter was 25mm.

Firstly, linear viscoelasticity region was determined by scanning deformation within a range of 0.1-10% at the frequency of 1Hz. Under linear viscoelasticity parameters, a deformation of 1% was settled in oscillatory shear for all samples, except for pure SEBS-g-MA (which was 0.25%) because it did not respond at 1% within the linear viscoelasticity parameters.

The temperature used for all samples was 280°C. 2.3.2 Microscopy Blends samples were fractured in liquid nitrogen, sputter-coated with gold between 20 and 30 nm of thickness and a filament current of 100 mA. Specimens were analyzed

by Scanning Eletron Microscopy FEI Inspect 5S, running at 20kV. For samples PP/PET 50/50, EDS (Energy Dispersive X-ray Spectroscopy) was conducted for determination of disperse phase/matrix.

2.3.3 Thermal analysis The thermal behavior of the blends was examined by DSC using a model Q-100 from TA Instruments and software TA Universal Analysis. Heating and cooling scans were carried out on 10 ± 1mg of material under a nitrogen flow within a temperature range of 25°C to 300°C at a standard rate of 10°C/min. The samples achieved equilibrium at 25°C and were melted at 300°C (first run) to erase thermal history; they were then cooled to 25°C and reheated to 300ºC (second run).

The phase-transition temperatures were determined at the maximum of the endothermic melting peak (Tm) and at the maximum of exothermic crystallization peak (Tc). The values of the enthalpies of melting (ΔHm) and crystallization (ΔHc) were calculated from the areas of the respective peaks. Indium was employed as a standard for temperature and enthalpy calibration. The % of crystallinity (Wc,h) was calculated from Equation 1 considering second heating. wc, h =

( ∆H m ) ∆H m,100% × f (1)

Where ΔHm,100% is the heat of fusion of polymer 100% crystalline (140 Jg-1 for PET and 165,3 Jg-1 for PP[11]), ΔHm is the heat of fusion measured and f is the mass fraction of polymer in the blend, TGA analysis was conducted to analyze the thermal stability of the blends. The thermogravimetric equipment used was a model Q-50 from TA Instruments. The heating rate was 10ºC/min room temperature until 1000°C under N2 atmosphere and gas flow rate was 40 ml/min.

2.3.4 Mechanical testing Injection molding was performed for mechanical testing specimens in a Haake Thermo Scientific Mini Injet II during 30 seconds at 265ºC to 275°C of melting temperature, molding temperature of 70°C and pressure of 500 Bar. Mechanical tests were performed at room temperature according to ASTM D638-10. Tensile strength was measured

by EMIC universal equipment model DL1000, speed rate of 5mm/min, specimen type V. For the IZOD Impact test, 85/91 85

Araujo, L. M. G., & Morales, A. R. blend samples were notched by Philpolymer equipment, model GT - 7016 - A2; the remaining length for break was 10.15mm. The angle of notched bars was 22.5° ± 0.5° each side, totaling 45° ± 1°. The IZOD impact test was determined

by EMIC equipment model AC-1, with a pendulum energy of 2.7J, according to ASTM D256-10. All the reported results are the average of at least five measurements.

3. Results and Discussions 3.1 Rheology The complex viscosity behavior of the neat components is shown in Figure 1. PET shows Newtonian behavior within the measured angular frequency (ω). PP shows a Newtonian plateau for low shear rates followed by a pseudo-plastic behavior with a viscosity drop with the shear

rate begins to appear from 1 rad/s. Pseudo-plastic behavior is very common for molten polymers and very useful for processing, this behavior appears due to the elastic nature of the molten polymer and the fact that under shear polymers tend to be oriented[12]. For SEBS-g-MA a typical behavior for elastomers of strong dependency of viscosity with shear rates or ω was observed.

The compatibilizer effect can be seen in Figure 2.

Uncompatibilized 50/50 blend and compatibilized 50/50/5 blend showed respectively predominantly viscous behavior, G” above G’ in almost all angular frequency ranges of the test. Compatibilized 50/50/20 blend showed elastic behavior at low frequencies and slight viscous behavior at high frequencies. The observed increase of G’ and G” compatibilized blends of 50/50/5 and 50/50/20 compared to uncompatibilized blend 50/50/0 due to the effect of the elastomeric compatibilizer.

Figure 1. Viscoelastic properties of neat components (PP, PET, SEBS-g-MA).

Figure 2. Viscoelastic properties of uncompatibilized and compatibilized 50/50 PP/PET blends (50/50/0, 50/50/5, 50/50/20).

