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Asean Journal on Science & Technology for Development Contents

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Cover ASEAN AJSTD 34,2 2017.pdf

Vol. 34 No. 2, 2017 ISSN 0217-5460

A Journal of the ASEAN Committee on Science & Technology

ASEAN J. Sc. Technol. Dev. Vol. 34, No. 2, 2017

Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled Natural Rubber A.K. Norizah and S. Azemi

57

Assessment of Natural Radioactivity Level and Radiological Index in the Vicinity of Lynas Rare-earth Processing Plants W.M. Zal U’Yun, M.W. Yii, K. Mohd Ashhar, M.K. Khairuddin, I. Abdul Kadir and Y. Mohd Abd Wahab

67

Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM Using Unidirectional High-performance IO Standard B. Das and M.F.L. Abdullah

79

Adsorption and Diffusion Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocomposites R. Gunasunderi and M.R.H. Mas Haris

95

Preparation and Characterisation of Crosslinked Natural Rubber (SMR CV 60) and Epoxidised Natural Rubber (ENR-50) Blends M. Sasitaran, S. Manroshan, C.S. Lim, B.N. Krishna Veni, S.K. Ong and R. Gunasunderi

106

Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients Admitted to a Government Hospital ― A Cohort Study S. Sandasorroopan, K. Judenimal and R. (111) P. Dioso

119

Quantitative Analysis of Microcystin-LR in Drinking Water Comparing On-Line Solid Phase Extraction and Direct Injection LC/MS/MS R. Malarvili, Y.Y. Low and A. Zaiton

125

ASEAN Journal on Science & Technology for Development


ABOUT THE ASEAN JOURNAL ON SCIENCE AND TECHNOLOGY FOR DEVELOPMENT The ASEAN Journal on Science and Technology for Development is a refereed Journal of the ASEAN Committee on Science and Technology (ASEAN COST). It reports on science and technology policies and programmes, and research activities undertaken by COST in support of social and economic development of the ASEAN member countries. The coverage is focused but not limited to, the main areas of activity of ASEAN COST, namely, Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development.

ABOUT THE ASEAN COMMITTEE ON SCIENCE AND TECHNOLOGY The ASEAN Committee on Science and Technology was established to strengthen and enhance the capability of ASEAN in science and technology so that it can promote economic development and help achieve a high quality of life for its people. Its terms and reference are: ● To generate and promote development of region; ●

and technological expertise and manpower in the ASEAN

and from more advanced regions of the world to the ASEAN region;

● To provide support and assistance in the development and application of research discoveries and technological practices of endogenous origin for the common good, and in the more effective use of natural resources available in the ASEAN region and in general; and ●

projects.

Information on the activities of ASEAN COST can be obtained at its website http://www.asnet.org

DISCLAIMER While every effort is made to see that no inaccurate or misleading data, opinion or statement appears in the Journal, articles and advertisements in the Journal are the sole responsibility of the contributor or advertiser concerned. They do not necessarily represent the views of the Editors, the Editorial Board nor the Editorial Advisory Committee. and agents accept no responsibility or liability whatsoever for the consequences of any inaccurate or misleading data, opinion or statement.

© Copyright: ASEAN Committee on Science and Technology No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form of by any means, without permission in writing from the copyright holder.


ABOUT THE ASEAN JOURNAL ON SCIENCE AND TECHNOLOGY FOR DEVELOPMENT The ASEAN Journal on Science and Technology for Development is a refereed Journal of the ASEAN Committee on Science and Technology (ASEAN COST). It reports on science and technology policies and programmes, and research activities undertaken by COST in support of social and economic development of the ASEAN member countries. The coverage is focused but not limited to, the main areas of activity of ASEAN COST, namely, Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development.

ABOUT THE ASEAN COMMITTEE ON SCIENCE AND TECHNOLOGY The ASEAN Committee on Science and Technology was established to strengthen and enhance the capability of ASEAN in science and technology so that it can promote economic development and help achieve a high quality of life for its people. Its terms and reference are: ● To generate and promote development of region; ●

and technological expertise and manpower in the ASEAN

and from more advanced regions of the world to the ASEAN region;

● To provide support and assistance in the development and application of research discoveries and technological practices of endogenous origin for the common good, and in the more effective use of natural resources available in the ASEAN region and in general; and ●

projects.

Information on the activities of ASEAN COST can be obtained at its website http://www.asnet.org

DISCLAIMER While every effort is made to see that no inaccurate or misleading data, opinion or statement appears in the Journal, articles and advertisements in the Journal are the sole responsibility of the contributor or advertiser concerned. They do not necessarily represent the views of the Editors, the Editorial Board nor the Editorial Advisory Committee. and agents accept no responsibility or liability whatsoever for the consequences of any inaccurate or misleading data, opinion or statement.

© Copyright: ASEAN Committee on Science and Technology No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form of by any means, without permission in writing from the copyright holder.


Editorial Board Editor-in-Chief Emeritus Prof Md Ikram Mohd Said

School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia

Editorial Board Members Brunei Darussalam Dr Rahayu Sukmaria Sukri

Director of Research, Universiti Brunei Darussalam Asst. Prof Dr Tan Soon Jian

Director, Centre for Transport Research, Universiti Teknologi Brunei Siti Nirmala

ASEAN J. Sc. Technol. Dev. Editorial Advisory Panel, Deputy Permanent Secretary (Economy and Finance) Prime Minister’s Office Cambodia Phal Des

Vice-Rector, Royal University of Phnom Penh Indonesia Dr Sadjuga

Director of Intellectual Property Management, The Ministry of Research, Technology and Higher Education Dr Widodo

Head of Publishing and Publication Agency of the Universitas Gajah Mada Lao PDR Keonakhone Saysoulian Director of Data and Information Technology Department, Ministry of Science and Technology Phouthanouthong Xaysombath Director of International Organization and ASEAN

Division National COST Secretariat Focal Point, Department of Planning and Cooperation, Ministry of Science and Technology Myanmar Dr Theingi

Rector, Technological University (Thanlyin) Ministry of Science and Technology Philippines Dr Cynthia P. Saloma

Director, National Institute of Molecular Biology and Biotechnology, University of the Philippines Singapore Assoc. Prof Ong Sim Heng

National University of Singapore and Chairman of A*STAR Computational Resource Centre Thailand Prof Narongrit Sombatsompop

King Mongkut’s University of Technology,

Vietnam Asst. Prof Dr Hoang Minh

President, National Institute for Science and Technology Policy and Strategy Studies Le Thi Viet Lam

Deputy Director General and National COST Secretariat Focal Point, Department of International Cooperation, Ministry of Science and Technology


Bui Thi Thu Lan

Head of Division, General Affairs and Multilateral Cooperation Division, Department of International Cooperation, Ministry of Science and Technology

BĂši Quáť‘c Anh

Ministry of Science and Technology

Editor/Technical Editor/Executive Editor Kanesan Solomalai

Ex-Chief Editor, Academy of Sciences Malaysia Hazrul Liki

Academy of Sciences Malaysia

Production/Printers Perniagaan Normahs

Publisher Academy of Sciences Malaysia


Contents

ASEAN J. Sc. Technol. Dev. Volume 34(2), 2017

Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled Natural Rubber A.K. Norizah and S. Azemi

57

Assessment of Natural Radioactivity Level and Radiological Index in the Vicinity of Lynas Rare-earth Processing Plants W.M. Zal U’Yun, M.W. Yii, K. Mohd Ashhar, M.K. Khairuddin, I. Abdul Kadir and Y. Mohd Abd Wahab

67

Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM Using Unidirectional High-performance IO Standard B. Das and M.F.L. Abdullah

79

Adsorption and Diffusion Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocomposites R. Gunasunderi and M.R.H. Mas Haris

95

Preparation and Characterisation of Crosslinked Natural Rubber (SMR CV 60) and Epoxidised Natural Rubber (ENR-50) Blends M. Sasitaran, S. Manroshan, C.S. Lim, B.N. Krishna Veni, S.K. Ong and R. Gunasunderi

106

Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients Admitted to a Government Hospital ― A Cohort Study S. Sandasorroopan, K. Judenimal and R. (111) P. Dioso

119

Quantitative Analysis of Microcystin-LR in Drinking Water Comparing On-Line Solid Phase Extraction and Direct Injection LC/MS/MS R. Malarvili, Y.Y. Low and A. Zaiton

125


ASEAN J. Sci. Technol. Dev.,  34(2): 57 – 66

Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled Natural Rubber A.K. NORIZAH1 AND S. AZEMI2* The effect of coupling agent on tensile and tear strengths of vulcanized NR filled with 50 pphr of precipitated silica (VN3) was investigated. The amount of coupling agent was varied from 0,1,2,3,4,5 to 8 pphr. In the absence of coupling agent bis[3-(triethoxysilyl)propyl] tetrasulphide (TESPT), the tensile strength of silica-filled vulcanized NR was lower than the tensile strength of unfilled vulcanized NR. The enhancement in the tensile strength was achieved only when TESPT was incorporated into the rubber compound. The dependence of tensile strength on the amount of TESPT showed a similar trend as the dependence of tensile strength on the crosslink concentration. This might imply that varying the amount of TESPT was analogous to varying the crosslink concentration of the rubber network. The effect of TESPT on tearing energy was very striking in silica-filled vulcanized NR. Without Si69, the crack propagated in a steady (smooth) manner where the tearing energy increases with increasing test speed. When TESPT was added into the silica mix, the crack propagated sideways from the intended tear path producing the so called knotty tearing. The tearing energy was about a factor of ten higher than that without coupling agent in particular at low tear rates regions. The results here indicated clearly that in silica-filled vulcanized NR, coupling agent was essential to induce the strength anisotropy necessary for the occurrence of knotty tearing. The result also showed that TESPT also influenced the amount of hysteresis in silica-filled vulcanized NR. Both tensile and tear strengths were affected by the hysteresis. Key words: Coupling agent; TESPT; tensile strength; tearing energy; hysteresis; silane 69

Reinforcement of elastomers by colloidal fillers, like carbon black or silica, plays an important role in the improvement of the mechanical properties of high-performance rubber materials. The reinforcing potential is mainly attributed to two effects: (i) the formation of a physically bonded flexible filler network and (ii) a strong polymer–filler couplings (Vilgis 2009). Both of these effects arise from a high surface activity and the specific surface of the filler particles. Natural rubber is completely hydrocarbon and non-polar. On the other hand, the silica fillers 1

are polar in nature which need coupling agent to bond the rubber and silica fillers. Fὅhlich et al. (2005) stated that the silica fillers form a strong filler network with minimal interaction with the polymer chain but form a chemical linkage when a coupling agent is introduced. Coupling agent bis[3-(triethoxysilyl)propyl] tetrasulphide abbreviated as TESPT commonly known as Silane 69 has been found to be very effective. Choi and Kim (2002) reported that silane coupling agent enhanced the bound rubber formation by chemicals bonds between the

Advanced Rubber Technology Unit, Technology and Engineering Division, Malaysian Rubber Board, RRIM Research Station Sg. Buloh, 47000, Selangor, Malaysia

Iprus Sdn Bhd, C-3-1 Block C, Pacific Place Commercial Centre, Jalan PJU 1A/4, 47301 Ara Damansara, Selangor, Malaysia * Corresponding author (e-mail: azemi.sam@gmail.com) 2


ASEAN Journal on Science and Technology for Development, 34(2), 2017

silica and rubber. Vilgis et al. (2001) suggested that there are primary and secondary chemical reactions taking place that lead to chemical bonding between the silica fillers and rubber chains via TESPT as shown in Figure 1. It was reported by Park and Choo (2003), and Gent et al. (2003) that the organic functional group of silica surface lead to an increase of adhesion at interfaces between silica and the rubber chains resulting in an enhancement of crosslink density. Our concern here is to investigate the effects of the chemical bonding that formed at the filler surface and the rubber chains via TESPT on the mechanical strengths of vulcanized silica-filled NR. It is well established that mechanical properties such tensile and tear strengths are affected by the crosslink concentration. Apart from crosslink concentration, the strength and nature of chemical bonds bridging the filler surface and rubber chains also affect tensile and tear strengths.

Initial temperature of mixing chamber : 70oC

Rotor speed

: 110 rpm

Fill factor

: 0.7

Mixing sequence:

0 minute — Rubber

½ minute — All chemicals + ½ silica

1½ minute — Remaining ½ silica + Si69 + DEG

2½ minutes — Sweep

3½ minutes — Discharge.

The weight of each mix was recorded immediately after it was discharged and left overnight. Curatives were added on the 2-roll mill the next day. Mixing on the 2-roll mill was about 5 minutes. The finalized mix compound was sheeted out, cooled and stored at 23oC. The weight loss of all the eight mixes ranged from 0.38% to 1.6%. The recorded discharge temperature of the mixes ranged from 130oC – 140 o C. Samples were taken from each mix to determine their Mooney viscosity at 100oC by using Mooney viscometer and cure characteristics by using Monsanto Rheometer at 150oC.

EXPERIMENTAL Table 1 shows the formulations of the naturalrubber silica-filled compound. Natural rubber (SMR L) was used throughout. The amount of precipitated silica was fixed at 50 pphr, and the amount of coupling agent (TESPT) was varied from 1 to 8 pphr. Mix no. 1 was unfilled (gum) compound without any filler. Mix no. 2 served as the control compound containing 50 pphr of precipitated silica but without TESPT. Semi-EV sulphur vulcanization system was used throughout. There was an additional mix with 10 pphr of TESPT for the tear experiment.

Moulding of the test-pieces was done in an appropriate compression mould in an electrically heated press at 150oC. The cure time of each mix was referred to t95 of the rheometer torque-time chart.

All rubber mixes were prepared in a laboratory Banbury mixer (capacity 1600 cm3) with the following mixing conditions:

58


AK Noriah and Azemi S.: Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled NR

Figure 1. Chemical bonding that formed between rubber chains and silica surface via TESPT (Vilgis et al. (2003)). Table 1. Natural rubber silica-filled formulations. Mix no.

1

2

3

4

5

6

7

8

100

100

100

100

100

100

100

100

Zinc oxide

5

5

5

5

5

5

5

5

Stearic acid

2

2

2

2

2

2

2

2

Santoflex 13TM

3

3

3

3

3

3

3

3

Precipitated silica (VN3)

50

50

50

50

50

50

50

Si 69 (TESPT)

1

2

3

4

5

8

DEG

2

2

2

2

2

2

Sulphur

1.5

1.5

1.5

1.5

1.5

1.5

1.5

1.5

CBS

1.5

1.5

1.5

1.5

1.5

1.5

1.5

1.5

NR (SMR L)

All the ingredients are expressed as parts per hundred of rubber (pphr).

Tensile Test

Tear Test

Tensile strength and elongation at break were done by pulling a dumbbell test-piece at 500 mm per minute at 23 oC by using a tensile machine in accordance with ISO 37. The mean value from five readings were recorded.

Tearing was carried out by separating the legs of the trouser test-piece using an Instron tensile machine at test speeds ranging from 5 mm per minute to 1000 mm per minute. In the case of constant rate separation method, the tear 59


ASEAN Journal on Science and Technology for Development, 34(2), 2017

rate was half the crosshead speed (extension rate) (Samsuri & Thomas 1988; Greensmith & Thomas 1955). The tearing energy, T for the trouser test-piece was computed using Equation 1 given by Samsuri and Thomas (1988); and Greensmith and Thomas (1955). T = F (λ + 1) / h

at the test speed of 500 mm per minute. The hysteresis was determined from the area of the hysteresis loop (area bounded by the extension and retraction curves as shown by a schematic diagram in Figure 2) of the sixth cycle. Hardness Test

(1)

Hardness is defined as the resistance to surface indentation as measured under specified conditions. The test was done in accordance with ISO 48. A cylindrical test-piece (8 mm thick, 25 mm diameter) was placed underneath a spherical indentor where a specific load was applied for a specific time. The hardness reading was displayed electronically by the hardness tester.

where, F is the force to propagate tearing, λ is the extension ratio in the legs of the test-piece and h is the average nominal thickness of the test-piece. Hysteresis Test The test-pieces 75 mm × 10 mm × 1 ± 0.2mm were prepared by stamping a die on a flat vulcanized rubber sheet of uniform thickness. The test was conducted at 23 ± 2oC. The testpiece was clamped between the two grips of the tensile machine and the gauge length (40 mm) between the grips was noted. The test-piece was stretched to 300% strain and then relaxed it to zero strain. This process was repeated six times

RESULTS AND DISCUSSIONS The Rheological and Cure Charcteristics of Silica-filled NR Compounds The Mooney viscosity and cure characteristics of the silica-filled NR compounds are shown in Table 2. The Mooney viscosity of gum

Extension curve

Force Hysteresis loop

Retrac�on curve Extension

Figure 2. Schematic diagram showing the force-extension and retraction curves. The area bounded by the extension and retraction curves is known as hysteresis (Azemi 2008).

60


AK Noriah and Azemi S.: Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled NR

Table 2. Mooney viscosity (ML (1+4) 100°C) and optimum cure time (t95) of silica-filled NR compounds. Mix number

1

2

3

4

5

6

7

8

ML (1+4) 100°C

29.6

44.9

61.3

65

63.9

62

58.7

54.4

t95 (minutes) at 150oC

18

22

15

15

17

18

19

20

compound (Mix 1) was very low since there was no filler in the compound apart from ingredients necessary for vulcanization. Mixes 2 to 8 contained the fixed amount of filler (VN3) but varying amount of TESPT. It could be seen that Mix 2 produced higher Mooney viscosity by about 52% than the unfilled compound. This increase was associated with the hydrodynamic effect. The addition of TESPT increased the Mooney viscosity of the compound ranging from 22% to 40% depending on the level of TESPT. This further increase might be associated with the enhancement in the rubber-filler interaction that occur during mixing (Luginsland et al. 2021). The addition of silica increased the optimum cure time from 18 minutes (Mix 1, unfilled) to 22 minutes (Mix 2) because of the tendency of the silica

filler to absorb curatives associated with its surface ruggedness. Mixes 3 to 8 contained diethylene glycol (DEG) to minimize absorption of curatives by the filler. Consequently, the cure time is shortened. Effect of TESPT on Hardness of Vulcanized Silica-filled NR Before discussing the mechanical strengths (both tensile and tear), it is useful also to look at the hardness of the vulcanized rubber since it can be used to measure the degree of reinforcement. The hardness of gum (unfilled) vulcanized NR is 40.1 IRHD for this particular semiEV system. The addition of 50 pphr of silica increased the hardness markedly to 70 IRHD as shown in Figure 3. The results indicated that hardness increased progressively with

Hardness vs coupling agent TESPT 82

Hardness (IRHD)

80

80

78 77

76

76

74

74

73

72 70

71

70

68 0

1

2

3

4

5

6

7

8

Coupling agent TESPT (pphr)

Figure 3. Effect of TESPT on hardness of vulcanized silica-filled NR.