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Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA Viscoelasticity properties of PP/PET blends with 20 phr of SEBS-g-MA are shown at Figure 3. The values of complex viscosity of the 50/50/20 blend is higher than 80/20/20 blend at low angular frequency. Considering the blend as a standard mixture, it was expected that the viscosity would be reduced, since it would be introducing a lower viscosity component (PET). In this case, 50/50/20 blend with a higher content of PET showed higher viscosity. It is evident that the 50/50/20 blend had better interaction and enhanced compatibilization.

3.2 Morphology SEM micrographs of PP/PET 50/50 uncompatibilized blend and compatibilized blends with 5 phr and 20 phr of SEBS-g-MA are shown in Figure 4a. In the uncompatibilized blend it is possible to observe a heterogeneous two phase system, where there are the continuous phase (matrix) and domains where the surface shows up very well defined and which characterize poor adhesion between the phases.

The large size of the dispersed phase is a result of the immiscibility of the blend components. Because PET is a polar polymer while PP is a nonpolar polymer, their blends are immiscible[10]. In order to determine which material

was the matrix and which was the disperse phase it was established by X-ray energy dispersive spectroscopy, which found 100% of carbon in the matrix and the presence of carbon and oxygen atoms in the dispersed phase at a ratio of 66 99% and 33.01% respectively, showing that the continuous phase was composed of PP and the discrete particles of PET. Also the rheologic results showed that the average viscosity of the PP was 197 Pa.s and PET was 49 Pa.s in accordance with others’ results found in literature (in the case of blends with equal amounts of the two components, the low viscosity component forms the discrete phase[7]). For compatibilized blends with 5phr and 20phr, Figure 4b and 4c respectively, clear improvement in the dispersion and adhesion between the phases was observed - even with 5phr of SEBS-g-MA. According to the interaction mechanism between maleic anhydride of SEBS-g-MA with hydroxyl groups of PET, the PET-MA-g-SEBS possibly formed during processing acts as a bridge between the two phases improving adhesion of the two polymers and the properties of the blend[7,13].

The probably mechanism of this interaction is shown at Figure 5, although a physical interaction, like hydrogen bonding, is also possible between PET and the maleic anhydride groups[13].

Figure 3. Viscoelastic properties of blends with 20 phr of SEBS-g-MA (80/20/20, 50/50/20, 20/80/20, SEBS-g-MA).

Figure 4. SEM micrograph of: (a) uncompatibilized 50/50 blend; (b) compatibilized 50/50/5 blend; (c) compatibilized 50/50/20 blend.

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Araujo, L. M. G., & Morales, A. R. SEM micrographs of PP/PET 80/20 compatibilized blends with 5 phr and 20 phr of SEBS-g-MA are shown in Figure 6. The compatibilizer provided a finely dispersed phase of PET in the PP matrix. In this case, the high content of SEBS-g-MA (20phr) does not show significant improvement at blend morphology for a high amount of PP. SEM micrographs of PP/PET 20/80 compatibilized blends with 5 phr and 20 phr of SEBS-g-MA are shown in Figure 7.

The inversion of the blend allowing PET to become the matrix shows the compatibilizer concentration effect. The compatibilization

was succeeded by a higher concentration of SEBS-g-MA, yielding a better homogeneity and a larger interphase area since dispersed phase domains reduction occurred. The blend with 5 phr of SEBS-g-MA shows large droplets and course phase separation. Thus, this low concentration is not enough to provide a fine dispersion in the PET matrix. In the PP rich system, the dispersed particles are smaller in size than those in the PET rich system. This difference is due to the lower viscosity of PET as compared to that of PP, which leads to more breakups of PET droplets in a PP matrix as compared to those of PP droplets in a PET matrix[10]. Moreover, viscosity

Figure 5. Interaction mechanism of maleic anhydride of SEBS-g-MA and PET[13].

Figure 6. SEM micrograph of PP/PET 80/20 blend (a) 5 phr of SEBS-g-MA (b) 20 phr of SEBS-g-MA.

Figure 7. SEM micrographs of PP/PET 20/80 blend (a) 5 phr of SEBS (b) 20 phr of SEBS-g-MA. 88 88/91

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Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA ratio has turned out to be one of the most critical parameters for the control of the morphology of blends. Generally speaking, if the minor component has lower viscosity than that of the main component, the dispersed phase will be uniformly and finely dispersed. Reciprocally, the minor component will be roughly dispersed if its viscosity is higher than that of the main component. It is generally admitted that the smallest particle size is achieved for a viscosity ratio around unity[14].

It is widely accepted that a compatibilizer has two main roles in the control of morphology of a blend, that is prevention of coalescence and reduction of interfacial tension[15]. In addition the block copolymer chosen should have physicochemical affinity towards both components in the blend. The general criterion is that each segment of the copolymer interacts with one of the blend components.

The improved properties are commonly attributed to improved adhesion at the interface of the dispersed phase and the matrix and to a reduction in particle size[16].

3.3 Thermal behavior The phase-transition temperatures of blends on the cooling and second heating runs in DSC are listed in Table 1.