61

9


ASEAN Journal on Science and Technology for Development, 34(2), 2017

increasing amount of TESPT. The mechanism by which filler enhances the hardness and modulus is reasonably well understood, at least in qualitative terms. The stiffening is in part attributed to the absence of deformation within the rigid filler particles, and in part with the immobilization of the rubber at the interface between the rubber matrix and the filler particles as a consequence of two-network formation, plus the hydrodynamic effect (Liginsland et al. 2001; Vilgis et al. 2009). According to Vilgis et al. (2009) coupling agents such as TESPT have triethoxysilyl functions which can react with the silanol groups on the silica surface. This chemical reaction is known as ‘silanization reaction’. During the reaction, one ethoxy group of each Si-unit reacts with an accessible silanol group on the silica surface and, therefore, links chemically to the filler (Vilgis el al. 2009). The hardness increased with increasing amount of TESPT because of the enhancement of the twonetwork formation since the level of accessible silanol group was always high.

marked influence on the tensile strength of vulcanized silica-filled NR as shown in Figure 4. The tensile strength of gum (Mix 1) vulcanized NR is relatively high (22 MPa) because of its ability to strain crystallize during stretching. Indeed the tensile strength of gum vulcanizate was greater than silica-filled NR without coupling agent (Mix 2). At first sight, it is unthinkable that silica-filled vulcanized NR gives lower tensile strength than unfilled vulcanized NR. This is a perfect example of the compound nature of the mechanism of reinforcement of particulate fillers in vulcanized rubber. In the absence of efficient bonding or interaction at the rubber-filler interface, the expected reinforcement cannot be achieved. In the presence of coupling agent, silica-filled vulcanized NR gave markedly higher tensile strength than that of without coupling agent. This indicated the significant influence of coupling agent to enhance the rubber-filler interaction. It was interesting to note that the tensile strength increased with increasing amount of TESPT until it reached an optimum level. Above this optimum level of TESPT, the tensile strength decreased similarly as the

Influence of TESPT on Tensile Strength The coupling agent TESPT showed very

Tensile strenght vs coupling agent (TESPT) 40

Tensile Stranght (MPa)

34.6 35

33.8

36

33.8

33.6

28.7

30 25 20 20 15 0

2

4

6

8

10

Coupling agent TESPT (pphr)

Figure 4. Plot of tensile strength vs TESPT showing the influence of TESPT on tensile strength.

62


AK Noriah and Azemi S.: Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled NR

dependence of tensile strength on the crosslink concentration of the rubber network as shown in Figure 5. The same explanation might be put forward to explain the dependence of tensile strength on TESPT. The effect of increasing the amount of TESPT is analogous to increase the crosslink concentration. Azemi and Che Mohd (2013) found that the volume fraction, vr, of the rubber in the swollen gel increases with increasing TESPT as shown in Figure 6. The reduced swelling of silica-filled vulcanizates can reflect an increase in crosslinking efficiency of the vulcanizing system and hence a greater degree of actual crosslinking, or adhesion of rubber to filler particles, causing reduced

swelling near the particles even when the degree of crosslinking is unchanged (Gent & Hartwell 2003). At optimum TESPT, the network structure was already completed, and further insertion crosslink could only result in the tightening of the network. This, in turn, imposed an increasing number of restrictions on any molecular segment attempting to orientate and aligned with neighboring segments. The overall effect was that the degree of oriented crystallization fell and consequently the tensile strength decreased.

Tensile strenght vs crosslink concentration 30

Tensile Strenght (MPa)

25 20 15 10 5 0 0.01

0.02

0.03

0.04

0.05

0.06

0.07

Crosslink concentration [X]phy mol/kg

Figure 5. Dependence of tensile strength on crosslink concentration. Black-filled vulcanized NR (Samsuri 1989). Effect of pre-stressing on vr versus Si69 before and after cyclic pre-stressing 0.25 0.2

vr

0.15 0.1 0.05 0 0

1

2

3

4

5

6

7

Si69 (pphr)

vr

vr prestress

Figure 6. Effect of cyclic pre-stressing (10 cycles at 10MPa) on volume fraction of rubber in the swollen gel of silica-filled vulcanized NR containing different amounts of coupling agent, Si69 (TESPT) – (Azemi & Che Mohd 2013).

63


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Influence of TESPT on Tear Strength

cause the orientation of filler structure and hence the strength anisotropy was necessary for the occurrence of knotty tearing. Figure 10 indicates that 5 pphr appears to be the optimum quantity of coupling agent to produce high tearing energy over the whole range of tear rates. At 10 pphr of TESPT, the tearing energy decreased particularly at the fast rate. This might be attributed to the tightening of network structure at the rubber-filler interface that might interfere with the development of strength anisotropy. Silica-filled NR gave higher tearing energy than that of black-filled NR. Without coupling agent, tearing energy of silica-filled NR was lower than that of black-filled NR.

Figure 7 shows the influence of coupling agent on the tearing energy of silica-filled vulcanized NR. Without the coupling agent, the tearing strength of silica-filled vulcanized NR was relatively low, particularly at the low tear rates. In the absence of coupling agent, knotty tearing was not produced. Instead, the crack propagated in a steady (smooth) manner, and the tearing energy was strongly dependent on the tear rate. The tearing strength increased with increasing tear rate since the energy dissipation increased with the rate as well. However, in the presence of coupling agent knotty tearing was produced. The tearing energy was about a factor of ten higher than that without coupling agent in particular at low tear rates regions. The results here indicated clearly in the silicafilled vulcanized NR; and coupling agent was essential to induce the strength anisotropy necessary for the occurrence of knotty tearing. Without coupling agent the rubber-filler interaction was very weak that the stress was dissipated before it is high enough to cause the orientation of filler structure. In the presence of coupling agent, the rubber-filler interaction is strong sufficiently to support high stresses to

IInfluence of TESPT on Hysteresis Figure 8 shows that the hysteresis increases steadily with increasing amount of TESPT. Hysteresis or energy dissipation affects a number of physical and mechanical properties such as rolling resistance, skid resistance, damping, tensile and tear strengths. The increase in tensile and tear strengths with increasing TESPT could be partly related to the increase in hysteresis. When hysteresis is high, more energy input is required to do external work.

Tearing energy, T vs rate of silica-filled NR at 23oC

T (kJm2)

1000

100

10 10

100

1000

10000

Rate ( Âľm/s) 0 Si69

2 Si69

5 Si69

10 Si69

HAF

Figure 7. Influence of coupling agent on tearing energy of silica-filled vulcanized NR.

64


AK Noriah and Azemi S.: Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled NR

Hysteresis (6th cycles) versus TESPT 0.10

Hysteresis (J)

0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 0

2

4

6

8

10

TESPT (pphr) (6th cycle). Figure 8. Effect of TESPT on hysteresis

CONCLUSIONS

AKNOWLEDGEMENT

The extent of reinforcement in silica-filled vulcanized natural rubber was affected by the amount of coupling agent TESPT. At 50 pphr of precipitated silica, the hardness increased progressively with increasing amount of TESPT.

The authors would like to thank the Dean of Applied Sciences for the permission to present this paper at the International Polymer Technology Conference and Exhibition (IPTCE ‘13). Date of receipt: May 2017 Date of acceptance: July 2017

There was an optimum level of TESPT to achieve high tensile strength and high tearing energy. This optimum level was at 4 pphr for tensile strength and 5 pphr for tearing energy. In the case of tensile strength, beyond 4 pphr of TESPT the crosslink network becomes tight and tensile strength decreases (Azemi 2014). In the case of tearing energy, without TESPT the tear behaviour was predominantly associated with steady tearing that produced low tearing energy. TESPT was necessary to produce high tearing energy associated with an occurrence of knotty tearing.

REFERENCES Azemi, S 2008, An introduction to polymer science and rubber technology, chap. 2, UPENA. Azemi, S & Said, CMS 2013, ‘Influence of Coupling agent on heat build-up and blowout failure of silica-filled vulcanized natural rubber’, J. Rubb. Research, vol. 16, no. 2, pp. 101–117. Azemi, S 2014, ‘Theory and mechanism of reinforcement in natural rubber’, in Natural rubber materials: composites and nanocomposites, Chap. 3, vol. 2, eds. Thomas et al., Royal Society of Chemistry, UK.

The hysteresis increased with increasing TESPT. This increase in hysteresis was also responsible for the increase in tensile and tear strengths. 65


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Choi, SS & Kim, IS 2002, Filler-polymer interactions in filled polybutadiene compounds’, European Polymer Journal, vol. 38, 1265–1269.

the reinforcement of silica-filled rubber compounds’, ACS Meeting, in paper no. 59, Rhode Island/USA. Park, SJ & Cho, KS 2003, Filler-elastomer interactions:influence of silane coupling agent on crosslink density and thermal stability of silica/rubber composites’, Journal of Colloid and Interface Science, vol. 267, pp. 86–91.

Fröhlich, J, Niedermeier, W & Luginsland, HD 2005, The effect of filler-filler and filler-elastomer interaction on rubber reinforcement’, Composites: Part A, vol. 36, pp. 449–460. Gent, AN, Hartwell, JA & Lee, G 2003, ‘Effect of carbon black on crosslinking’, Rubb. Chem. & Technol., vol. 76, pp. 517–532.

Samsuri, AB & Thomas, AG 1988, ‘Tear behaviour of carbon black-filled rubbers’, in Proc. Int. Rubb. Tech. Conf., Penang.

Gent, AN & Hartwell, JA 2003, ‘Effect of carbon black on crosslinking’, Rubb. Chem. & Technol., vol. 76, pp. 517–532.

Samsuri, AB 1989, ‘Strength of filled rubbers’, PhD thesis, Council of National Academic Awards, London School of Polymer Technology, London.

Greensmith, HW & Thomas, AG 1955, ‘Determination of tear properties’, J. Polym. Sci., vol. 18, pp. 189–200.

Vilgis, TA 2009 et al., Reinforcement of polymer nano-composites, theory, experiments and applications, Chap 1.

Luginsland, HD, Frohlich, J & Wehmeier , A, 2001, ‘In influence of different silanes on

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Assessment of Natural Radioactivity Level and Radiological Index in the Vicinity of Lynas Rare-earth Processing Plants W.M. ZAL U’YUN*, M.W. YII, K. MOHD ASHHAR, M.K. KHAIRUDDIN, I. ABDUL KADIR AND Y. MOHD ABD WAHAB The findings of the study on assessment of natural radioactivity level and radiation hazard parameters in the vicinity of Lynas rare-earth processing plants are reported. This study aims to quantify the environmental levels of natural radionuclides in soil collected in the vicinity of Lynas rare-earth processing plants and thereby to assess potential radiological hazards to the environment. About 31 terrestrial sampling locations were chosen for collection of the soil samples. The activity concentrations of the naturally occurring radioactive material (NORM) members, i.e. 226Ra, 228Ra, 238 U, 232Th and 40K were measured using HpGe gamma spectrometer after reaching 30 days of secular equilibrium with their daughters. The mean activity concentration of 226Ra 228Ra 238U, 232Th and 40K in soil samples were 35 Bq/kg, 62 Bq/kg, 38 Bq/kg, 60 Bq/kg and 245 Bq/kg, respectively. The estimated Raeq and Hex readings due to natural environmental radiation in respectively lower than the recommended value of 370 Bq/kg and unity. Meanwhile, the total air absorbed dosage rate was slightly higher than the estimated average global terrestrial radiation but much lower compared to other regions in Malaysia. The results indicated that the radiation hazard in the vicinity of the Lynas rare-earth processing plants was negligible. Thus, it could be concluded that there were no additional radiation level and no radiological hazard effects to the people living in the surrounding areas. Key words: NORM; radioactivity; radiological; rare-earth processing

Assessment of natural ambient radioactivity and its radiological effects in the environment play an important role to protect the health hazard on the environment and general public due to the radiation (Kasoga et al. 2015). The contribution of ambient radioactivity to the background radiation in the environment is mainly from two prominent natural sources, i.e. high-energy cosmic ray particles from the atmosphere and radioactive nuclides that originated from the earth crust which is present everywhere in the environment, including the human body

(UNSCEAR 2000). The primary source of terrestrial radiation received by humans is of the naturally occurring radioactive material (NORM) associated and deposited with the formation of the earth’s crust such as rocks, soils, ores, minerals, sediment, etc. The NORMs which are derived principally from 40K and the daughters of 238U and 232Th decay series such as radium, radon, actinium, protactinium, lead, and polonium. These progenies first appear in the lithosphere level, deposited on the surface soil before it has been washed and drained through

Waste and Environmental Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor, Malaysia * Corresponding author (e-mail: zaluyun@nuclearmalaysia.gov.my)


ASEAN Journal on Science and Technology for Development, 34(2), 2017

several pathways such as weathering, erosion, fallout, rainwater and human activities into rivers transport and finally ended in the marine environment through estuary (Ahmad-Taufek 2004; Akram et al. 2004). In the terrestrial environment, these radioactive series are present in the soil and soil acts as a medium for transferring radionuclides in air and vegetables (Balakrishnan 2015).

implemented, and the problem can be solved and the potential radiological hazards can be reduced. Study of the background or ambient radioactivity present in natural environmental samples such as vegetation, water, air, and soil provide vital information as they help to monitor the radioactivity levels found in the surroundings and also give an indication of changes in the radiation levels due to human activities (Hu et al. 2010). These studies also help to identify and evaluate the distribution of radionuclides in the area (IAEA 2010). Therefore, the present study is carried out with the primary objective to quantify the environmental levels of natural radionuclides in the soil collected at the vicinity of Lynas rare-earth processing plants and thereby to assess potential radiological hazards to the environment.

These radioactive nuclides release radiation everywhere in our surroundings to which humans are exposed (Kasoga et al. 2015). In other words, although natural radioactivity is present at very low levels almost anywhere in the natural environment, everyone is exposed to it in air, food, and water. These amounts in the air are usually so small and do not constitute a health hazard (Yii et al. 2016). Also, the radiation exposure to the general public is due to unplanned and uncontrolled of human activities (e.g. industrial activities). Thus, uncontrolled activities involving NORM can contribute to ambient radioactivity in the environment, thus unwanted exposure and dispersal pose a risk to human health and the environment. Industrial activities such as oil and gas extraction, coal fired power generation, phosphate industries, zircon/zirconium industry, mining and processing of metals and rare-earth, etc. have been reported as potential sources of elevated naturally occurring radionuclides. The presence of NORM with elevated radionuclides concentrations could be an issue at any stage of an operation from the mineral feed stock, intermediate products, final products and the wastes generated during the process (IAEA 2005). In the past, the issue of NORM and their potential hazards associated with human health and contaminating the environment often raised concerns by the public but now many efforts on such environmental monitoring are

EXPERIMENTAL DETAILS Sampling Area Lynas rare-earth processing plants are situated in Gebeng Industrial Estate, adjacent to the Balok River. The estate lies within the capital city Kuantan in the Pahang state. The study areas were established within 3 km radius surrounding the plant and located within at a Latitude 3.97o to 4.03o North and Longitude 103.34o to 103.42o East (Figure 1). Soil Sample Collection About 31 soil samples were collected at randomly selected sampling points surrounding the Lynas Plants (Figure 1) in May 2014 to September 2015 which involved seven trips of sampling activities. Approximately 1 kg of composite surface soil samples was taken using a coring tool at less than 5 cm depth with 68


W.M. Zal U’yun et al.: Radioactivity Level and Radiological Index―Lynas Rare-earth Processing Plants

Road

Figure 1. Location of the sampling points at the study area.

one-metre square area for each point. Stones, pebbles, vegetation, dried leaves, roots, etc. were cleared and removed from soil samples; then the collected samples were place into HDPE plastic bag, properly labelled and sealed before brought back to the laboratory for further analysis.

progeny before to gamma counting (Dowdall 2002; Yang et al. 2005). Gamma Counting Procedure for gamma counting was summarized from the technical report by Yii et al. (2016). All samples were individually counted using high purity germanium (HPGe) gamma spectrometry system with the p-type detector of 25% relative efficiency for 50 000 seconds. It was calibrated using customized gamma multi-nuclides standard sources comprising of 210Pb, 241Am, 109 Cd, 57Co, 123mTe, 51Cr, 113Sn, 85Sr, 137Cs, 88Y and 60Co in the same counting geometry. A container with the same geometry filled with inert materials counted during the weekend was used to determine the background counts. All measurements were corrected to the density and reference date.

Sample Preparation The collected soil samples were individually weighed, transferred into a steel tray and dried at 105oC in an electric scientific oven for a minimum of 24 hours until a constant weight was achieved. Then, the dried samples were ground to powder form and passed through a 200 mesh sieving machine. Samples were transferred into a 600 ml Marinelli beaker, weighed and sealed with thick PVC tape to inhibit radon gases from escaping (Yii et al. 2016). All samples were then stored for a period in excessive of 30 days (>7 half-live of 222Rn and 220 Rn) to establish secular equilibrium between parents and with their respective radioactive

The activities of 226Ra, 228Ra, 232Th, and 238 U were calculated through their progeny energy peaks i.e. 214Pb and 214Bi for 226Ra, and 69


ASEAN Journal on Science and Technology for Development, 34(2), 2017

U; 228Ac for 228Ra; and 212Pb, 228Ac, and 208Tl for 232Th. Meanwhile, 40K was calculated via directly its energy peak (Yang et al. 2005; El-Reefy et al. 2006). All activity calculations were corrected to the density and sampling date. The minimum detectable activities (MDA) for 226 Ra, 228Ra, 232Th, and 238U were 1 Bq/kg after considering the sample size and counting time and 40K was 5 Bq/kg (Yii et al. 2016).

(ii) External radiation hazard, Hex:

238

To estimate the additional radiological hazard on the people which are daily exposed to the natural gamma radiation from soil, the external radiation hazard, Hex was calculated using the following equation as reported earlier by Yang et al. (2005) and Nabil et al. (2010):

Calculation of Radiological Index

Hex = (AU/370) + (ATh/259) + (AK/4810) ≤ 1

The radiological index consists of several parameters. Among these are:

Where, AU, ATh and AK are the activity concentrations for 238U (226Ra), 232Th and 40 K in Bq/kg, respectively. The values of the indices should be ≤ 1 (Krieger 1981).

(i) R a d i u m e q u i v a l e n t a c t i v i t y R a e q concentration index. Radium equivalent activity concentration index with a symbol of Ra eq is among well known and most widely used to estimate radiation hazard index or radiation hazard parameter or radiological index. In this estimation, the specific activities of radium, thorium, and potassium in different combinations in soil samples were compared, where Raeq is defined as bellows (Beretka & Mathew 1985):

(iii) The total air absorbed dosage rate The total air absorbed dosage rate, D (nGy/hr) due to the mean activity concentrations of 238U, 232Th and 40K in Bq/kg is estimated using equation given by UNSCEAR (2000), Venkidasamy et al. (2011), UNSCEAR (2008) and, Sheela and Shanthi (2016);

Raeq = ARa + 1.43ATh + 0.07AK

D = 0.462AU + 0.604ATh + 0.0417AK

Where, CRa, CTh and CK are the specific activity concentrations for 226Ra (238U), 232 Th and 40K (in Bq/kg), respectively. This equation is based on the estimate that 1 Bq/kg of 226Ra (238U), 259 Bq/kg of 232Th and 4810 Bq/kg of 40K generate the same γ- ray dosage rate (Stranden 1979; Yang et al. 2005; Ahmed 2005). For the nonhazardous, the calculated Raeq should not exceed a maximum value of 370 Bq/kg as reported by UNSCEAR (1982).

Where, AU, ATh and AK are the activity concentrations for 238U (226Ra), 232Th and 40 K in Bq/kg, respectively. Sheela and Shanthi (2016) derived this equation for calculating the total air absorbed dosage rate in air at the height of 1.0 m above from the ground that measured the activity concentrations for uniform distribution of naturally occurring radionuclides in the environmental materials. 70


W.M. Zal U’yun et al.: Radioactivity Level and Radiological Index―Lynas Rare-earth Processing Plants

RESULTS AND DISCUSSION

concentration of 40K significantly exceeded other natural radionuclides. This shows that 40 K is a more abundance radionuclide compared to other radionuclides in the soils (Thabayneh & Jazzar 2012). Furthermore, due to 40K is a highly mobile and easy to dissolve radionuclide, its variation might be due to spreading of widely used industrial materials (fertilizer, chemicals, etc.) at Gebeng industrial area (Yii et al. 2016). Another result showed the activity concentrations of 232Th (228Ra) were higher than 238 U (226Ra) at all studied locations. This was mainly due to the decay property that may play an important role in rapid generating of 228Ra (half-life: 5.75 years) from its parent of 232Th compared to 226Ra with long half-life of 1602 years which decay from 232U (Moore et al. 1995; Krest et al. 1999).

Radioactivity Level of 226Ra, 228Ra, 238U, 232Th and 40K in Soil The results of the activity concentrations (Bq/ kg) of 226Ra, 228Ra, 238U, 232Th and 40K in soil samples at a different location in the study area are presented in Figure 2. The activity concentration of 226Ra in soil samples ranges from 8.7 Bq/kg to 95.4 Bq/kg. For 228Ra found to be in the range of 6.6 Bq/kg to 134.0 Bq/kg. The activity concentration of 238U and 232Th varied from 8.7 Bq/kg to 106.0 Bq/kg and 6.2 Bq/kg to 130.0 Bq/kg, respectively. Meanwhile, the activity concentration of 40K in soil found to vary from 10.6 Bq/kg to 1160.0 Bq/kg. These results showed a broad range of radioactivity level where some locations appeared to be higher. This noticeable difference may be attributed to the geochemical composition and origins of soil types in particular study areas (Dabayneh et al. 2008; Thabayneh & Jazzar 2012). Moreover, the higher values of the activity concentrations belong to soil samples which may be attributed to soil types which were probably radioactiverich granite, phosphate, sandstone, and quartzite (UNSCEAR 1993; UNSCEAR 2002).

Radiological Index The radium equivalent activity concentration index, Ra eq, the external radiation hazard, H ex and the total air absorbed dosage rate, D are summarized in Figure 3. The radium equivalent activity concentration index, Raeq and the external radiation hazard, H ex are radiological index, defined as the radiation hazard index which is used to assess the radiation hazard of the gamma ray due to the present of NORM radionuclides (Yii et al. 2016). Their estimations varied from 19.0 – 335.9 Bq/kg (mean: 139.6 Bq/kg) and 0.05 – 0.94 (mean: 0.39), respectively. The value of Raeq found to be not exceeding a maximum value of 370 Bq/kg as reported by UNSCEAR (1982). Meanwhile, the value of the Hex indices was less than unity (the values of the Hex should be ≤ 1) (Krieger 1981). Thus, these findings reflected negligible radiation hazard in the vicinity of Lynas plants negligible. In other words, there were no additional radiation level and no radiological hazard that may effect the people living in the surrounding areas.

The average activity concentrations of 226Ra measured in the present study were comparable to the value reported for offsite Lynas Plant sampling stations during the pre-operational as well as the value reported for worldwide and other countries such as China, Japan, India as summarized in Table 1. Thorium-232 (232Th) found to be higher average values compared to Thailand, China, Japan and world values. The high variability of result attributed mainly to the typical concentration of the radioactive materials in soil, especially in Malaysian soil (Ismail 2009). Meanwhile, activity concentration of 40K in the soil at the present study found to be far lower than other countries. Observation revealed that the measured activity 71


226

Ra

228

Ra

238

U

232

Th

40

K

Figure 2. Soil radioactivity level of 226Ra, 228Ra, 238U, 232Th and 40K in the vicinity of Lynas plant.

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W.M. Zal U’yun et al.: Radioactivity Level and Radiological Index―Lynas Rare-earth Processing Plants

Table 1. Comparison of radioactivity concentrations for 226Ra, 228Ra, 238U, 232Th and 40K in soil. Activity concentration of radionuclide (Bq/kg) Location

Level

226

Ra

228

Ra

238

U

232

Th

K

40

Minimum

9

7

9

6

11

Maximum

95

134

106

130

1160

Average

35

62

38

60

245

Minimum

13

25

Maximum

56

178

Average

26

64

Minimum

12

10

Maximum

57

83

Average

32

69

Pahang (Ismail 2009)

Average

71

88

Peninsular Malaysia (Ismail 2009)

Average

74

98

Minimum

38

49

63

170

Maximum

94

86

110

430

Average

67

66

82

310

Minimum

41

105

75

Maximum

90

516

848

Average

Minimum

20

25

36

Maximum

390

530

2610

Average

94

190

720

This study

Onsite Lynas plant (pre-operational) (Ismail 2009)

Offsite Lynas plant (pre-operational) (Ismail 2009)

Malaysia (UNSCEAR 2000)

Malaysia (Mohsen et al. 2007)

Phuket Island (Chanyotha 2011)

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ASEAN Journal on Science and Technology for Development, 34(2), 2017

Table 1 Cont. Comparison of radioactivity concentrations for 226Ra, 228Ra, 238U, 232Th and 40K in soil. Activity concentration of radionuclide (Bq/kg) Location

Level

226

Ra

228

Ra

238

U

232

Th

K

40

Minimum

11

7

7

Maximum

78

120

712

Average

48

51

230

Minimum

2

1

9

Maximum

440

360

1800

Average

32

41

440

Minimum

20

16

81

Maximum

110

200

1100

Average

59

95

530

Minimum

6

2

15

Maximum

98

88

990

Average

33

28

310

Minimum

7

14

38

Maximum

81

160

760

Average

29

64

400

Worldwide (UNSCEAR 2000)

Average

35

30

400

World average (Yii et al. 2016)

Average

45

33

420

Thailand (UNSCEAR 2000)

China (UNSCEAR 2000)

Hong Kong (UNSCEAR 2000)

Japan (UNSCEAR 2000)

India (UNSCEAR 2000)

74


W.M. Zal U’yun et al.: Radioactivity Level and Radiological Index―Lynas Rare-earth Processing Plants

Figure 3. Profile of radiological index in the vicinity of Lynas plant.

The total air dosage rate for the outdoor environment calculated from the absorbed dosage rate in the study area was found to be varying from 8.6 – 157.1 nGy/h with a mean value of 64.2 nGy/h. This was slightly higher than the estimated average global terrestrial radiation of 55 nGy/h (range: 28 – 120 nGy/h), 57 nGy/h (range: 18 – 93 nGy/h) and 62 nGy/h reported by UNSCEAR (1993), UNSCEAR (2000),] and Hien et al. (2002), respectively. However, this value is much lower compared to the value recorded in Ulu Tiram with a range of 96 – 409 nGy/h (mean: 200 nGy/h) (AbdulRahman 2007), 55 – 130 nGy/h (mean: 92

nGy/h) for Peninsular Malaysia (UNSCEAR 2000), and 2 – 100 nGy/h (mean: 77 nGy/h) for Thailand (UNSCEAR 2000). The radiological index or radiation hazard parameters at some locations in the study area slightly exceeded the UNSCEAR average range but lower than Peninsular Malaysia might be due to natural occurrence of a relatively high activity concentration of natural radionuclides in the soil at particular locations. Usually, they were attributed to soil types which probably contained natural radioactive-rich minerals such as granite, monazite, quartzite, etc.

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ASEAN Journal on Science and Technology for Development, 34(2), 2017

CONCLUSIONS

REFERENCES Abdul-Rahman, AT & Ramli, AT 2007, ‘Radioactivity levels of 238U and 232Th, the α and β activities and associated dose rates from surface soil in Ulu Tiram, Malaysia’, J. Radioanal. Nucl. Chem., vol. 273, pp. 653–657.

The activity concentration level of 226Ra, 228Ra, 238 U, 232Th and 40K measured in the 31 soil samples collected from the vicinity of Lynas rare-earth processing plant were the broad range where some small locations appeared to be higher. These relatively higher values and noticeable difference in some locations might be attributed to the geochemical composition and origins of soil types in particular study areas. Thus, the impacts of these natural radionuclides and the corresponding additional external radiation if any, exposure to the public were almost negligible. Consequently, the measured levels of these natural radionuclides confirmed that there were no hazard effects on the people residing in the vicinity of the Lynas Plant. Apart from that, the finding of this study could contribute to the setting up of a reference level for studies about natural radioactivity in the soil samples of this region in future.

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AKNOWLEDGEMENT

Balakrishnan, D, Umadevi, AG, Abraham, JP, JoJo, PJ, Harikumar, M & Radhakrishnan, S 2015, ‘Assessment of natural radioactivity level and radiation hazard parameters in the terrestrial environment of Eloor Island, Kerala’, Int. J. Fundam. Physic. Sci., vol. 5, no. 2, pp. 38–42.

The authors would like to express their special appreciation to the Ministry of Science, Technology and Innovation for providing research funding under the ScienceFund research grant (06-03-01-SF0189). Special thanks is also commited to the Pahang State Development Corporation for assisting in the execution of this project at Gebeng Industrial Estate. The authors are also thankful to the staff for their kind co-operation and support in implementation this project.

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Date of receipt: April 2017 Date of acceptance: July 2017

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Venkidasamy, R, Pachamuthu, R, Govindasamy, S, Venkatasubramanian, M & Velladurai, P

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Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM Using Unidirectional High-performance IO Standard B. DAS* AND M.F.L. ABDULLAH The distributed dual-port RAM offers the high-speed data rate transmission for different memory access modes such as: busy mode; interrupt mode; JTAG mode; master mode; slave mode; and sleep mode, at high-frequency operation. The execution of these modes at high-frequency operation increases the on-chip temperature of distributed dual-port RAM. It might short the distributed dual-port RAM forever. Currently, different techniques have been reported, but significant on-chip temperature consumption is not reduced for distributed dual-port RAM. In this paper, the thermalefficient design for distributed dual-port RAM was achieved using IO standard technique. The distributed dual-port RAM was designed using different IO standards such as; LVTTL IO standard and Mobile_DDR IO standard. It was determined that distributed dual-port RAM was operated at 625 MHz high-frequency operation for busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode using LVTTL IO standard and Mobile_DDR IO standard. It was observed that for busy mode 53%, for interrupt mode 61%, for JTAG mode 68%, for master mode 62%, for slave mode 59%, and for sleep mode 76% temperature was reduced when distributed dual-port RAM was designed using Mobile_DDR IO standard compared to LVTTL IO standard. The designed distributed dual-port RAM using Mobile_DDR IO standard offered the thermal efficient design solution for different memory access modes at high-frequency data rate transmission that provided the low on-chip temperature consumption. The developed distributed dual-port RAM will be helpful to produce green computing devices. Key words: Distributed dual-port RAM; high-range IO standard; memory access modes; random access memory (RAM); thermal efficient; UltraScaleTM field-programmable gate array

The distributed Memory Generator (DMG) in Xilinx Filed Programming Gate Array core creates the memory out of LUT RAM. This DMG provides the different memory access such as; Read only memory (ROM), Single-Port read access memory (RAM), Dual-port read access memory (RAM). Distributed dual-port RAM in DGM is synchronous with to the clock (CLK) and their read operation can be asynchronous or synchronous concerning either of the two clocks

(CLK or QDPO_CLK). In distributed dual-port RAM in DGM the address, data registers, and resets and clock enables and are optional. It has been defined in Xilink Inc. (2015) that for DGM the maximum frequencies (Fmax) is required for the configuring the memory. The different Fmax for various memory access in defined as; for single-port RAM the memory size is 32×16 at 625 MHz, for Dual port RAM size is 32×16 at 625 MHz. It is discussed in Atmel Corporation

Faculty of Electrical and Electronic Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia * Corresponding author (e-mail: engr.bhagwandas@hotmail.com)


ASEAN Journal on Science and Technology for Development, 34(2), 2017

(2007) that temperature range for distributed dual-port RAM in DGM is varied from –55°C to +125°C depends upon the Fmax used for a specific operation. It also demonstrated in Xilink Inc. (2015) distributed dual-port RAM in DGM there are a different mode of operation such as; busy, interrupt, JTAG, master, slave, and sleep mode. It is also revealed in Xilink (2015) that the core voltage of distributed dual-port RAM in DGM is varied from 1.8 V to 5 V using default IO standard of transistortransistor logic (TTL). It is observed by Das et al. (2016) and Abdullah (2015) that different electronic device, when operated at maximum frequencies, the device temperature increase and this may haul the operation of the electronic devices and may cause the permanent damage to the device. In the case of distributed dualport RAM in DGM, it is very much important to investigate and control the behaviour of temperature variation for distributed dual-port RAM in DGM, when operated in different modes at Fmax of 625 MHz. It has been observed that for distributed dual-port RAM in DGM, the temperature variation for different modes is varied from –55°C to +125°C. This temperature range can be increased for various operation when operated at Fmax of 625 MHz. There are several techniques utilized to control the temperature of electronic devices such as: optical transmitter (Das et al. 2016); video decoders (Bonatto 2011); filters (Pandey et al. 2016). These techniques include, clock gating, voltage scaling, variable frequency, etc. However, each technique has its own advantages and disadvantages. It has been demonstrated by Das et al. (2016), Electronic Industry Alliance (2017), and Xilinx Inc. (2016) that for different variation in suitable IO standard can demonstrate the ability of temperature control of the device by varying the core voltage of field-programmable gate array (FPGA), the

core operating voltage of the device and IO standard voltage selected for the particular device depends on the device configuration. In this paper, the thermal efficient design is demonstrated for distributed dual-port RAM in DGM using high-performance IO standard via UltraScaleTM FPGA. The high-performance IO standard is selected based on the criteria of core voltage of FPGA, and operating voltage of for distributed dual-port RAM in DGM. METHODOLOGY Thermal efficient design for distributed dualport RAM in DGM using high-performance IO standard was designed using different design steps as demonstrated in Figure 1. In the first design step for distributed dual-port RAM in DGM was designed using Vivado® design suite via VHDL coding by defining the different parameters and configuration for distributed dual-port RAM in DGM. In the second design step, the VHDL based on distributed dual-port RAM in DGM was designed using highperformance IO standard. The IO standard was selected based upon the core voltage of FPGA, an operating voltage for distributed dual-port RAM in DGM. In the third design step, the VHDL-based on distributed dual-port RAM in DGM using high-performance IO standard was tested at maximum frequency operation for different mode of operation for distributed dualport RAM in DGM to analyze the performance of the designed thermal efficient for distributed dual-port RAM in DGM. In the last step, the IO standard that had less temperature recording for distributed dual-port RAM in DGM for the different mode of operation was considered as a thermal efficient design for distributed dual-port RAM in DGM. In the next sub-sections, each design step discussed above is detailed. 80


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

Design of the Distributed Dual-Port RAM in DGM in Xilinx Vivado

Thermal analysia of Design of the Distributed Dual-Port RAM using IO Standard

Design of the Distributed Dual-Port RAM using IO Standard

Thermal Efficient design of Design of the Distributed DualPort RAM

Figure 1. Design steps to developing the thermal-efficient design for distributed dual-port RAM in DGM.

A. Design Step 1. VHDL-based Distributed Dual-port Ram in DGM

Table 1 describes the parameters for distributed dual-port RAM. It is illustrated in

The distributed dual-port RAM in DGM was designed in Xilinx VivadoÂŽ Suite using VHDL. The schematic design of distributed dual-port RAM in DGM is shown in Figure 2.

Table 1 that memory depth is of 64 bit and data width is 16 bit for dual port RAM. The port configuration was defined as input was registered and output was non-registered with input clock enabled. The distributed dual-port

The distributed dual-port RAM in DGM in Figure 2 is designed using different parameters as illustrated in Table 1.

RAM was designed using pin configuration that was mentioned in Table 2.

Figure 2. Schematic design of distributed dual-port RAM in DGM via VHDL.

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Table 1. Protocol parameters for distributed dual-port RAM. Memory configuration Depth

64

Data width

16

Memory type

Dual-port RAM Port configuration

Input option

Registered

Input clock

Enabled

Dual-port address

Registered

Input option

Non-registered

Table 2. Port description for designing the Distributed dual-port Ram (Xilinx Inc. 2015) Pin configuration d[p:0]

IO direction

Details

Input data

The input was written into the memory for dual-port RAMs.

a[n:0]

Input address

On dual-port memories, it defined memory location written to, and memory location read out on the SPO[P:0] outputs.

dpra[n:0]

Input

Dual port RAMs and defined memory location read out on the DPO[P:0] outputs.

spo[p:0]

Output

Non-registered single-port output bus. Non-registered data output bus for ROMs and single-port RAMs. One of two non-registered output buses on dual-port RAMs.

dpo[p:0]

Output

Non-registered dual/simple dual-port output bus. One of the non-registered data output buses for dual-port and simple dual-port RAMs. Data stored at the address location specified by DPRA[N:0] appears at this port.

Output qdpo[p:0]

Registered dual/simple dual-port output bus. One of two registered output buses on dual-port and simple dual-port RAMs.

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Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

Table 2 cont. Port description for designing the Distributed dual-port Ram (Xilinx Inc. 2015) Pin configuration clk

IO direction

Details

Input

On dual-port RAMs, signal was the write clock and registered clock for single-port input and output registers.

qdpo_clk

Input

On dual-port RAMs, signal was the write clock and register clock for dual-port and simple dual-port RAM input and output registers.

we

Input

Write enabled.

i_ce

Input

Input clock enabled. Signal was present for RAMs which had registered inputs. The clock enabled controls input data register, address registered and WE register.

It was defined that distributed dual-port Ram using VHDL design was operated at Fmax of 625 MHz for different memory access defined as: busy; interrupt; JTAG; master; slave; and sleep mode. It was also revealed (Xiuyuan 2017; Kumar et al. 2015) that the core voltage of distributed dual-port RAM in DGM was varied from 1.8 V to 5 V using default IO standard of transistor-transistor logic (TTL). It was discussed that for different memory access defined as: busy; interrupt; JTAG, master; slave; and sleep mode, the temperature was varied in between –55°C to +125°C depended upon the Fmax. The proposed IO standard technique offered the less temperature variation for IO standard-based distributed dual-port RAM using VHDL design was operated at Fmax of 625 MHz for different memory access defined as: busy; interrupt; JTAG; master; slave, and sleep mode.

interrupt; JTAG, master; slave; and sleep mode was observed at Fmax of 625 MHz using distributed dual-port RAM using VHDL design and IO standard-based distributed dual-port RAM using VHDL design.

Next, the discussion of IO standard-based distributed dual-port RAM using VHDL design is demonstrated. Subsequently thermal analysis for different memory access defined as: busy;

Virtex® UltraScale™ FPGA support many IO standard and a long list is available in (Electricity Industry Alliance (2017)). In this research, authors have selected the

B. Design Step 2: IO standard-based Distributed Dual-port RAM In UltraScale™ FPGA an I/O tile was defined as I/O buffers, I/O logics and I/O delays. Each IOB contained both input and output logic and IO drivers. These drivers could be configured to various I/O standards (Electricity Industry Alliance 2017). The IO standard based schematic diagram of distributed dualport RAM demonstrated using Figure 3. It is defined in Figure 3 that device configuration was changed by adding the IO standard and its related operating voltage in VHDL-based distributed dual-port RAM.

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ASEAN Journal on Science and Technology for Development, 34(2), 2017

Figure 3. Schematic design of IO-based distributed dual-port RAM in DGM via VHDL.

unidirectional IO standards that meet the requirements for distributed dual-port RAM in DGM via VHDL. These IO standards are specified in the Electronic Industry Alliance JEDEC (2017). The reason for selecting the unidirectional IO standard for distributed dual-port RAM in DGM via VHDL is that unidirectional offers the program in simple mode without handshaking, and secondly the unidirectional IO standards offers the highrange (HR) IO standard that is suitable for distributed dual-port RAM in DGM via VHDL because for distributed dual-port RAM in DGM via VHDL for different memory access modes at Fmax of 625 MHz, the temperature becomes very high.

Double Data RAM (Mobile_DDR (Low-power DDR); and many more. These unidirectional IO standards are further divided in to high range (HR) and high performance (HP) category. It was already discussed in the above discussion that for distributed dual-port RAM, the HR IO standard was required in order to reduce the temperature for different memory access modes. The above unidirectional HR IO standards for distributed dual-port RAM were categorized as: LVTTL which were HR IO standard, and mobile_DDR. (1) Low Voltage Transistor —Transistor Logic (LVTTL) LVTTL is an IO standard for 3.3 V application that uses a single-ended CMOS input buffer and a push-pull output buffer at 3.3 V output source voltage (VCCO). The syntax for changing the IO standards from default to user defined IO standards (LVTTL) is:

There are different types of unidirectional IO standards are which available such as: low voltage transistor transistor logic (LVTTL); low voltage complementary metal-oxide semiconductors (LVCMOS); low-voltage digitally controlled impedance (LVDCI); high-speed low-voltage digitally controlled impedance (HSLVDCI); high-speed transceiver logic (HSTL); high speed unterminated logic (HSUL); pseudo open drain (POD); Mobile

84

a) Attribute IOSTANDARD : string; Attribute IOSTANDARD of IDIOA0 : label is- “LVDCI_15”;


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

C. Design Step 3: Performance Analysis of Distributed Dual-port RAM Using Proposed IO standard Technique

b) Attribute IOSTANDARD : string; Attribute IOSTANDARD of IDIOA0 : label is- “LVTTL_33”;

The thermal performance analysis for the designed distributed dual-port RAM was observed for Fmax of 625 MHz for different memory access mode such as: busy; interrupt; JTAG; master; slave; and sleep mode. This thermal analysis was demonstrated for IO standard based VHDL-based distributed dualport RAM. The thermal analysis is executed using on-chip device temperature for different operations.