The thermograms of the samples in all cases displayed single

crystallization (Tc) and melting peaks (Tm) of PP phase.

PET glass transition (Tg) for 20/80/5 and 50/50/0 blends did not show relevant change of temperature (up to 2°C) relative to recycled PET. These blends showed phase separation and large domains in the morphological analysis, revealing that insufficient amount of compatibilizer leads to lack of interaction between the polymers. However for the other blends, the glass transition temperature of PET varied between 4 and 9°C below, showing a certain level of miscibility due the interaction in the amorphous phase able to compatibilize the materials.

The melting behavior of the uncompatibilized and compatibilized blends did not significantly change. In the case of the PET phase, an increasing of more 20°C on the crystallization temperature (Tc) and on crystallization temperature (Tconset) relative to the pure PET was observed, according to Figure 8. It shows that PET crystallized in the presence of PP melted phase, which acted as a nucleating agent, reducing critical free energy for crystal consolidation and accelerating the crystallization process[17]. Moreover, the high pressure and temperature during the mixing process can promote the scission of the PET chains or transesterification yielding smaller chains which facilitates crystallization and result in an increase in Tc[17]. PET crystallization

Table 1. Transition Temperatures (Tc, Tm, Tg) and Crystallinity Degree (Wc,h).

Blends PET PP 80PP/20PET/5SEBS 50PP/50PET/5SEBS 20PP/80PET/5SEBS 50PP/50PET/0SEBS 80PP/20PET/20SEBS 50PP/50PET/20SEBS 20PP/80PET/20SEBS

Tc PP

Tc PET

Tm PP

Wc,h PP

Tg PET

Tm PET

Wc,h PET

(°C)

(°C)

(°C)

(%)

(°C)

(°C)

(%)

112 110 108 109 110 112 108 107

163 192 193 200 194 194 195 196

164 164 165 164 164 164 164 164

49 49 45 37 49 49 49 35

83 74 79 82 81 78 77 77

247 246 249 248 248 249 248 248

23 23 24 27 26 2 17 26

Cooling and heating rate: 10 °C/min.

Figure 8. DSC curves of cooling (a) focus on Tc of PP, (b) focus on Tc of PET. Polímeros, 28(1), 84-91, 2018

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Araujo, L. M. G., & Morales, A. R. degree was equal or up to 17% higher related to pristine polymer for all blends with exception of PP/PET 80/20/20 and 50/50/20 blends. This increasing of crystallization degree can be attributed to heterogeneous nucleation due to the surface of PP domains during cooling. In the case of 80/20/20 and 50/50/20, the decrease of PET crystallinity as the PET/PP ratio decreases may be due to the concomitant increase of the SEBS-g-MA/PET interaction where it acts hindering PET crystallization. PP crystallinity remains essentially constant since it is not involved chemically in the compatibilization interaction[4].

occurrence in the tensile test, and tended to fray at the end of the test. This feature could be interesting for textile fibers production and this behavior occurred only for this sample. It was a goal of this project that we found a special application for a blend.

The presence of SEBS-g-MA improved the impact resistance property. The compatibilizer acted as toughening agent absorbing much of the pendulum energy. As for the blends with 5 phr of compatibilizer the impact result was less representative. The non-compatibilized 50/50/0 blend had the lowest result of impact resistance followed by the PP/PET 20/80/5 sample. From the SEM analyses, both micrographs of these blends showed phase separation with large domains. It is interesting to note intermediary values of stress at break (σb) and the highest IZOD impact resistance due to PP ductile behavior characteristic in combination with the elastomeric compatibilizer. In Figure 9, it can be observed that the proportion of impact resistance results and toughness or Resilience Modulus, is a measure of the ability of a material to absorb energy until fracture[18].

These results are complementary because they were obtained from different trials. The use of the SEBS-g-MA, which provided a superior impact resistance for the blends relative to the neat polymer, also resulted in a significant increase in toughness, or improved final properties for applications requiring these characteristics. The observed mechanical behavior improvement could be explained by to effects: first the presence of a elastomeric phase in a relatively high amount that acted as energy absorber and also the interaction caused by the MA groups which helped on the stress transfer between the matrix and the more flexible domains.

Complementary studies comparing SEBS and SEBS-g-MA would be important to elucidate the isolated effects.

3.4 Mechanical properties The compatibilizer efficiency in the PP/PET blends was tested by analyzing the tensile strength and an IZOD impact test. The means of tensile and impact properties and the toughness of all examined blends are summarized in Table 2. The toughness or Resilience Modulus was calculated

by Origin Pro Student 2016™ software integrating the area under Stress-Strain curve.