(2) Mobile Double Data RAM (MOBILE_ DDR) The mobile_DDR IO standard is for DDR memory buses. Mobile_DDR is defined by the JEDEC I/O standard JESD209A. It is a 1.8 V single-ended I/O standard that eliminates the need for VREF and VTT voltage supplies. The syntax for changing the IO standards from default to user defined mobile_DDR IO standard is:

(1) Thermal Analysis of Distributed dualport Ram for Fmax of 625 MHz via LVTTL IO standard

a) Attribute IOSTANDARD : string; Attribute IOSTANDARD of IDIOA0 : label is- “LVDCI_15”;

The performance of the distributed dual-port RAM is analyzed for Fmax of 625 MHz for LVTTL IO standard by measuring the onchip device temperature for different memory access mode such as: busy; interrupt; JTAG, master; slave; and sleep mode. The LVTTL was configured for the reference voltage of 3.3 V. Therefore the LVTTL syntax would be changed to LVTTL_33. The on-chip device temperature was measured concerning specific mode of operation of distributed dual-port RAM. The on-chip device temperature was measured regarding different mode of operation such as: busy; interrupt; JTAG; master; slave; and sleep mode of distributed dual-port RAM at Fmax of 625 MHz using LVTTL IO standard. Table 3 defines the on-chip device temperature which was measured concerning different mode of operation such as: busy; interrupt; JTAG; master; slave; and sleep mode of distributed dual-port RAm at Fmax of 625 MHz using LVTTL IO standard.

b) Attribute IOSTANDARD : string; Attribute IOSTANDARD of IDIOA0 : label is- “MOBILE_DDR”;

It was discussed earlier that for distributed dual-port RAM using VHDL design is operated at Fmax of 625 MHz for different memory access such as: busy; interrupt; JTAG; master; slave; and sleep mode and the port voltage varied from 1.8 V to 5 V. It was also discussed that for different memory access such as: busy; interrupt; JTAG, master; slave; and sleep mode the temperature varied between –55°C to +125°C which depended upon the Fmax. Also thermal analysis for different memory access such as: busy; interrupt; JTAG, master; slave; and sleep mode for distributed dual-port RAM is analyzed. This thermal analysis was demonstrated by observing the temperature of different memory access modes such as: busy; interrupt; JTAG; master; slave;, and sleep mode for Distributed dual-port Ram and IO standard based distributed dual-port RAM. 85


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Table 3. Thermal analysis for distributed dual-port RAM using LVTTL IO standard. Mode of Operation of distributed dual-port RAM

Temperature of device observed for mode of operation of distributed dual-port RAM in ºC

Busy mode

45ºC

Interrupt mode

65ºC

JTAG mode

75ºC

Master mode

40ºC

Slave mode

42ºC

Sleep mode

30ºC

the different mode of operation are also shown in Figure 4.

Table 3 defines the temperature of distributed dual-port RAM for specific RAM operation at 625 MHz frequency using LVTTL IO standard. It is illustrated in Table 3 that for distributed dual-port RAM using LVTTL IO standard for busy mode 45ºC device temperature was recorded, for interrupt mode in which external input was responded and the device temperature was recorded as 65ºC. For JTAG mode the device temperature was high 75ºC because the transmitter and receiver synchronization, for master mode 40ºC device temperature was recorded, and for slave mode 42ºC device temperature was observed, the reason for less temperature was that slave mode was slow in response and bus speed for slave mode was also slow, so it consumes less temperature compared to master mode. Finally, in the sleep mode, in which no processing is observed the temperature recorded is of 30ºC. The temperature observed for distributed dualport RAM for specific RAM operation at 625 MHz frequency using LVTTL IO standard for

Figure 4 demonstrates the on-chip temperature consumption for distributed dualport RAM using LVTTL IO standard. It could be observed that when distributed dual-port RAM was operated in JTAG more the thermal consumption for distributed dual-port RAM was very high compared to sleep, slave, interrupt and busy mode. The thermal analysis for distributed dualport RAM is shown in Figure 5 for all memory operations such as: JTAG; sleep; slave; interrupt and busy mode. Figure 5 defines that total onchip temperature consumption for different modes when distributed dual-port RAM was designed using LVTTL IO standard. It was also defined that when distributed dual-port RAM was operated using JTAG mode total on-chip temperature consumption was 25%. For interrupt mode the on-chip temperature 86


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

Mode of operation distributed dualport RAM

On-chip temperature consumption distributed dual-port RAM using LVTTL IO standard

Sleep mode Slave mode Master mode JTAG mode Interrupt mode Busy mode

Tempraure (oC)

Figure 4. On-chip temperature consumption distributed dual-port RAM using LVTTL IO standard. Thermal analysis for distributed dual-port RAM using LVTTL IO standard

Busy mode

Interrupt mode

JTAG mode

Master mode

Slave mode

Sleep mode

Figure 5. Thermal analysis for distributed dual-port RAM using LVTTL IO standard.

consumption was 22%, for busy mode the on-

RAM was designed using LVTTL IO standard the on-chip temperature recorded was 10%.

chip temperature consumption recorded was 15%. For master and slave mode the on-chip

In the next section, the thermal analysis for distributed dual-port RAM using Mobile_DDR IO standard is discussed.

temperature consumption it was 14%. Finally for sleep mode, when distributed dual-port 87


ASEAN Journal on Science and Technology for Development, 34(2), 2017

(2) Thermal Analysis of distributed dual-port RAM for Fmax of 625 MHz via mobile_DDR IO standard

Table 4 shows the temperature of distributed dual-port RAM for specific RAM operation at 625 MHz frequency using mobile_ DDR IO standard. It is shown in Table 4 that for distributed dual-port RAM using Mobile_DDR IO standard for busy mode 21ºC device temperature was attained, for interrupt mode in which external input was responded and the device temperature was recorded as 65ºC. For JTAG mode the device temperature was high, 25ºC because the transmitter and receiver synchronization, for master mode 14ºC device temperature was recorded, and for slave mode 17ºC device temperature was observed, the reason for less temperature was that slave mode was slow in response and bus speed for slave mode was also slow, so it consumed less temperature compared to the master mode. Finally, in the sleep mode in which no processing was observed the temperature recorded was 7ºC. The temperature observed for distributed dual-port RAM for specific RAM operation at 625 MHz frequency using mobile_DDR IO standard for a different mode of operation is also shown in Figure 5.

The performance of the distributed dualport RAM analyzed for Fmax of 625 MHz for mobile_DDR IO standard by measuring the on-chip device temperature for different memory access mode such as: busy; interrupt; JTAG; master; slave; and sleep mode. The mobile_DDR IO standard is configured for the reference voltage of 1.8 V. Therefore the LVTTL syntax will be changed to mobile_DDR.The onchip device temperature is measured regarding specific mode of operation of distributed dualport RAM. The on-chip device temperature was measured concerning of different mode of operation such as: busy; interrupt; JTAG; master; slave; and sleep mode of distributed dual-port RAM at Fmax of 625 MHz using Mobile_DDR IOStandard. Table 4 defines the on-chip device temperature is measured regarding different mode of operation such as: busy; interrupt; JTAG; master; slave; and sleep mode of distributed dual-port RAM at Fmax of 625 MHz using mobile_DDR IO Standard.

Table 4. Thermal analysis for distributed dual-port RAM using Mobile_DDR IO standard. Mode of operation of distributed dual-port RAM

Temperature of device observed for mode of operation of distributed dual-port RAM in ºC

Busy mode

21ºC

Interrupt mode

25ºC

JTAG mode

24ºC

Master mode

15ºC

Slave mode

17ºC

Sleep mode

7ºC

88


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

temperature consumption was 14%. Finally, for sleep mode, when distributed dual-port RAM was designed using LVTTL IO standard the on-chip temperature recorded was 6%.

Figure 6 demonstrates the on-chip temperature use for distributed dual-port RAM using Mobile_DDR IO standard. It could be observed that when distributed dual-port RAM was operated in JTAG the thermal use for distributed dual-port Ram was very high compared to sleep, slave, interrupt and busy mode.

It could be analyzed that when distributed dual-port RAM was operated at 625 MHz for different memory access modes using LVTTL IO standard the temperature consumption was compared to distributed dual-port RAM was operated at 625 MHz for various memory access modes using Mobile_DDR IO standard. It was interesting to note that the total on-chip temperature analysis between LVTTL IO standard and Mobile_DDR IO standard for distributed dual-port RAM was compared using Figure 4 and Figure 7, respectively. It could be analyzed that temperature consumption of distributed dual-port RAM using Mobile_ DDR IO standard was less compared to the distributed dual-port RAM using LVTTL IO standard. It was observed that major temperature consumption was reduced for

The thermal analysis for distributed dualport Ram is shown in Figure 7 for all memory operations such as: JTAG; sleep; slave; interrupt; and busy mode. Figure 7 defines that total onchip temperature consumption for different modes, when distributed dual-port RAM was designed using Mobile_DDR IO standard. It was defined that when distributed dual-port RAM was operated using JTAG mode total on-chip temperature the consumption was 22%. For interrupt mode the on-chip temperature consumption was 23%, for busy mode the onchip temperature consumption recorded was 19%. For master and slave mode the on-chip

Mode of operation distributed dualdual-port RAM

On-chip temperature consumption distributed dual-port RAM using Mobile_DDR IO standard

Sleep mode Slave mode Master mode JTAG mode Interrupt mode Busy mode

Tempraure (oC)

Figure 6. On-chip temperature consumption distributed dual-port RAM using Mobile_DDR IO standard.

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ASEAN Journal on Science and Technology for Development, 34(2), 2017

Thermal analysis for distributed dual-port RAM using Mobile_DDR IO standard

Busy mode

Interrupt mode

JTAG mode

Master mode

Slave mode

Sleep mode

Figure 7. Thermal analysis for distributed dual-port RAM using Mobile_DDR IO standard.

sleep mode for distributed dual-port RAM using Mobile_DDR IO standard compared to distributed dual-port RAM using LVTTL IO standard. In this section, the thermal analysis was discussed. Next, the results were presented for proposed thermal efficient distributed dualport RAM. It analyzed that proper selection of IO standards may yield reduction in thermal consumption for distributed dual-port RAM.

such as: busy mode; interrupt mode; JTAG mode; master mode; slave mode, and Sleep mode. It was defined that for these memory access modes for distributed dual-port RAM using LVTTL IO standard the temperature consumption recorded for busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode was 45ºC, 65ºC, 75ºC, 40ºC, 42ºC, and 30ºC respectively, as demonstrated in Figure 8. It could also be analyzed that when distributed dual-port RAM was operated at 625 MHz using mobile_DDR IO standard for different memory access modes such as: busy mode; interrupt mode; JTAG mode; master mode; slave mode; and sleep mode, the temperature consumption recorded for distributed dual-port RAM was 21ºC, 25ºC, 24ºC, 15ºC, 17ºC, and 7ºC respectively, as shown in Figure 8.

RESULTS AND DISCUSSION In this paper, thermal efficient design for distributed dual-port RAM was proposed using high range IO standard. The IO standard was selected according to the specification of for distributed dual-port RAM and UltraScale™ FPGA. For distributed dual-port RAM it was tested for 625 MHz maximum frequency using LVTTL IO standard and mobile_DDR IO standard for distributed dual-port RAM. It was illustrated that when distributed dual-port RAM was operated at 625 MHz using LVTTL IO standard for different memory access modes

It is demonstrated in Figure 8 that when distributed dual-port RAM is designed using Mobile_DDR IO standard and LVTTL IO 90


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

80

Thermal analysis for designed distributed dual-port RAM LVTTL IO standard

Temprature in (oC)

70

Mobile-DDR IO standard

60 50 40 30 20 10 0 Busy mode

Interrupt mode

JTAG mode Master mode Slave mode Sleep mode

Memory operation for distributed dual-port RAM

Figure 8. Thermal analysis for designed distributed dual-port RAM using LVTTL IO standard and mobile_DDR IO standard.

standard for the maximum frequency of 625 MHz for busy mode memory access mode, the on-chip temperature is reduced for distributed dual-port RAM which is designed using mobile_DDR IO standard compared to LVTTL IO standard. It was analyzed that distributed dual-port RAM designed using mobile_DDR IO standard and LVTTL IO standard, the temperature was reduced from 45ºC to 21ºC for Mobile_DDR IO standard on the contrary to LVTTL IO standard-based design for distributed dual-port RAM. It was also determined that 53% on-chip temperature consumption was reduced for distributed dual-port RAM using Mobile_DDR IO standard paralleled to LVTTL IO standard.

compared to LVTTL IO standard for distributed dual-port RAM. It was determined that 61% on-chip temperarure consumption was reduced using Mobile_DDR IO standard for distributed dual-port RAM compared to LVTTL IO standard for distributed dual-port RAM. When distributed dual-port RAM was operated at 625 MHZ for JTAG mode of memory access mode using Mobile_DDR IO standard and LVTTL IO standard, the on-chip temperature was reduced from 75ºC to 24ºC, for distributed dual-port RAM using Mobile_DDR IO standard compared to the distributed dual-port RAM using LVTTL IO standard. It was calculate that on-chip temperature consumption of 68% was reduced for JTAG mode for distributed dualport RAM using Mobile_DDR IO standard compared to distributed dual-port RAM using LVTTL IO standard design.

Distributed dual-port RAM, when operated at 625 MHz using Mobile_DDR IO standard and LVTTL IO standard for interrupt mode, the on-chip temperature consumption was reduced from 65ºC to 25ºC using Mobile_DDR IO standard for distributed dual-port RAM

Distributed dual-port RAM using Mobile_ DDR IO standard and LVTTL IO standard was operated at 625 MHz for master mode. It 91


ASEAN Journal on Science and Technology for Development, 34(2), 2017

was observed that temperature consumption fell from 40ºC to 15ºC using Mobile_DDR IO standard compared to LVTTL IO standard. It was determined that 62% temperature reduction was achieved for distributed dualport RAM using Mobile_DDR IO standard. Distributed dual-port RAM using Mobile_ DDR IO standard and LVTTL IO standard is operated at 625 MHz for master mode, It was observed that temperature consumption fell from 40ºC to 15ºC using Mobile_DDR IO standard compared to LVTTL IO standard. It was determined that 62% temperature reduction was achieved for distributed dual-port RAM using mobile_DDR IO standard. Distributed dual-port RAM using Mobile_DDR IO standard and LVTTL IO standard was operated at 625 MHz for master mode, It was observed that temperature consumption fell from 40ºC to 15ºC using Mobile_DDR IO standard compared to LVTTL IO standard. It was determined that 62% temperature reduction was achieved for distributed dual-port RAM using Mobile_DDR IO standard. Similarly, when distributed dualport RAM was operated at 625 MHz for slave mode using mobile_DDR IO standard and LVTTL IO standard, the temperature reduction was attained form 42ºC to 17ºC using Mobile_ DDR IO standard. It was calculated that when distributed dual-port RAM was operated at 625 MHz for slave mode using Mobile_DDR IO standard reduced the 59% temperature consumption compared to the distributed dualport RAM which was operated at 625 MHz for slave mode using LVTTL IO standard .

It was analyzed that for distributed dual-port RAM using Mobile_DDR IO standard, the total temperature reduction achieved was of 76% compared to distributed dual-port RAM using LVTTL IO standard. The proposed thermal efficient design of distributed dual-port RAM using Mobile_ DDR IO standard defined that for memory access modes such as: busy mode; interrupt mode; JTAG mode; master mode; slave mode; and sleep mode, the on-chip temperature consumption was less compared to distributed dual-port RAM using LVTTL IO standard. It was analyzed that for busy mode (53%), for interrupt mode (61%), for JTAG mode (68%), for master mode (62%), for slave mode (59%), and for sleep mode (76%) temperature was reduced, when distributed dual-port RAM was designed using Mobile_DDR IO standard compared to LVTTL IO standard. It was observed that distributed dual-port RAM using Mobile_DDR IO standard had less onchip temperature consumption for busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode memory access modes compared to distributed dual-port RAM using LVTTL IO standard, the reason for the less temperature consumption is that Mobile_DDR IO standard had the operating voltage of 1.8 V and LVTTL IO standard had the operating voltage of 3.3 V. It was also defined that the distributed dual-port RAM could operate from 1.8 V to 3.3 V, and the core voltage of the UltraScale™ FPGA was 1.8 V. When the distributed dual-port RAM was operated at 625 MHz for different memory access mode (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) using LVTTL IO standard, the operating voltage of IO standard was more than

Finally, when distributed dual-port RAM was operated for sleep mode using both IO standard mobile_DDR and LVTTL, the temperature was reduced. It was observed that the temperature was reduced from 30ºC to 7ºC for distributed dual-port RAM using Mobile_ DDR IO standard compared to distributed dual-port RAM using LVTTL IO standard. 92


Bhagwan and Abdullah: Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM

the core voltage of UltraScale™ FPGA and also maximum voltage range of distributed dual-port RAM, due to this leakage current exceeded and the on-chip temperature was increased for the busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode.

provide the thermal efficient design for memory access modes for high-frequency data rate transmission. CONCLUSION AND FUTURE WORK The thermal-efficient design for distributed dual-port RAM using Mobile_DDR IO standard was achieved for existing distributed dual-port RAM. The distributed dual-port RAM was operated at 625 MHz high-frequency operation for different memory access modes (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) using LVTTL IO standard and Mobile_DDR IO standard. It was observed that the temperature for busy mode (53%), interrupt mode (61%), for JTAG mode (68%), master mode (62%), slave mode (59%), and sleep mode (76%) was reduced when distributed dual-port RAM was designed using Mobile_DDR IO standard compared to LVTTL IO standard. It was concluded that the distributed dual-port RAM using Mobile_DDR IO standard could be operated at less temperature for different memory access modes (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) compared to distributed dual-port RAM using LVTTL IO standard for all memory access modes. The designed distributed dual-port RAM using Mobile_DDR IO standard offered the thermal efficient design solution for different memory access modes (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) at high-frequency data rate transmission. The designed distributed dual-port RAM using mobile_DDR IO standard could be utilized for other memory access mode as well. In the future, distributed dual-port RAM could be optimized for more higher frequency than 625 MHz and for additional memory access modes.

It was also observed that distributed dualport RAM for different memory access mode (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) operated at 625 MHz using Mobile_DDR IO standard the operating voltage of IO standard was equal to the core voltage of UltraScale™ FPGA and also fell in minimum voltage range of distributed dual-port RAM, due to this leakage current was very low and the on-chip temperature was also low for busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode compared to on-chip temperature consumption for distributed dualport RAM using LVTTL IO standard. According to Xiuyuan (2017) the temperature consumption for 10.2% while reducing dynamic energy consumption on the L2 cache by 9.5% is achieved. Kumar (2015) has demonstrated energy efficient RAM, but the temperature consumption is limited to 25ºC – 50ºC, which is practically high. It has been demonstrated that the designed distributed dualport RAM which offered the less temperature consumption of 20ºC to 05ºC at high-frequency operation for different memory modes compared to existing work. The developed device offered the high-frequency operation for distributed dual-port RAM for memory access modes (busy mode, interrupt mode, JTAG mode, master mode, slave mode, and sleep mode) at low temperature using Mobile_DDR IO standard. The designed Distributed dual-port Ram using Mobile_DDR IO standard would 93


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AKNOWLEDGEMENT

Das, B, Abdullah, MFL, Shahida, MSN, Bukhsh, Q & Pandey, B 2016, ‘Temperature control of pseudo noise generator-based optical transmitter using airflow and heat sink profile at high speed transceiver logic IO standard’, Journal of Automation and Control Engineering, vol. 4, pp. 28–32.

This work was supported by the Optical Communication Research Group, Faculty of Electrical and Electronic Engineering, Universiti Tun Hussein Onn Malaysia, Malaysia. We are thankful to Faculty of Electrical and Electronic Engineering, Universiti Tun Hussein Onn Malaysia, Malaysia for encouraging us in this work.

Electronic Industry Alliance 2017, IO standards, [Online]. viewed 17 March 2017, <https:// www.coursehero.com>. Kumar, A, Sharma, GK, Kumar, A, Agrawal, T & Srivastava 2015, ‘Design of energy efficient random access memory circuit using stub series terminated logic I/O standard on 28 nm FPGA’, Asian Journal of Science and Technology, vol. 6, no. 8, pp. 1699–1706.

Date of receipt: June 2017 Date of acceptance: July 2017 REFERENCES Abdullah, MFL, Das, B & Shahida, MSN 2015, ‘Temperature regulations of pseudo noise generator based optical transmitter using airflow and heat sink profile’, International Journal of Materials, Mechanics and Manufacturing, vol. 5, pp. 64–67.

Pandey, B, Das, B, Kaur, A & Kumar, T 2016, ‘Performance evaluation of FIR filter after implementation on different FPGA and SOC and its utilization in communication and network’, Wireless Personal Communications, pp. 1–15.

Atmel Corporation 2017, Rad. tolerant high speed 8 Kb × 16 dual port RAM, San Jose, California, United States; viewed 27 April 2017, <www.atmel.com/Images/doc4146. pdf>.

Xilinx Inc. 2015, Distributed memory generator v8.0, in Product guide, Xilinx Inc, San Jose, California, United States; viewed 27 April 2017, <https://www.xilinx.com/support/ documentation/ip_documentation/dist_ mem_gen/v8_0/pg063-dist-mem-gen.pdf>.

Bonatto, AC, Soares, AB & Susin, AA 2011, ‘Multichannel SDRAM controller design for H. 264/AVC video decoder’, in 2011 IEEE VII Southern Conference on Programmable Logic (SPL), pp. 137–142.

Xilinx Inc. 2017, SelectIO resources, in UltraScale™ architecture, Xilinx Inc, San Jose, California, United States; viewed 17 March 2017, <https://www.xilinx. com/support/documentation/user.../ug571ultrascale-selectio.pdf>.

Das, B & Abdullah, MFL 2016, ‘Low power design of high speed communication system using IO standard technique over 28 nm Chip’, IGI Publisher. Das, B, Abdullah, MFL, Shahida, MSN & Chowdhry, B 2016, ‘Energy efficient design of 100 Gb/s optical DPSK transmitter design using UltraScale™ FPGA’, Indian Journal of Science and Technology, vol. 9, pp. 1–7.

Xiuyuan, B 2017, ‘Circuit and architecture codesign of STT-RAM for high performance and low energy’, PhD thesis, University of Pittsburgh. 94


ASEAN J. Sci. Technol. Dev.,  34(2): 95 – 105

Adsorption and Diffusion Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocomposites R. GUNASUNDERI 1, 2*, AND M. R. H. MAS HARIS1 Chitosan entrapped ENR-50 (CTS-t-ENR) biocomposites developed were studied for the absorption and desorption of 2-naphthol in aqueous media. Biocomposites comprising chitosan (CTS) immobilized or trapped in a partially crosslinked ENR (designated as CTS-t-ENR) was prepared by homogenising CTS in ENR-50 latex with curative agents in the presence of acetic acid. It was found that absorption increased with the increase in the initial 2-naphthol concentrations. Chitosan powder was found to be a poor absorbent compared CTS-t-ENR biocomposites. Desorption study revealed that the 2-naphthol diffused slowly in water. The biocomposites exhibited a good slowrelease properties and this was proven by the kinetic study using zero order, first order, Higuchi equation and Kosmeyer Peppas equation. Thus, these biocomposites with a good controlled release and swelling properties could be very useful in agricultural application. Key words: Chitosan; epoxidized natural rubber; slow-release matrices; pasticides

One of the convenient and cheap methods of controlling pests and weeds is by using pesticide which is widely used in the agricultural field. Pesticides are known to create lots of problems in the environment through leaching, runoff, and volatilisation. This issue can be overcome by using a slow release pesticide as slow-release pesticide has been established as vital keys to various environmental problems caused by the obsolete pesticides. With slow-release pesticide, the required amount is lowered, the efficiency of pesticide usage is improved, and environmental pollution problems are practically negligible. One of the main issues in producing or developing slow release pesticide is the utilization of an appropriate biodegradable material for the matrix. Polymer-coated 1

conventional slow-release pesticides have been widely developed lately (Gerstl & Mingelgrin 1998; Sopeña et al. 2009) with chitosan being one of the polymers (Li et al. 2012). Chitosan is a linear polysaccharides of a (1→4)-linked 2-amino-2-deoxy-p-D-glucopyranose obtained from N-deacetylation of chitin which is commonly found in crustacean (Chandra & Rustgi 1998). CTS is known to increase the usage of marine waste due to its non-hazardous biodegradable properties (Dutta et al. 2004). Incorporation of chitosan in a rubber matrix may further extend its capability on variable release behaviour of insecticide due to the double advantages of both entrapments of the polymer and sorption by chitosan. There have been numerous reports on CTS and epoxidized

School of Distance Education, Universiti Sains Malaysia, 11800 Minden, Penang

School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang * Corresponding author (e-mail: rgunasunderi@usm.my) 2


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Processing of Composite with Different Chitosan Loading

natural rubber (ENR-50) biocomposites (Letwattanaseri et al. 2009; Ismail et al. 2011; Riyajan & Sukhlaaied 2013; Raju et al. 2013; Mas & Raju 2014) but till date no reports have been reported on chitosan-rubber composite on its use as the carrier in slow release of pesticides.

A partially crosslinked ENR was prepared by compounding the ingredients as shown in Table 1 (0 phr CTS) using a high-speed homogenizer in a beaker at ambient temperature (27 – 30°C) for 5 min. Then the compounded rubber was cast in a glass mould and set to air dry at ambient temperature for 24 h before placing in an oven at 60°C for an additional 24 h. The resulting material obtained was a partially crosslinked ENR and was designated herein as 0 phr CTSt-ENR (the letter ‘t’ refers the term ‘trapped’). CTS (5.0 g) was added to 100 ml of 2% v/v acetic acid to form the slurry. Then known quantity (2.5, 5, 10, and 15 phr) of this slurry was added to ENR 50 latex and mixed using a high speed homogenizer at ambient temperature (27 – 30°C) for 2 min. Subsequently, the remaining compounding ingredients (Table 1) were added with continuous mixing for another 3 min. The compounded materials were cast in a glass mould and set to air dry at ambient temperature for 24 h before placing in an oven at 60°C for an additional 24 h.

In this backdrop, we report the development of chitosan entrapped in epoxidized natural rubber for the slow release for 2-naphthol (pesticide precursors). The purpose of entrapment of chitosan in ENR-50 was to improvise the absorption and the desorption capacity of 2-naphthol and to stimulate the biodegradation property of ENR-50 to further sustained release. Therefore attempts were made to absorb the 2-Naphthol physically in the composites and to study the release of it as a slow-release matrix in the agricultural field. MATERIALS AND METHODS Materials ENR-50 latex with Mw of 3.8 × 105 Da was supplied by Malaysian Rubber Board, Kuala Lumpur, Malaysia. The actual epoxy content was determined using Bruker Avance-400 NMR spectrometer to be 51.05 %. Chitosan (CTS) with Mw of 105,100 Da and degree deacetylation of about 95% was provided by Advanced Materials Research Centre, Kedah, Malaysia. The other compounding ingredients used were zinc oxide, stearic acid, N-cyclohexyl-2-benzothiazole sulphonamide (CBS), zinc oxide, stearic acid, and sulphur, were all purchased from Bayer Ltd (Malaysia) and used as received. 2-naphthol was purchased from BDH Chemical Ltd England.

Table 1. Formulation of ENR 50-t-CTS biocomposites.

a b

96

Compounding Ingredients

Dry weight (phr)a

ENR-50

100

Chitosanb

0, 2.5, 5, 10 and 15

50% zinc oxide

1.8

50% sulphur

1.5

50% zinc diethyl dithiocarbamate

1.0

50% antioxidant

1.0

Parts per hundred rubber 5% (w/v) chitosan dissolved in acetic acid


Gunasunderi & Mas Haris: Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocompasities

Method for 2-Naphthol AbsorptionDesorption Study

% of absorption = (Co–Ci) × 100% Ci

Absorption experiment. A stock solution of 2-naphthol was prepared by dissolving 700 mg of the compound in 1000 ml of distilled water inside a 1 litre volumetric flask. Then standard solutions containing 300, 400, 500 and 600 mg/l of 2-naphthol were prepared from the stock solution. 0.2 g of each type of biocomposites (prepared from ENR-50 and with different loadings of chitosan: 0, 2.5, 5, 10, and 15 phr) was placed in separate bottles, and 10 ml of a standard solution was added to each bottle. This procedure was repeated for each standard solution. Then the bottles were covered with paraffin film and kept sanding at ambient temperature (25 – 30°C) for 48 h. Subsequently, the resulting biocomposites were isolated using filter paper and placed in an oven set at 40°C to dry for 24 h i.e. until a constant weight was obtained for each sample.

(1)

Where, Co is the initial concentration (mg/l) and Ci is the final concentration (mg/l). % of absorption capacity = (Co–Ci)V × 100% (2) W Where, Co is the initial concentration (mg/l) and Ci is the final concentration (mg/l), V the volume (l) of the solution, and W is the weight (g) of the adsorbent used. Desorption experiment. To investigate desorption of 2-naphthol from the biocomposites following method was carried out. After the absorption took place, the biocomposites were dried and kept. These dried biocomposites (0, 2.5, 5, 10, and 15 phr) were then placed in a beaker containing 50 ml of distilled water and covered with paraffin film for 48 h. Samples were withdrawn after 24 h, and the solution is circulated through a column for three times before analysis. The samples were then placed again in the same solution. After 48 h samples were withdrawn and the solution is circulated again through a column three times before analysis. The removed samples were put in fresh 50 ml distilled water and the solution was analysed after 48 h. Samples were placed in clean distilled water every 48 h. This procedure was repeated until the 2-naphthol was no longer detected. All desorption experiments were performed for three times, and average values were used for all calculations. The 2-naphthol concentration were analysed using the UV spectrometer. The standard solution of the 2-naphthol used was found to exhibit a wavelength at 326 nm. The height of the peak at this wavelength was used throughout for calculating the 2-naphthol concentration.

The solution was analysed using an UV spectrometer. The UV absorbance was measured using an UV/Vis spectrophotometer in 1 cm quartz cells. The absorption spectrum of each sample was determined in the UV region (200–400 nm) by using a Perkin-Elmer Lambda 35 UV/VIS spectrophotometer. The standard solution of the 2-naphthol used was found to exhibit a wavelength at 326 nm. The height of the peak at this wavelength was used throughout for calculating the 2-naphthol concentration. The amount of 2-naphthol disappearing from solution was assumed to be absorbed by sample whereas the amount of 2-naphthol appearing in the solution was the amount of left behind. All absorption experiments were performed for three times, and average values were used for all calculations. The absorption after 48 h was calculated using Equation 1 and 2: 97


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Amount of 2-naphthol release was calculated using Equation 3: The amount of 2-naphtholreleased to the solution Ă&#x2014;100 % amount release = The initial amount of 2-naphthol absorbed

of chitosan increased the overall absorption capacity. This suggested that after a particular loading of chitosan, the maximum absorption was achieved and therefore the number of molecules bound to the adsorbent and the number of free molecules remaind constant even with further chitosan loading.

(3)

Effect of 2-Naphthol Concentration on the Adsorption of 2-Naphtol

RESULTS AND DISCUSSION

Result in Figures 1 and 2 shows that the uptake increased with the increase in the initial 2-naphthol concentrations. It was evident that the absorption was influenced by the initial concentration. It is well-known that with the increase of the concentration, the adsorbed amount increased as long as the binding sites are not saturated. Besides that initial concentration of the 2-naphthol was a significant driving force to overcome the mass transfer resistance of 2-naphthol between the aqueous and solid phase. An increase in the initial concentration enhanced the interaction between the 2-naphthol and the surface of the samples. The enhancement in the absorption process is also related to the increase in the number of collisions between the 2-naphthol molecules and the biocomposites (Hameed & Hakimi 2008). If an absorption process for 2-naphthol uptake was a physical process, the uptake was usually reversible and reliant on the equilibrium between the 2-naphthol concentration in the solution and the 2-naphthol content on the surface of the composite. Hence the process of absorption was also not favourable at low concentration. Increase in 2-naphthol concentration accelerated the diffusion of 2-naphthol molecules from solution to the adsorbent surface due to the increase in driving force of the concentration gradient.

Effect of Chitosan Loading on the Adsorption of 2-Naphtol The effect of chitosan loading on 2-naphthol (700 ppm) absorption by CTS-t-ENR biocomposites was investigated, and the results are presented in Figures 1 and 2. It was found that chitosan powder had the lowest absorption and the absorption capacity compared to 0 phr biocomposites. Therefore it could be said that chitosan was not a good adsorbent for 2-naphthols since chitosan is known to have different capacities to sorb organic compounds. As seen from Figures 1 and 2, generally the amounts of absorption were not considerably affected by chitosan loading. There was only a slight increase in the 2-naphthol absorption with the entrapment of chitosan in the rubber. These were noticeable from the figure and table that at 2.5 phr the absorption and the absorption capacity increased compared to the rubber by itself and increase in the chitosan loading beyond that did not show a significant increase. At a low concentration of 2-naphthol their absorption amount remained almost the same for all biocomposites. Chitosan powder is non-porous and the chitosan entrapped in the rubber matrix showed and increased in pore volume (Figure 2) suggesting that there was more intra-particle surface than the pores in the rubber matrix itself. Hence, entrapment 98


Gunasunderi & Mas Haris: Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocompasities

650.00

450.00

350.00

250.00

150.00

50.00

0 phr

2.5 phr

5 phr

10 phr

15 phr

100 phr

Chitosan loadings Figure 1. Effect of chitosan loading on the adsorption of 2-Naphtol. 300 mg/l 400 mg/l 500 mg/l 600 mg/l 700 mg/l

30

25 Adsorption capacity (mg of 2-naphtol/g of composite)

Amount absorbed (mg/l)

550.00

20

15

10

5

0 0 phr

2.5 phr

5 phr

10 phr

15 phr

100 phr

Chitosan loading Figure 2. Effect of chitosan loading on the adsorption capacity of 2-Naphtol.

99


ASEAN Journal on Science and Technology for Development, 34(2), 2017

The release of 2-naphthol entrapped in the biocomposites could only occur when the water penetrates the network to swell up the biocomposites and forming of wetting pores and followed by dissolution of the 2-naphthol and allowed it to diffuse through the wetting pores and the polymer matrix along the aqueous path to the surface. Finally, the 2-naphthol would diffuse to the bulk solution through the solid/liquid interface. Thus the release of the 2-naphthol was correlated to the swelling nature of the biocomposites which was important in the slow release studies. Overall the release of 2-naphthol followed two-phase processes which was the initial burst release followed by slow and sustained release. The rapid initial desorption of 2-naphthol as a surface phenomenon. Besides that, the initial release could also be related to the swelling of the biocomposites which assist the dynamic activity of the 2-naphthol within the biocomposites. 2-naphthol had poor solubility (0.74 g/l in water) and high hydrophobicity (log K ow in the range of 2.01 â&#x20AC;&#x201C; 2.84). The octanol-water partition coefficient (Kow) is a measure of the equilibrium concentration of a compound between octanol and water that indicates the potential for partitioning into soil organic matter (i.e., a high Kow indicates a compound which will preferentially partition into soil organic matter rather than water). K ow is inversely related to the solubility of a compound in water (Karickhoff et al. 1979). Determined the diffusion of the 2 naphthol and the transfer from solid/liquid interface. The concentration gradient. Therefore low concentration gradients was formed due to the poor solubility of 2-naphthol resulting in slower diffusion and mass transfer. When a pesticide has a high hydrophobicity characteristic, it tends to have a good affinity/interaction with the chitosan which would also result in a slower diffusion

Figure 3 depicts the theoretical value versus the experimental value of 2-naphthol absorption of the CTS-t-ENR biocomposites. These values were calculated using Equation 4 shown below. Based on these data it was very obvious that chitosan contributes to these unpredicted effects to the biocomposites at higher loading (10 and 15 phr). The effect was mainly due to the voids created by CTS shrinkage during the drying process. These voids allowed the CTS to swell to the maximum to fill up the void by absorbing the water which had penetrated through the rubber matrices. However, at low loading, the contribution of chitosan was negligible as the amount of the chitosan presented could be too little. Based on the data presented in it was noticeable that the absorption was not purely dependent on the amount of chitosan loading but also other factors such as solubility. This explained that absorption of any substance was also related to the solubility effect of that substance. aA1-bA2) Theoretical value, Ă&#x2014;100 = Cbiocomposites c

(4)

where, A1 = % of 2-naphthol absorbed by CTS A2 = % of 2-naphthol absorbed by 0phrCTS-t-ENR a = weight in g of rubber in the biocomposites b = weight in g of CTS in the biocomposites c = weight in g of the biocomposites.

Effect of Chitosan Loading on the 2-naphthol Desorption 2-naphthol released from chitosan-ENR-50 composites is shown in Figure 4 respectively. It was obvious from the plots (Figure 4) that the 2-naphthol release increased with chitosan loading. Since chitosan powder adsorption was not good therefore desorption studies were not carried out on it. Desorption studies were conducted with a sample which had highest 2-naphthol adsorption. 100


Gunasunderi & Mas Haris: Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocompasities

30.00

Adsorption capacity (mg of 2-naphtol/g of composite)

25.00

20.00

15.00

10.00 Experimental value

5.00

Theoretical value 0.00 0

2.5

5

7.5

10

12.5

15

Chitosan loading (phr) Figure 3. Experimental value versus theoretical value of copper absorption by CTS-t-ENR biocomposites.

rate. Since 2-naphthol is highly hydrophobicity and poor in solubility both these nature will contribute to a slow release of 2-naphthol from the CTS-t-ENR biocomposites (Gerstl et al. 1998).

further release. Therefore there was a need to replace or release medium every 72 h to prevent saturation and reabsorption from taking place. Once the release medium had been replaced the amount of release for the first 24 h increased. This situation was carried out to mimic a reallife situation in agriculture field. Whereby, the amount of 2-naphthol release would be dependent on the water content in the soil.

Data presented in Figure 5 indicates that the burst release (Teixeira et al. 1990) is also related to the chitosan loading in the rubber matrix. The higher the chitosan loading the release is also higher. This is probably due to the nature of chitosan which swells easily in waters. Thus, it allows the composite to swell and allows the 2-naphthol molecules to diffuse through the free volumes and porous to the surface. Based on Figure 5 it was found that after 72 h the amount of release drops indicated that the amount of 2-naphthol in the release media had saturated and prevented

In order to postulate the kinetics and the mechanism of the 2-naphthol release from the biocomposites, the diffusion data obtained was fitter using kinetic equations such as zeroorder rate (Lobo et al. 2012), first-order rate (Costa & Sousa 2001), Higuchi square root of time (Costa & Sousa 2001) and Ritger-Peppas (Wang et al. 2009). The diffusion data fitted well with zero-order rate equation. It was evident 101


ASEAN Journal on Science and Technology for Development, 34(2), 2017

72 hours 144 hours 216 hours 288 hours 360 hours

40.00

Total amount diffused (ppm)

35.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00 0 phr

2.5 phr

5 phr

10 phr

15 phr

Chitosan loading Figure 4. Effect of chitosan loading on the 2-naphthol desorption. 72 hours

25.00

Amount diffused (ppm)

48 hours 72 hours

20.00 15.00 10.00 5.00 0.00 1st batch

2nd batch

3rd batch

4th batch

5th batch

Figure 5. Effect of changing the medium on the amount of 2-naphthol diffusion.

from figure and table that the plots appeared linear for up to 16% of 2-naphthol release and the regression values were above 0.97. The linear relationship indicated that the rate of the 2-naphthol diffusion of the biocomposites was non-dependent on the amount of 2-naphthol available for diffusion from the biocomposites.