Generally, in the tensile curve of the compatibilized blends, the stresses and strains were increased due to the addition of the elastomer compatibilizer, compared to the non-compatibilized blend. This is because of the nature of the elastomer that contains large chains and therefore improves the mechanical properties In the 50/50 ratio it is possible to observe the effect of the compatibilizer in the blend with equal concentrations of polymers PP and PET. In the 50/50/5 sample, all mechanical properties were enhanced compared to the non-compatibilized blend and the blend 50/50/20 showed 538% increase in impact resistance property against uncompatibilized blend 50/50/0.

Further, this sample showed ductile behavior, no rupture

Table 2. Tensile: Yield Stress (σy) Yield Strain (εy), Stress at Break (σb), Strain at Break (εb), Young Modulus (E), IZOD Impact Resistance and Resilience Modulus (UT).

BLENDS PP 80PP/20PET/5SEBS 80PP/20PET/20SEBS 50PP/50PET/0SEBS 50PP/50PET/5SEBS 50PP/50PET/20SEBS 20PP/80PET/5SEBS 20PP/80PET/20SEBS PET

σy

εy

σb

εb

E

IZOD

UT

(MPa) 31.3 ± 0,7 29.7 ± 0,8 24.4 ± 0,4 26.9 ± 4,3 32.5 ± 3,0 27.6 ± 0,9 19.3 ± 7,3 28.3 ± 4,0 39.3 ± 7,6

(%) 18 ± 1 19 ± 1 17 ± 1 12 ± 2 16 ± 2 15 ± 1 10 ± 2 11 ± 2 12 ± 1

(MPa) 33.1 ± 3,8 22.0 ± 0,7 34.8 ± 1,9 22.4 ± 5,7 29.7 ± 2,3 --19.2 ± 7,2 28.1 ± 3,9 39.1 ± 0,7

(%) 388 ± 37 162 ± 28 303 ± 170 13 ± 2 17 ± 2 --10 ± 2 11 ± 1 12 ± 1

(MPa) 939 1010 585 1148 1102 680 1822 1037 2756

(J/m) 29 ± 1 28 ± 1 98 ± 6 13 ± 1 18 ± 2 80 ± 5 15 ± 1 29 ± 2 15 ± 1

(J/m-3.104) 10195 ± 1121 3331 ± 596 9467 ± 469 184 ± 134 462 ± 381 2568 ± 900 65 ± 35 315 ± 296 130 ± 31

Figure 9. IZOD Impact Test results and Resilience Modulus (UT) and for all examined blends.

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Polímeros, 28(1), 84-91, 2018

Compatibilization of recycled polypropylene and recycled poly (ethylene terephthalate) blends with SEBS-g-MA

4. Conclusions The PP/PET blends in various ratios and at low and high content of the functionalized block copolymer SEBS-g-MA were studied in terms of thermal, rheological and mechanical tests. PET and PP blend is incompatible and shows two well-defined phases. Significant changes in the morphology of the blends were achieved with SEBS-g-MA, such as reducing the droplet size and better phase dispersion indicating the compatibilization between the polymers.

Besides a negative deviation on glass transition of PET was observed. These results indicates that physical or chemical interactions may have occurred between the MA of SEBS-g-MA and polar groups of PET. PET crystallization was accelerated and the degree of crystallinity was higher due to the presence of PP. As a consequence of all these effects and the presence of elastomeric behavior of SEBS it was possible to obtain blends with very good mechanical properties. The rheological properties showed a huge difference on viscosity of the recycled PET and PP so the compatibilization of them would be very challenging due to the low viscosity of the PET and the consequent lack of shear required to break the dispersed phase efficiently.

That is why a high amount of compatibilizer was required to yield better results of the phase dispersion and mechanical properties, manly for the PET rich blend.

We highlight the sample PP/PET 50/50/20 as a huge potential for fiber textile application, once it frayed during tensile test. Furthermore, this sample had good mechanical properties including impact resistance and a higher viscosity and storage modulus higher than the viscous modulus in the molten state, indicating an excellent elastic resistance during processing. Also the blend PP/PET 80/20 despite having good morphology with low compatibilizer content, only showed a high result of impact resistance, and better tensile properties when it was added 20 phr of SEBS-g-MA. This fact shows the importance of the elastomeric compatibilizer to improve the results even when the morphology indicates good homogeneity between the phases.

5. Acknowledgements The authors would like to thank the School of Chemical Engineering of Unicamp, 3M do Brasil for the use of laboratory analysis equipment. They would also like to thank Vitopel do Brasil, PET Flake do Brasil and Kraton Polymers for materials donations.

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Received: Mar. 15, 2016 Revised: Dec. 21, 2016 Accepted: Mar. 13, 2017 91/91 91

São Paulo 994 St. São Carlos, SP, Brazil, 13560-340 Phone: +55 16 3374-3949 Email: abpol@abpol.com.br 2018