When the diffusion data obtained were fitted using the Higuchi square root equation, it was evident from figure as well as table that a linear relationship was found in all biocomposites and the regression values were 0.98 and above indicating that the 2-naphthol 102


Gunasunderi & Mas Haris: Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocompasities

release process was diffusion controlled. Referring to Table 2 the slope of the Higuchi curve was found to increase with the increase in chitosan content suggesting that the 2-naphthol release was faster in high chitosan loading compared to low loading.

2011). The deviation of n value below indicated that it can also be due to the complexity of the biocomposites system with a high heterogeneity (Angadi et al. 2011). Interpretations obtained from the study of the release of 2-naphthol from the biocomposites suggested that the main driving force for the release of 2-naphthol from the biocomposites was penetration of the release medium. Therefore, upon contact with the water, the water penetrated into the biocomposites via the channels created by the chitosan and the 2-naphthol release might have happed via diffusion through pores formed. When the matrices were placed in water, the biocomposites started to swell due to the nature of chitosan itself. Increasing chitosan content increased in release rate as calculated and shown in Figure 3 and also proven by the Higuchi equation. This is probably due to the increase in total porosity of the biocomposites as shown in SEM (published elsewhere).

When the 2-naphthol diffusion behaviour was calculated by calculating the values of release exponent from the Ritger-Peppas equation, a good fit into the equation was also observed as shown in the r2 values of Table 2. The values of release exponent (n) were found to be a function of polymer content and the values, being <0.45 for all biocomposites indicating that the 2-naphthol release mechanism followed the Fickian diffusion release. This kind of release characteristics could be attributed to the high viscosity of the polymers and increase of strong entanglements bonds between the polymers which increases the diffusion path length of the chitosan as well as greater resistance to erosion by the diffusion medium (UreĂąa-Amate et al.

Table 2. Kinetic mechanism of 2-Naphthol release from CTS-t-ENR biocomposites. Chitosan loading

Zero order

First order

Higuchi

Ritger-peppas

Q = Q0 - k0t

LnQ = Ln(Q0)-k1t

Q = kHt1/2

Q = ktn

(phr)

R2

K0

R2

K1

R2

KH

R2

n

0

0.97

0.079

0.93

0.003

0.99

2.19

0.98

0.071

2.5

0.99

0.131

0.97

0.004

0.98

3.59

0.99

0.099

5

0.99

0.131

0.97

0.003

0.99

3.59

0.99

0.081

10

0.98

0.145

0.95

0.003

0.99

4.02

0.98

0.079

15

0.98

0.94

0.003

0.99

5.07

0.97

0.084

0.182 3

103


ASEAN Journal on Science and Technology for Development, 34(2), 2017

At higher loading of chitosan, the degree of swelling was higher, therefore bigger and more pores were created in the network structure allowing more 2-naphthol to be released. Hence, both the decreased tortuosity and increased porosity had contributed to the higher 2-naphthol release rate in the composite with high chitosan content. Composite with 0 phr had the lower swelling ability and this exhibited smaller and fewer pores in its network which would be more difficult from the 2-naphthol to dissolve and diffuse. Hence the rate of release in 0 phr was prolonged and almost completed within 360 hours. Unlike with chitosan loaded biocomposites, the release continued at a slower rate. Therefore it could be deduced that the composite with higher chitosan loading contributed to higher 2-naphthol release due to its porosity which were the factors determining the rate and the pattern of 2-naphthol release from the biocomposites.

support, PRGS grant no. 1001/PKIMIA/842021. Dr Gunasunderi Raju is also grateful to the Malaysian Rubber Board for the fellowship scheme in pursuing her PhD study. Date of receipt: August 2017 Date of acceptance: September 2017 REFERENCES Angadi, S, Manjeshwar, L & Aminabhavi, T 2011, ‘Stearic acid-coated chitosanbased interpenetrating polymer network microspheres: controlled release characteristics’, Industrial & Engineering Chemistry Research, vol. 50, pp. 4504–4514. Chandra, R & Rustgi, R 1998, ‘Biodegradable polymer’, Progress in Polymer Science, vol. 23, pp. 1273–1335. Costa, P & Sousa Lobo, J 2001, ‘Modeling and comparison of dissolution profiles’, European Journal of Pharmaceutical Sciences, vol. 13, pp. 123–133.

CONCLUSIONS

Dutta, P, Dutta, J & Tripathi, V 2004, ‘Chitin and chitosan:chemistry, property and application’, Journal of Scientific and Industrial Research, vol. 63, pp. 20–31.

It was found that the CTS-t-ENR biocomposites had a better adsorption capacity than chitosan by itself in 2-naphthol. Also, the absorption was influenced by the initial concentration. However, the 2-naphthol release increased with chitosan loading. The diffusion data fitted well with zero-order rate equation indicating that diffusion of 2-naphthol is non-dependent on the amount of 2-naphthol available. The Higuchi equation indicated that the 2-naphthol release process is a diffusion controlled.

Gerstl, Z, Nasser, A & Mingelgrin, U 1998, ‘Controlled release of pesticides into soils from clay−polymer formulations’, Journal of Agricultural and Food Chemistry, vol. 46, no. 9, pp. 3797–3802. Hameed, B & Hakimi, H 2008, ‘Utilization of durian (Durio zibethinus Murray) peel as low cost sorbent for the removal of acid dye from aqueous solutions’, Biochemical Engineering Journal, vol. 39, no. 2, pp. 338–343.

AKNOWLEDGEMENT

Ismail, H, Shaari, S & Othman, N 2011, ‘The effect of chitosan loading on the curing characteristics, mechanical and

The authors would like to thank the Universiti Sains Malaysia for providing the financial 104


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Raju, G, Mas Haris, MA, Rashid, A, Azahari, B & Noorsal, K 2013, ‘Effect of chitosan loading on mechanical properties, water uptake and toluene absorbency of high and low molecular weight ENR50’, Journal of Rubber Research, vol. 16, no. 3, pp. 179–194.

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Riyajan, S-A & Sukhlaaied, W 2013, ‘Effect of chitosan content on gel content of epoxized natural rubber grafted with chitosan in latex form’, Materials Science and Engineering: C, vol. 33, no. 3, pp. 1041–1047.

Letwattanaseri, T, Ichikawa, N, Mizoguchi, T, Ta n a k a , Y & C h i r a c h a n c h a i , S 2009, ‘Epoxidized natural rubber bionanocomposite: a model case of bionanocomposite using nanofibrous chitosan and its consequent functional properties’, Chemistry Letters, vo. 38, no. 8, pp. 798–799.

Sopeña, F, Maqueda, C & Moril, E 2009, ‘Controlled release formulations of herbicides based on micro-encapsulation’, Ciencia e Investigación Agrarian, vo. 35, no. 1, pp. 27–42.

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Teixeira, M, Paterson, W, Dunn, E, Li, Q, Hunter, B & Goosen, M 1990, ‘Assessment of chitosan gels for the controlled release of agrochemicals’, Industrial & Engineering Chemistry Research, vol. 29, no. 7, pp. 1205–1209.

Lobo, F, Aguirre, CD, Souza, P M, Grillo, R, de Melo, N, Rosa, A. et al. 2012, ‘Preparation and characterization of polymeric microparticles used for controlled release of ametryn herbicide’, Herbicides – Properties, Synthesis and Control of Weeds, ed. M. N. Hasaneen, pp. 1–16.

Ureña-Amate, M, Boutarbouch, N, SociasViciana, M & González-Pradas, E 2011, ‘Controlled release of nitrate from hydrotalcite modified formulations’, Applied Clay Science, vol. 52, pp. 368–373. Wang, H.-L, Liu, S. - Q & Zhang, X. -Y 2009, ‘Preparation and application of sustained release microcapsules of potassium ferrate(VI) for dinitro butyl phenol (DNBP) wastewater treatment’, Journal of Hazardous Materials, vol. 169, pp. 448–453.

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ASEAN J. Sci. Technol. Dev.,  34(2): 106 – 118

Preparation and Characterisation of Crosslinked Natural Rubber (SMR CV 60) and Epoxidised Natural Rubber (ENR-50) Blends M. SASITARAN1, S. MANROSHAN2*, C.S. LIM3, B. N. KRISHNA VENI2, S.K. ONG4 AND R. GUNASUNDERI1 In this study, the influence of di(tert-butylperoxyisopropyl)benzene (DTBPIB) on the properties of natural rubber (NR) blend with epoxidized natural rubber (ENR) was determined. Fourier transform infrared spectroscopy with attenuated total reflectance analysis and gel content confirmed crosslinking occurred in the rubber blends in the presence of peroxide DTBPIB percentage. Studies including tensile properties, dynamic mechanical properties, thermogravimetric analysis (TGA) and water absorptivity showed the changes in properties of the crosslinked NR/ENR blends. Tensile properties analysis disclosed the improvements in the modulus at 300% elongation and tensile strength with increasing NR ratios. Dynamic mechanical analysis revealed the blends to be incompatible and immiscible, with ENR showing a more viscous behaviour compared to the polymer blends. Thermal properties improved by blending NR with ENR as the onset temperature of NR/ENR: 50/50 was higher than pure NR by approximately 10oC and ENR by approximately 2oC. Water absorptivity experiment revealed a two-fold reduction in the presence of crosslinking for all blend ratios. Key words: Natural rubber; epoxidized natural rubber; polymer blend; peroxide crosslinking agent

The advancement in polymer research has brought about the idea of blending polymers. Blending is a process of mixing two or more polymers creating a product which has the combined properties of the individual polymers (Notario, Pinto & Rodriguez-Perez 2016; Ramesh 2016). Looking at this, many researchers have diverged their interest from developing novel polymeric compounds through synthesis to blending. Hence, number of studies have been conducted in recent years on blending various polymers which includes

rubber-rubber blend, plastic-plastic blend and rubber-plastic blend (Vinod, Varghese & Kuriakose 2002; Arroyo et al. 2007; Wan Yunus et al. 2013; Notario, Pinto & RodriguezPerez 2016; Ramesh, 2016). Improvement in thermal, physical and mechanical properties are demonstrated by altering the composition and formulation of blends (Park 2001; De et al. 2013; Díaz, Katsarava & Puiggalí 2014; Ramesh 2016). By blending, the technical and economic difficulties faced during the synthesis of new homogenous polymers are

School of Distance Education, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia Rubber Research Institute of Malaysia, Malaysian Rubber Board, 47000 Sg. Buloh, Malaysia 3 School of Pharmacy, International Medical University, 57000 Bukit Jalil, Malaysia 4 Universiti Kuala Lumpur, Malaysian Institute of Chemical and Bioengineering Technology, 78000 Alor Gajah, Melaka, Malaysia * Corresponding author (e-mail: manroshan@lgm.gov.my) 1 2


M. Sasitaran et al.: Preparation and Characterisation of Crosslinked SMR CV 60 and ENR-50) Blends

avoided as this process is more cost effective and time-saving (Arayapranee & Rempel 2007). Therefore, polymer blending has been recognized as the most promising method to generate new material with tailored individual properties (Ulbricht 2006; Mitragotri & Lahann 2009).

Rajasekar et al. 2009). ENR has been known since 1992 and is commercially available since the past decade. Currently, Malaysian Rubber Board is producing two grades of ENR (i.e. ENR 25 and ENR 50) with the trade name EKOPRENA. ENR 50 is chemically modified from 1,4-polyisoprene rubber and has some distinct properties such as low air permeability, oil resistance, and lower wet grip compared to synthetic rubber (Vinod, Varghese & Kuriakose 2002; Gurunathan, Mohanty & Nayak 2015). Thus, blending NR with ENR is bearing interest to improve stiffness, processibility, resilience and minimizing the damping property of polymers (Imbernon & Norvez 2016). However, polymer blending has its drawbacks as well. Blending immiscible polymers can result in phase separation of the product, which requires a additional component as a mediator, such as a crosslinking agent to facilitate an interaction between the phases (Ismail, Nordin, 2002; Imbernon & Norvez 2016).

Malaysia is one of the leading producers of natural rubber (NR). Natural rubber is classified as an elastomer due to the presence of the polyisoprene backbone (Vinod, Varghese & Kuriakose 2002; Khimi & Pickering 2015). NR has been widely used in various applications due to its outstanding properties such as high tensile strength, resilience, toughness and good processing characteristic (Gurunathan, Mohanty & Nayak 2015; Pal & Panwar 2017). However, there are some limitations to NR properties which includes hardness, modulus, and abrasion resistance that need to be improved for it to be utilized in some specific application (Gurunathan, Mohanty & Nayak 2015). Moreover, degradation by heat and ozone, high gas permeability and low oil resistance of NR have limited its applications (Wang et al. 2016). Studies reported that blending NR with ENR can be an effective solution to improve the properties for being used in widespread applications (Arroyo et al. 2007; Gurunathan, Mohanty & Nayak 2015; Wang et al. 2016; Pal & Panwar 2017).

Crosslinking agents react with polymers either by physical and/or chemical means (BenbettaĂŻeb et al. 2016). The incorporation of a crosslinking agent in polymer blending forms three-dimensional network by generating crosslinks, branching & extension of the chains (Pedernera & Sarmoria 1999). Thus, the application of a crosslinking agent in NR blends with ENR might improve strength, stiffness and thermal stability of NR and/or ENR besides restricting water absorptivity of the blend. It is, therefore, the present work aims is to study the blending of Standard Malaysian Rubber (SMR CV 60) with ENR 50, with DTBPIB acting as the crosslinking agent. The resulting blends were characterized for the functional groups, crosslinking degree, tensile properties, thermal stability and water absorptivity.

ENR is produced by modifying NR via epoxidation where the epoxy rings are introduced on the NR backbone and at the same time reduces the number of double bonds (Arroyo et al. 2007). The polarity of the modified polymer depends on the epoxidation level. ENR has been reported to be compatible with other polar polymers (Varghese, KargerKocsis & Gatos, 2003; Guo et al. 2004; 107


ASEAN Journal on Science and Technology for Development, 34(2), 2017

EXPERIMENTAL

prepared by changing the mass ratio of NR to ENR to achieve blend ratio of 0/100, 25/75, 75/25 and 100/0% by weight. Similarly, the above NR/ENR blends were also prepared without DTBPIB.

Materials Malaysian Rubber Board supplied NR grade SMR CV 60 [Mooney viscosity, ML(1+4) 100oC = 60] and ENR (50 mole% epoxidation). The crosslinking agent, DTBPIB, trade name Luperox® F40 (Figure 1) was purchased from Sigma-Aldrich Chemicals, England, whereas Xylene (analytical grade) was obtained from HmbG, Chemicals, Germany.

Determination of Functional Groups Fourier transform infrared spectroscopy with attenuated total reflectance analysis (FTIRATR) was carried out using a Perkin Elmer Spectrum 1000 series spectrophotometer. Thin films of all NR/ENR blend ratios with and without DTBPIB were analysed. The infrared spectra of the samples were recorded in the frequency range of 600 cm-1 to 4000 cm-1.

METHODOLOGY Sample Preparation Blending process was initiated by masticating 20 g of NR using Thermo Haake Polydrive internal mixer, operating at a temperature of 60oC with the rotor speed of 50 rotations per minute (rpm) for 2 min. After masticating the NR, 20 g of ENR 50 was admixed into the mixing chamber. Blending was continued for another 2 min to form NR/ENR: 50/50 blend. The crosslinking agent (DTBPIB) was fixed at 5 phr (parts per hundred rubber). Lastly, DTBPIB was added, and mixing was continued for another additional 6 min. The blends were moulded using compression moulding with a mould of dimension 100 mm x 100 mm x 1 mm, a pressure of 150 kg/cm2 and cured at 160oC for 10 min. The crosslinking temperature used was based on investigations done on peroxides (Thitithammawong, Nakason, Sahakaro & Noordermeer 2007; Thitithammawong, Nakason, Sahakaro & Noordermeer 2007). Cooling was carried out using a cold press at 30oC for 10 min. Other NR/ENR blends were CH3 H 3C

C CH3

0

0

Determination of Crosslinking Degree Gel content analysis was used to determine the crosslinking degree of NR/ENR blends with and without DTBPIB. The thin films of all blend ratios were cut into tiny pieces weighing approximately 0.5 g each and packed in mesh pockets, pre-weighed and labelled. The weight of the mesh pockets with the samples was recorded and the samples were refluxed using xylene in a soxhlet extractor for 24 h. After 24 h the meshes were removed from the roundbottom flask and dried to a constant weight in an oven at 60oC. The weight of samples after extraction was recorded and the percentage gel content was calculated using Equation 1: A

Gel content (%) =

B

×100

(1)

Where, A is the weight of the sample after extraction and B is the initial weight of the sample.

CH3

CH3

C

C 0

CH3

CH3

CH3 0

C

CH3

CH3

Scheme 1. The chemical structure of Luperox® F40 (Mammadov et al. 2012).

108


M. Sasitaran et al.: Preparation and Characterisation of Crosslinked SMR CV 60 and ENR-50) Blends

Determination of Tensile Properties

weight of the samples was recorded and dried to constant weight in an oven at a temperature of 60 oC for 24 h. The percentage of water absorption was calculated using Equation 2:

Tensile test on NR/ENR blends was carried out according to ASTM D638M-98 with a crosshead speed of 50 mm/min and a static load cell of 100 kN using an Instron 4302 series IX, Universal Testing Machine. Each sample’s width and thickness were measured prior to testing. The mean value of at least five specimens for each sample was reported.

Water absorptivity (%) =

m2 - n1 m1

×100

(2)

where, m2 is the weight of the samples before drying and m1 is the weight of the samples after drying.

Determination of Thermal Stability

RESULTS AND DISCUSSION

The thermal stability of the blends was studied using two techniques, namely: dynamic mechanical analysis and thermogravimetric analysis. For dynamic mechanical analysis, the samples were cut into a rectangular shape (10 mm x 40 mm x 1 mm) and placed in the rotating measuring head of a Mettler Toledo DMA 1 analyser under tension mode with an oscillating frequency of 1 Hz. The dynamic storage modulus (E’), loss modulus (E”) and mechanical loss factor (tan δ) were recorded in the temperature range of –100oC to 60oC at the heating rate of 5oC/min. Whereas, thermal decomposition of NR/ENR blends were studied using a Perkin Elmer TGA 7 analyser. The samples were heated from 30oC to 800oC at a rate of 20oC/min under a nitrogen atmosphere with nitrogen flow rate of 20 ml/min. The onset and maximum degradation temperatures were recorded and plotted as a function of time.

Functional Groups The FTIR-ATR spectra of NR/ENR blends with and without DTBPIB are shown in Figure 1. The spectrum of blend NR/ENR: 100/0 [Figure 2(a)] shows strong peaks of unsaturated C=C stretching and out-of-plane C-H rocking at 1635 cm–1 and 1025 cm–1. On the other hand, medium peaks at 1450 cm–1 and 1375 cm–1contribute to -CH2– and -CH3– bending. The intensity of peaks at 1635 cm –1 and 1025 cm–1 reduced drastically with crosslinking due to the radical reaction of DTBPIB with the unsaturated carbons of NR (P. Phinyocheep 2014). Peaks at 2935 cm–1, 2864 cm–1 and 2840 cm–1 attributed to C-H stretching and the peak at 830 cm-1 indicating C-H bending attached to unsaturated carbon (Kochthongrasamee, Prasassarakich & Kiatkamjornwong 2006; Anancharungsuk et al. 2007). This proves that crosslinking has occurred in NR.

Determination of Water Absorptivity The water absorptivity of NR/ENR samples with and without DTBPIB was measured by first cutting the samples to the nearest 1 g and immersing them in distilled water maintained at room temperature for 840 h (35 days). The samples from each blend ratio were removed from the distilled water, gently blotted to dry with tissue paper to remove the excess water present on the surface of the samples. The

Figure 2(b) shows the NR/ENR: 0/100 spectrum with and without crosslinking, respectively. The peaks at 1110 cm–1 and 870 cm–1 indicate the epoxy ring and C-H bending attached to the epoxy ring, (Mas Haris & Raju 2014) whereas, strong peaks at 1499 cm–1 and 1377 cm–1 can be related to -CH2– and -CH3– bending. A short, broad peak of C=C stretching 109


Transmittance (%)

Transmittance (%)

ASEAN Journal on Science and Technology for Development, 34(2), 2017

Wavenumber (cm-1)

Transmittance (%)

Wavenumber (cm-1)

Wavenumber (cm-1)

Figure 1. The FTIR spectra of NR/ENR blends with ratios of 100/0 (a), 0/100 (b) and 50/50 (c).

Crosslinking Degree

and C-H bending attached to unsaturated carbon are also observed at 1663 cm–1 and 830 cm–1. The intensities at 1110 cm–1 and 870 cm–1 which are observed in NR/ENR:0/100 reduced after crosslinking, which might be due to the opening of the epoxy ring forming crosslink bridges. Subsequently, reduction in C=C stretching and out-of-plane C-H suggest that crosslinking has also occurred at the C=C double bond.

Figure 3 shows the effect of NR/ENR blend ratio on the gel content with and without DTBPIB. The solvent (xylene) was observed to dissolve both NR and ENR, and their respective blends without crosslinking as the gel content obtained were almost 0%. However, once crosslinked, the gel content increased. This proved the formation of three-dimensional networks between the chains in the rubbers. NR/ENR: 100/0 with crosslinking showed the highest gel content of 96% whereas NR/ ENR: 0/100 with crosslinking showed the least gel content of 75%. The gel content between chains of NR was higher than between the chains of ENR and this could be due to the percentage of epoxy rings in the ENR forming less crosslinking bridges between the chains compared to the double bonds present in the isoprene of NR.

Figure 1(c) shows the NR/ENR:50/50 spectrum with and without crosslinking. In the presence of crosslinking, the peaks of th epoxy ring at 1080 cm–1 and C-H bending attached to the epoxy ring at 870 cm–1 were observed to reduce drastically. The same was observed for the C=C stretching and C-H bending attached to unsaturated carbon at peaks of 1653 cm–1 and 831 cm–1. From these results, it is evident that crosslinking has taken place in the NR/ ENR blends. 110


Gel Content (%)

M. Sasitaran et al.: Preparation and Characterisation of Crosslinked SMR CV 60 and ENR-50) Blends

NR/ENR Blend Ratios (W/W) Figure 2. The percentage gel content of NR/ENR blends with and without DTBPIB.

Tensile Properties

modulus and strength. This was because NR had more allylic carbon as compared to ENR. Therefore, with the higher amount of allylic carbon, a higher degree of crosslinking might be expected. This was consistent with the gel content results reported earlier.

Tensile modulus, tensile strength, and elongation at break of NR/ENR blends with and without DTBPIB are shown in Figure 3. The tensile modulus [Figure 3(a)] and strength [Figure 3(b)] without crosslinking were independent of the blend ratios. This could be due to the absence of linkages between chains upon which application of minimal force resulted in the stretching of the films. On the other hand, elongation at break (EB) [Figure 3(c)] was reduced with increasing NR loading, due to the carbon-carbon double bonds that are stronger and more constraining upon stretching compared to the epoxy rings of ENR.

The opposite was however observed for elongation at break. Although no significant changes were observed for the blends, changes were observed for the pure polymers with a reduction in EB for ENR (NR/ENR: 0/100) and an increase in the EB for NR (NR/ENR: 100/0). The poorer EB for ENR compared to NR was due to the three-dimensional network formation which limited molecular chain mobility. However, the scission of a much stiffer carbon double bond to form crosslinking could have increased the chain mobility in NR. The results were consistent with the FTIR-ATR and gel content reported earlier.

Upon the introduction of crosslinks, both tensile modulus at 300% elongation (M300) and tensile strength increased for all blend ratios. The crosslinking results in stiffer and stronger blends due to the three-dimensional network formed which limited the molecular chain mobility of the polymer blend. Thus higher force was required to stretch the blend. It was also observed that when the NR loading increased, the blend showed higher tensile

Dynamic Mechanical Analysis The storage (Eâ&#x20AC;&#x2122;) and loss (Eâ&#x20AC;?) moduli of the blends as a function of temperature in the presence of DTBPIB are shown in Figure 4. 111


Non-crosslink Crosslink

Tensile strenght (MPa)

Tensile modulas (MPa)

ASEAN Journal on Science and Technology for Development, 34(2), 2017

Elongation at break (MPa)

NR/ENR blend ratios (W/W)

Non-crosslink Crosslink

NR/ENR blend ratios (W/W)

Non-crosslink Crosslink NR/ENR blend ratios (W/W)

Figure 3. The tensile modulus at 300% elongation (a), tensile strength (b) and elongation at break (c) of NR/ENR blends.

In general, the changes in E’ and E’’ are a direct representation of the intermolecular and intramolecular interactions between polymers. At low temperature, the moduli did not show much change as the deformation was primarily elastic due to the less molecular motion. As the temperature was increased, E’ reduced reaching a minimum with no further changes. On the other hand, E’’ increased reaching a maximum before decreasing. The increase in E’’ was due to Brownian motion and stress relaxation acting together whereas the decrease in E’’ after that was due to the free movement of the molecular segments of the polymer (Sin et al. 2014). From the results in Figure 4, pure polymers (Figure 5 (a and e)) showed a single E’’ peak whereas two E’’ peaks were observed for the blends [Figure 5 (b, c and d)]. The two E’’ peaks show incompatibility between the polymers. However, as the NR content was increased,

the distance between the two peaks reduced. In order to elucidate the results further, tan δ was used (Figure 5). Using the tan δ value versus temperature plot in Figure 5(a), information on glass transition temperature (Tg) and damping were obtained. The Tg was indicated by the number of peaks and from Figure 6 (a), it was evident that both pure polymers (NR and ENR) showed single peaks indicating one Tg value whereas the blends showed two peaks indicating two Tg values. Damping, on the other hand, was observed from the tan δ values. At their respective Tg, ENR showed tan δ of 2 whereas NR showed tan δ of 2.8. As the tan δ was higher for NR, NR showed higher damping compared to ENR at Tg. Blending both polymers resulted in a significant reduction in damping as indicated by the reduced tan δ 112


E, E” (MPa)

E, E” (MPa)

M. Sasitaran et al.: Preparation and Characterisation of Crosslinked SMR CV 60 and ENR-50) Blends

E, E” (MPa)

Temperature (oC)

E, E” (MPa)

Temperature (oC)

Temperature (oC)

E, E” (MPa)

Temperature (oC)

Temperature (oC)

Figure 4. The effect of temperature on the storage (E’) and loss (E”) moduli of NR/ENR blend in the presence of DTBPIB for blend ratios of (a) 0/100, (b) 30/70, (c) 50/50, (d) 70/30, (e) 100/0.

values. Nevertheless, tan δ values of the blends increased with increasing ENR content, and this was associated with the increase in interfacial bonding due to the increased crystallinity of blends (Chandra, Singh & Gupta 1999; Sin et al. 2014).

(ENR/NR:100/0) was double the damping of pure NR (ENR/NR:0/100). The blending of NR to ENR at all blend ratios also resulted in a reduction in damping as the tan δ approached values of pure NR (in the range of 0.08). The higher damping of pure ENR was probably due to the presence of lesser allylic carbons and crosslinks compared to NR resulting in the higher molecular chain mobility.

At room temperature (30oC), a change in the damping behaviour was observed for all blends (Figure 5(b). The damping of pure ENR 113


tan δ

tan δ

ASEAN Journal on Science and Technology for Development, 34(2), 2017

Temperature (oC)

NR/ENR Blend Ratios (W/W)

(a)

(b)

Figure 5. Tan δ of crosslinked NR/ENR blends as a function of temperature (a) and at 30 oC (b).

Thermogravimetric Analysis

ENR. However, the maximum decomposition temperature was slightly lower than pure ENR. In comparison to the NR, ENR showed an increase of 8oC and 10oC in onset and maximum decomposition temperature, respectively. NR exhibits low thermal stability and degrades in the presence of high temperature due to the C=C in the backbone (Piya-Areetham, Rempel & Prasassarakich 2014). This results in NR to be thermally less stable than ENR and blending NR with ENR enhanced the thermal properties of the blends.

The TGA and DTG curves of NR/ENR blends in the presence of DTBPIB are shown in Figure 6. From the thermograms, the information on the onset temperature of degradation and maximum decomposition temperature were obtained, and the results are summarised in Table 1.

Weight % (%)

Derivative Weight % (%/min)

From Table 1, it is evident that blending NR with ENR improved the thermal stability of the blends as the onset temperature of NR/ ENR: 50/50 was higher than for pure NR and

Temperature (oC)

Temperature (oC)

Figure 6. The TGA (a) and DTG spectra (b) of NR/ENR blends in the presence of DTBPIB.

114


M. Sasitaran et al.: Preparation and Characterisation of Crosslinked SMR CV 60 and ENR-50) Blends

Table 1. Onset and maximum decomposition temperature of NR/ENR Blend with DTBPIB. NR/ENR Ratio

Temperature (oC) Onset

Maximum decomposition

0/100

365.4

392.1

50/50

367.2

390.3

100/0

357.5

382.9

Water Absorptivity

blend ratio of 100/0 showed the least water absorptivity owing to the hydrophobic (nonpolar) structure of NR.

Figure 8 shows the water absorptivity by NR/ENR blends with and without DTBPIB, measured for 35 days. In comparison to blends without DTBPIB, the blends with DTBPIB [Figure 8(b)] showed a 50% reduction in water absorptivity. The DTBPIB forms a three-dimensional network which hinders the penetration of water molecules into the network, therefore reducing the water absorptivity of the blends (Abdelmouleh et al. 2007).

CONCLUSION NR and ENR blends were successfully prepared by melt blending method. The FTIR-ATR showed crosslinking which occured not only in the pure polymers but also in the blends. As a result, the percentage gel content of the NR/ENR blends was increased with a higher degree of crosslinking observed for blends with increasing ratio of NR. Similarly, the tensile modulus at 300% elongation and tensile strength of NR/ ENR blends also increased with crosslinking. However, no changes were observed in the

Water Absorptivity (%)

Water Absorptivity (%)

The highest water absorptivity was observed for NR/ENR:0/100 blend ratios, with and without DTBPIB. This was due to the high polarity of ENR which exhibited hydrophilic (polar) nature. A reducing trend in water absorptivity could be seen in the blends with increasing NR ratio. Ultimately NR/ENR

Hour

Hour

Figure 7. The water absorptivity of NR/ENR blends without DTBPIB (a) and with DTBPIB (b).

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elongation at break after crosslinking although a reduction in EB was observed in the absence of crosslinking with increasing NR loading. This was probably due to breaking of C=C bonds to form C-C linkages which were less constraining between NR polymers. Dynamic mechanical analysis revealed the blends which was immiscible due to the presence of two peaks which represented the individual polymers. At room temperature, ENR showed a more viscous behaviour which reduced with increasing NR loading. On the other hand, the thermal properties favoured ENR compared to NR, as NR had more C=C double bonds in the backbone which rendered a lower thermal stability. Therefore, blending ENR with NR improved the thermal properties of the NR/ ENR blend. In the absence of crosslinking, both polymers and their respective blends showed high water absorptivity with higher absorptivity favouring a higher ENR loading due to its polar nature. The introduction of polymer networks through crosslinking significantly reduced the water absorptivity.

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Date of receipt: May 2017 Date of acceptance: October 2017

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Wang, R. et al. 2016, ‘Design, preparation and properties of bio-based elastomer composites aiming at engineering applications’, Composites Science and Technology, Elsevier Ltd, vol. 133, pp. 136–156.

Ulbricht, M 2006, ‘Advanced functional polymer membranes’, Polymer, vol. 47, no. 7, pp. 2217–2262.

118


ASEAN J. Sci. Technol. Dev.,  34(2): 119 – 124

Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients Admitted to a Government Hospital ― A Cohort Study S. SANDASORROOPAN1, K. JUDENIMAL2, AND R. (111) P. DIOSO*3 This study identified the number of reduced and controlled serum cholesterol level among obese patients, and compared diet and exercise in decreasing obesity. A descriptive analytic cohort study was conducted at Kalmunai Base Hospital from May to July 2016. A total of 120 adult subjects were purposively selected to answer the self-administered questionnaire. Central tendencies used frequencies and percentile rankings for data analysis. Around 200 patients confirmed with high cholesterol at the medical ward doing exercise and 500 at medical and surgical clinic having diet therapy were enrolled. However, only 120 were included. Of the 120 patient respondents, 110 were obese, and ten were extremely overweight. In 90 days, combining diet and exercise, it reduced the cholesterol level of 49 participants to ≥ 25mg/dl at a high probability of p = 0.0019. In comparison to diet alone, 33 (27%) decreased their cholesterol level (p = 0.0108), while only exercising reduced cholesterol level (p = 0.010) among 38 (32%) patients. Key words: Cholesterole; cohort study; diet and exercise; nursing; obesity; Sri Lanka

High cholesterol level is one of the many life-threatening conditions in Sri Lanka (Daily Mirror 2015). Decreasing cholesterol is usually done through diet and exercise (Babbie 1998). The purpose of this study deems to promote a healthy lifestyle among the Sri Lankan population. Nowadays, developing health promotion is as important as curing the symptoms itself. The Sri Lankan people are mainly depend on the agricultural-based economy (Jayasinghe 2005). The main food of Sri Lankans are rice, and rice-based foods (Epaarachchi et al., 2002; Jayasinghe 2005). However, in the

recent decades due to the world modernization of changes, it occurred among the Sri Lankan people to adapt industrialization and eat modern food high in cholesterol leading to obesity (Wimalaratana 2011; Epaarachchi et al. 2002). In a more extended period it affects the peoples’ body health and increases the risk factors that lead to increases in cholesterol (Daily Mirror 2015). On account of these issues, this research hopes to: 1. Identify the number of reduced and controlled cholesterol level among Sri Lankan, obese patients and;

Kalmunai Base Hospital, Sri Lanka Batticaloa Teaching Hospital, Sri Lanka 3 Lincoln University College, Jalan SS 6/12, 47301 Petaling Jaya, Malaysia * Corresponding author (e-mail: duke@lincoln.edu.my) 1 2


ASEAN Journal on Science and Technology for Development, 34(2), 2017

2. Compare diet and exercise in decreasing obesity.

the 700 total patients, only 120 fell from the inclusion criteria to answer the self-administered questionnaire. After the 3rd month (July 2016) 10 patients per day were selected to participate in answering the survey questionnaires and 30 minutes per patient spent their time responding.

METHODOLOGY Ethical clearance and approval to conduct this research were primarily obtained from the Research Management Committee of Lincoln University College. The Ministry of Health in the eastern Sri Lanka also permitted to commence the study. Lastly, Kalmunai Base Hospital in Sri Lanka gave permitted to conduct the survey. The patients’ statements, body conditions disease conditions, and names will be maintained anonymous, and the data would not be used for any other purposes. Participants were informed that this was voluntary and that they could withdraw from the study at any time if they wished to do so.

Patients with crutches, diabetic foot ulcers, hypertensive crisis, palpitations, anemia, blood dyscrasia, vertigo, migraines and potential for open heart surgeries were excluded. Besides, patients who would not pursue the intervention (diet and exercise) for 90 days were also eliminated. To validate that the patients adhered to diet and exercise protocols, a procedure guide was used by the authors. This validation would also guide the analysis of the results using central tendencies and t-test.

A descriptive analytic observational cohort study design was employed from May to July 2016. No interventions were conducted during the observation periods. Only checklists and self-administered questionnaire were used to collect the data. The survey questionnaire was not used to evaluate diet and exercise as an intervention but just identified the reduced or controlled serum cholesterol level and compared diet and exercise in reducing obesity.

The estimated prevalence was set at 20%, with 5% margin of error and 95% confidence. Probability findings and one-tailed t-test were used to compare the gaps between evidence of diet and exercise. Statistical Package for Social Sciences Version 21 was used. A descriptive statistics cross-tabulated diet and exercise. RESULTS AND DISCUSSION Of the 120 participants, 84 (70%) were male, and 36 (30%) were female. The single status was 23 (20%) and married was 97 (80%). The majority of the age bracket were 51–55 years (n = 38). The least age bracket were 35–40 years (n = 13). Overall, 92% are obese, and 8% are extremely overweight. Body mass index were calculated using the height in centimeters and weight in kilograms, and the unit of measurement is in cubic millimeters (mm³). Table 1 shows the frequency and percentage characteristics of the respondents.

This study only included patients with ≥ 2 month’s history of cholesterol ≥ 21 years old. Also, only adult obese patients with serum cholesterol ≥ 100mg/dl were selected to participate in this study. Purposive sampling technique was done. Around 200 high cholesterol patients at the medical ward doing exercise and 500 high cholesterol patients at medical and surgical clinics having diet therapy were enrolled. Of 120


Sandasorroopan et al.: Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients

Table 1. Frequency and percentages characteristic of respondent (n = 120). Frequency =n Gender

Male Female

Age

84 36

Percent % 70 30

(35 – 40) y

13

10.83

(41 – 45) y

19

15.83

(46 – 50) y

24

20

(51 – 55) y

38

31.66

(56 – 60) y

26

21.66

Marital status

Married Single

97 23

80 20

BMI

Under weight

Normal

Occupation

Obese Extremely obese

110 10

91.66 8.33

Government Private Self

65 29 26

54.16 24.16 21.66

120

100

Total

Of the 120, 27% (n = 33) used only diet habits, while 38 patient used only exercise (32%) and 49 (41%) patients used both (Figure 1).

Table 3 shows a decrease in cholesterol level between 5 to 10 mg/dl (15.8%), or 11 to 15 mg/dl (11.7%) or ≥ 21 mg/dl (40.8%). Exercise as well could decrease cholesterol level between 11 to 15 mg/dl (5%), or 16 to 20 mg/dl (16.7%) or ≥ 21mg/dl (10%) by exercise alone. A total of 49 patients decreased their cholesterol level ≥ 25 mg/dl by combining diet and exercise (41%). Combining diet and exercise was more probable (p = 0.0019) as compared with diet (p = 0.0108) or exercise (p = 0.010) alone.

Diet and exercise were compared using one-tailed t-test. The result shows a variance of greater than 1.0 (t = 5.994) with a mean score of 38.18182 from the 120, having a deviation of 29.88 (Table 2). There is a big gap between diet and exercise when done separately. 121


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Diet

Exercise Diet and exercise

Figure 1. Percentage of populations doing diet or exercise and diet with exercise.

Table 2. Testing diet and exercise. t-test 5.994

Degrees of

Standard

freedom

deviation

21

29.88

95% Confidence

Mean 38.18182

≤ 0.05

≥ 0.05

24.9337

51.4299

Table 3. Probability findings between diet and exercise. Diet

N=

%

Decreased cholesterol within 5–10mg

19

15.8%

Decreased cholesterol within 11–15mg

14

11.7%

Decreased cholesterol ≥ 21mg

49

40.8%

N=

%

Decreased cholesterol within 11–15mg

6

5.0%

Deceased cholesterol within 16–20mg

20

16.7%

Decreased cholesterol ≥ 21mg

12

10.0%

Diet and Exercise

N=

%

Decreased cholesterol ≥ 25mg

49

41%

Decreased cholesterol ≤ 25mg

0

0

Exercise

122

Mean

27.33

Mean

12.66

Mean

24.05

Standard deviation

15.46

Standard deviation

5.7348

Standard deviation 0

Probability

0.0108

Probability

0.010

Probability

0.0019


Sandasorroopan et al.: Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients

Proper Diet

Most of the respondents were government employees n = 65 (54%). Most government workers in Sri Lanka, were working nearly eight hours per day; therefore they ate more frequently fast foods from restaurants and had no time to do exercise.

Proper diet is done by the appropriate consumption of fat, protein, carbohydrate, vitamins, and minerals in adequate ratio (Ross et al. 2000). Obese patients with high serum cholesterol should eat only 1 cup of rice for breakfast, brunch or lunch with â&#x2030;¤ 80 grams of unfried meat and just fiber and fruits at night without meat (Ross et al. 1996). This study recommends that they should not skip meals, and remove snacks. Also, drinking â&#x2030;Ľ 8 glasses of water daily for those without kidney failure. Increasing the regular intake of fiber every day, and caution should be taken for those with gastrointestinal and absorption problems. Only 1 portion of dairy food products per day is recommended (Nieman et al. 1990). Meat or processed products and pastries are recommended once a week (Moynihan et al. 1996). Lastly, bad fats sources such as butter, margarine, and recycled cooking oils should be removed from the diet (Ross et al. 2000; Ross et al. 1996).

The Sri Lankans were aware about their cholesterol level and had ideas on their diets and exercises. Their interest in diet and exercise was the main problem. However, the patients were very cooperative. Confounding variables were limited to demography such as age, gender, occupation, and marital status, however, did not affect diet, exercise, and diet and exercise. The reduced cholesterol level by diet included the reduced amount of cholesterol intake such as fried foods, beefy meals, and carbonated drinks. It was agreed by Wood et al. (1991) in England that the effects on plasma lipoproteins of a prudent weightreducing diet, can be done without exercise, in overweight men and women. The reduced cholesterol level by exercise is due to morning routines such as jogging, cycling, brisk walking and dancing. Haskell (1986) confirmed that the influence of exercise training on plasma lipids and lipoproteins reduces serum cholesterol.

Proper Exercise Proper exercise of â&#x2030;Ľ 1 hour of running per day for patients without heart problems is recommended (Haskell 1986). It can also be brisk walking, jogging, weight lifting, biking, rock climbing, boxing, swimming, and working out (Crouse et al. 1997). National Education Program (2001) say that proper exercise can decrease serum cholesterol level among obese but should be taken with caution among patients with heart problems or post-open heart surgeries. This study overall recommended proper exercises mainly to prevent co-morbidities of high serum cholesterol from occuring.

RECOMMENDATIONS The findings suggest controlling serum cholesterol level. Decreasing serum cholesterol among obese does not only focus on drug influences but through proper diet and exercise that was proven to reduce the level of cholesterol (Hagan et al. 1986). It is recommended to establish health education centers in every hospital (National Institutes of Health 1998) in Sri Lanka to educate the obese patients about diet and exercise.

Date of receipt: November 2017 Date of acceptance: December 2017 123


ASEAN Journal on Science and Technology for Development, 34(2), 2017

REFERENCES

Adults (Adult Treatment Panel III)], Journal of the American Medical Association, vol. 285, pp. 2486–2497.

Crouse, SF, O’Brien, BC, Grandjean, PW, Lowe, RC, Rohack, JJ & Green, JS 1997, ‘Effects of training and a single session of exercise on lipids and apolipoproteins in hypercholesterolemic men’, Journal of Applied Physiology, vol. 83, pp. 2019–2028.

National Institutes of Health 1998, ‘National Heart, Lung, and Blood Institute: Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults: the evidence report’, Obesity Research, vol. 6, pp. S51–S210.

Daily Mirror 23 June 2015, ‘Sri Lanka at high risk of heart diseases: report’, <http://www. dailymirror.lk/77253/sri-lanka-at-high-riskof-heart-diseases-report>.

Nieman, DC, Haig, JL, Fairchild, KS, De Guia ED, Dizon, GP & Register, UD 1990, ‘Reducing-diet and exercise-training effects on serum lipids and lipoproteins in mildly obese women’, American Journal of Clinical Nutrition, vol. 52, pp. 640–645.

Epaarachchi, R., Jayanetti, S & Weliwita, A 2002, Policies and their implications for the domestic agricultural sector of Sri Lanka: 1995 – 2000, Research Studies: Agricultural Policy Series No. 5, Institute of Policy Studies, Colombo 3, Sri Lanka.

Ross, R, Dagnone, D, Jones, PJ, Smith, H, Paddags, A, Hudson, R & Janssen, I 2000, ‘Reductionin obesity and related comorbid conditionsafter diet-induced weight loss orexercise-induced weight loss in men: a randomized controlled trial’, Annals of Internal Medicine, vol. 133, pp. 92–103.

Hagan, RD, Upton, SJ, Wong, L, Whittam, J & Weinstock, RS 1986, ‘The effects of aerobic conditioning and/or caloric restriction in overweight men and women’, Medicine and Science in Sports and Exercise, vol. 18, no. 1, pp. 87–94.

Ross, R, Rissanen, J, Pedwell, H, Clifford, J & Shragge, P 1996 Influence of diet and exercise on skeletal muscle and visceral adipose tissue in men’, Journal of Applied Physiology, vol. 81, pp. 2445–2455.

Haskell, WL 1986, ‘The influence of exercise training on plasma lipids and lipoproteins in health and disease’, Acta Medical Scandinavian, vol. 711, pp. 25–37.

Wimalaratana, W 2011, Agriculture and rural development in Sri Lanka, Department of Resource Centre. Colombo, University, Colombo Publishing.

Jayasinghe, M 2005, Role of food and agriculture sector in economic development of Sri Lanka: do we stand right in the process of structural transformation? Makandura, Gonawila: Wayamba University of Sri Lanka Publications.

Wood, PD, Stefanick, ML, Williams, PT & Haskell, WL 1991, ‘The effects on plasma lipoproteins of a prudent weight-reducing diet, with or without exercise, in overweight men and women’, New England Journal of Medicine, vol. 325, pp. 461–466.

National Cholesterol Education Program 2001, ‘Experts panel on detection, evaluation, and treatment of high blood cholesterol in adults’ [Summary of the Third Report of the National Cholesterol Education Program, Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in

World Health Organization 1998, Obesity: preventing and managing the global e p i d e m i c , G e n e v a , Wo r l d H e a l t h Organization, Publications. 124


ASEAN J. Sci. Technol. Dev.,  34(2): 125 – 132

Quantitative Analysis of Microcystin-LR in Drinking Water Comparing On-Line Solid Phase Extraction and Direct Injection LC/MS/MS R. MALARVILI, Y.Y. LOW AND A. ZAITON An efficient method for microcystin-LR in drinking water at the sub-ng/l level applying on-line solid phase extraction (SPE) with LC/MS/MS detection and comparing it to direct injection LC/ MS/MS is presented. The performance of the method of direct injection did not significantly deviate from the SPE approach. However, the direct injection method used less sample volume (100 µl) in shorter analysis time (4 min) and allowed more sample throughput. Conversely, the uncertainty of measurement could be reduced using SPE. Key words: On-line solid phase extraction; direct injection; microcystin; LC/MS/MS

Microcystin (MC) is one of the most widespread cyanobacteria toxins found worldwide in inland and coastal water environments. They are produced by cyanobacteria (blue-green algae) that are found naturally in blooms of freshwater, lakes, streams, ponds, and other surface waters at favourable eutrophic, warm and low turbulent conditions. There are many types of MC; microcystin-LR (MC-LR) is one of the more toxic and well-studied varieties. Health effects of MC-LR can be acute or chronic and have been known to cause a tumour, liver and kidney damage potentially. The most severe consequence of exposure to MC is death. The impacts of chronic or acute exposure to MC-LR in humans, especially at the lower levels are more common via drinking water. There is also a particular concern for livestock (Fitzgerald & Poppenga 1993; Kerr, McCoy & Eaves 1987;

Moore & Puschner 2012) and canine (Wood et al., 2010; DeVries, Galey, Namikoshi & Woo 1993) exposure to MC via surface drinking water from contaminated lakes, ponds and rivers. In response to continued harmful effects of MC-LR, the Ministry of Health Malaysia (MOH) added MC-LR to its Contaminants List of unregulated contaminant and uses the Drinking Water Quality Surveillance Programme (KMAM) to monitor this pollutant in public water systems. The monitoring will provide MOH with nationally representative data on the occurrences of MC-LR in drinking water, which can support future regulatory determinations and other actions to protect public health. Under the KMAM programme, the sampling activities are carried out at water

Department of Chemistry Malaysia, Petaling Jaya, 46661 Selangor, Malaysia * Corresponding author (e-mail: malar@kimia.gov.my)


ASEAN Journal on Science and Technology for Development, 34(2), 2017

distribution system and three basic stations: water treatment intake; treatment plant outlet, and service reservoir outlet. The samples collected from these locations are monitored for MC-LR levels on a regular basis. The availability of rapid and low-cost assay is therefore essential to accommodate many routine MC analyses in water which uses no laborious technique.

analysis, therefore demanding a sample preparation step that is often time consuming, tedious, and frequently overlooked. For a sensitivity analysis, an extraction and purification step are usually necessary. However, such analysis typically depends on the complexity of a sample. Here, the study compared the method performances of on-line solid phase extraction (SPE) and direct injection in determining MC-LR in drinking water. Online SPE injection method has the advantage of reducing sample preparation steps and enabling effective pre-concentration and clean-up of samples. Alternatively, direct injection method allowed high sample throughput and shorter analysis time.

Due to the increase of water sample testing demand, a high throughput analysis applying either on-line SPE or direct injection is essential to analyse a large number of samples quickly without using labourious manual SPE technique which may contribute to high variability in the analysis results.

METHODOLOGY

In Malaysia, the maximum acceptable limit for MC-LR is set at 1 ng/ml by the National Standard Drinking water Quality which is also same with the World Health Organization recommended level of 1 ng/ml of MC-LR (free and cell bound) in drinking water for humans. Hence, an analytical method set-up which is robust and powerful for analysing drinking water contaminated with MC-LR at low levels is essential and needs to be in place. LC/MS/ MS analysis with electrospray ionization (ESI) was the method of choice for this study. The LC technique with MS/MS detector was preferred for the analysis of polar and thermally labile compounds mainly due to its selectivity and sensitivity, enabling efficient and reliable detection, and quantitation of MC-LR in drinking water.

Sample Preparation Internal standard (ISTD) solution, solution was added into water sample at 0.1 ng/ml concentration level. Then, the sample was filtered using 0.2 Âľm nylon membrane filter, before extraction by on-line SPE and followed by UPLC-MS/MS analysis. The on-line SPE procedure consisted of three steps: loading; washing; and eluting the sample analyte through the SPE cartridge with the gradient flow of conditioning and rinsing. The extracts were then analysed by LC/MS/MS. The direct injection method only involved injecting of filtered water samples into LC/MS/MS for analysis with nil preparation. Data was acquired using electrospray ionization and multiple reaction monitoring (MRM) using one precursor ion/ two product ion transitions per compound (Table 1).

Trace level analysis often adds to the challenge of direct determination of the compound of interest by chromatographic 126


Malarvili et al.: Quantitative Analysis of Microcystin-LR in Drinking Water

Table 1. Instrument condition and MS/MS setting of on-line SPE method versus direct injection. Description/ Parameters

On-line SPE

Direct injection

LC column

Waters ACQUITY UPLC BEH C18 Column, 130Å, 1.7 µm, 2.1 mm × 100 mm

Waters ACQUITY UPLC BEH C18 Column, 130Å, 1.7 µm, 2.1 mm × 50 mm

SPE column

Waters Oasis HLB Direct Connect HP column, 20 um, 2.1 mm × 30 mm

LC mobile phase

Deionised water and acetonitrile with 0.5% formic acid each.

Run time

15 min

4 min

Injection volume

1500 µl

100 µl

MS condition

Electrospray ionization (ESI) at positive mode (ESI +ve)

Capillary voltage: 0.5 kV Source temperature: 150°C Desolvation temperature: 350°C Desolvation gas flow: 650 L/hr Collision gas flow: 0.15 ml/min MRM setting (m/z: mass-tocharge; CV: cone voltage; CE: collision energy)

MC-LR:

m/z (995.7 > 135.05), CV: 70V, CE: 70 eV m/z (995.7 > 213.1), CV: 70V, CE: 60 eV

NOD (as ISTD): m/z (825.6 > 135.1), CV: 65V, CE: 60 eV

Method Validation

and accuracy of the methods were evaluated with spiked samples of low concentrations.

A sequence of water samples, blanks and controls samples were analysed using the described method. The obtained data were evaluated with a calibration for MC-LR. MCLR standards were prepared in deionised water over a range of 0.05 ng/ml to 10 ng/ml for online SPE and 0.1 ng/ml to 10 ng/ml for direct injection LC/MS/MS. Serial dilutions were obtained starting from 100 ng/ml concentration. The NOD ISTD was added to the standards and water samples at 0.1 ng/ml concentration.

RESULTS AND DISCUSSION On-line SPE Method The separation of the MC-LR was easier and distinct when using the on-line SPE method. Figure 1 presents a total ion chromatogram (TIC) with a chromatographic separation retention time ratio (RTMC-LR / RTNOD) of 1.04. Selective detection was performed in MRM mode using two characteristic transitions for the compound. The ratio of both transitions (about 0.4) was used to confirm the presence of MC-LR in water. The calibration curve working

For both methods, the LOD, signal-to-noise ratio (3 × SD, n = 10, signal-to-noise >3:1) and LOQ, (10 × LOD) were determined. Precision 127


100

MC20150605-38 Sm (Mn, 10x1)

100

0

7.00

7.30 75

7.33 97

7.50

7.50

8.00

Nodularin

8.00

Nodularin

8.50

8.56 4417

8.50

8.59 5048

9.50

Microcystin-LR

10.00

10.50

11.00

9.00

8.94 514

9.50

Microcystin-LR

10.00

10.50

11.00

Tap water sample spiked with 0.02ng/mL Microcystin-LR, 0.05 ng/ml Nodularin

9.00

8.92 1717

Tap water sample spiked with 0.05ng/mL Microcystin-LR, 0.05 ng/ml Nodularin

SPE Online Analysis

11.50

Time

11.50 MRM of 7 Channels ES+ TIC 6.09e4 Area

05-Jun-201519:16:35

MRM of 7 Channels ES+ TIC 7.31e4 Area

Figure 1. Total ion chromatogram for MC-LR spiked in tap water at concentration levels of 0.05 ng/ml and 0.02 ng/ml, respectively.

6.50

6.50 MC20150605-26 Sm (Mn, 10x1)

0

7.00

MC-LR 0.02ppb NOD 0.05ppb TW 4

%

%

128


Malarvili et al.: Quantitative Analysis of Microcystin-LR in Drinking Water

range of 0.05 ng/ml to 10.0 ng/ml is as presented in Figure 2. The calibration curve demonstrated a good linearity with correlation coefficient, r2 ≥ 0.99 and % deviation (% residual) within the acceptable range of ± 20% from the actual value. The LOD and LOQ obtained were 0.005 and 0.05 ng/ml. Good results were obtained for MC-LR fortified in tap water samples at 0.5 ng/ ml, 1 ng/ml and 1.5 ng/ml, with recoveries 97%,

102% and 102%, respectively (Table 2). The precision (<5%RSD) was rather satisfactory with results 3.3%, 3.9% and 2.5% for MC-LR fortified in tap water samples at 0.05 ng/ml, 0.1 ng/ml and 1.0 ng/mL, respectively (Table 2). The expanded combined relative uncertainty determined from the validation process was 10%.

Residual

Response

Compund name: Microcystin-LR Correlation coefficient: r = 0.998274, r^2 = 0.996552 Calibration curve: 0.613313 * x + -0.0200707 Response type: Internal Std (Ref 2), Area * (IS conc. / IS area) Curve type: Linear, Origin: Exclude, Weighting: 1/x, Axis trans: None

ng/ml

ng/ml

Figure 2. Calibration curve for MC-LR from 0.05 ng/ml to 10 ng/ml. Table 2. Comparison of results between on-line SPE method and direct injection. Description/ Parameters

Direct injection

Online SPE

Separation (RTMC-LR / RTNOD)

2.26/1.61 = 1.40

8.92/8.59 = 1.04

Linearity (internal standard calibration)

0.1 – 10 ng/ml (r2 ≥ 0.99)

0.05 – 10 ng/ml (r2 ≥ 0.99)

LOD = 3 × SD (In tap water)

0.0192 ng/ml

0.0050 ng/ml

LOQ = 10 × LOD (In tap water)

0.0959 ng/ml

0.0501 ng/ml

Precision (% RSD)

0.5 ng/ml:5% (n = 10)

0.05 ng/ml: 3.3% (n = 10)

(In tap water)

0.1 ng/ml: 4% (n = 10)

0.1 ng/ml: 3.9% (n = 10)

1 ng/ml: 17% (n = 30)

1 ng/ml: 2.5% (n = 20)

0.1 ng/ml: 119% (n = 20) 1 ng/ml: 106% (n = 10)

0.5 ng/ml: 97% (n = 10) 1 ng/ml: 102% (n = 10)

Relative recovery (%) (In tap water)

1.5 ng/ml: 102% (n = 10) Expanded combined relative uncertainty (Ucr)

19%

10%

129


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Direct Injection Method

and elution. The recovery results obtained for both methods were considered acceptable as they fall within the range of 70% to 120% [6].

The analysis time of direct injection method was only 4 min with a chromatographic separation retention time ratio of 1.40 (Figure 3). This allows high throughput sample analysis. Calibration curve for the range, 0.1 to 10.0 ng/ml displayed a good linearity with correlation coefficient, r2 ≥ 0.99 and ± 20% deviation (Figure 4). The LOD and LOQ determined were 0.019 ng/ml and 0.096 ng/ml, respectively. The recovery results of MC-LR fortified in tap water samples (Table 2) at 0.1 ng/ml and 1 ng/ml were 119% and 106%. Precision results were acceptable with <20%RSD determined as 5%, 4% and 17% for MC-LR fortified in tap water samples at 0.5 ng/ml, 0.1 ng/ml and 1.0 ng/ml respectively (Table 2). The expanded combined relative uncertainty determined from the validation process was 19%.

Both LC-MS/MS methods were also compared using statistical significance tests. The F-test was applied to determine the precision variability between the two methods, while the t-test was applied to determine if there was a significant difference between these methods. The calculated F-value, 0.03 and t-value, 0.22, were below the critical values of 2.42 and 2.01, respectively at 95% confidence level. Although measurement uncertainty for on-line SPE method was found to be almost two times lower than direct injection, the significance tests outcomes indicated that there were no significant differences between these methods. CONCLUSION

Comparison between Two Methods

On the whole, all validation results of both methods fall within the acceptable limits that complied with EU Commission Decision 2002/657/EC (Anon. 2002) and EURACHEM (Anon. 2014) guidelines requirements. Also, the statistical data proved that the two methods were equally precise and there was no significant difference between these methods. Both methods were rather simple, rapid, precise, accurate and sensitive and could be deployed for routine analysis. However, the advantage of direct injection over on-line SPE method was the former which used smaller sample volume (100 µl) and shorter analysis time (4 min) thus enabled high sample throughput.

The validation data showed that the direct injection method did not significantly deviate from the on-line SPE method. The LOD and LOQ obtained for both methods were well below than the NSDWQ standard requirements of 1 ng/ml. The slightly improved sensitivity for on-line SPE method could be explained by a lower LOD and LOQ than direct injection method due to injection of larger sample volume (1500 µl) compared with 100 µl for direct injection. Large sample volume injection was able using on-line SPE due to concentration enrichment of analyte in the SPE cartridge, thus enchase its sensitivity. However, the analysis time of on-line SPE method was much longer (15 min) compared with direct injection (4 min) as longer gradient flow time was required for multi-steps of conditioning, loading, washing,

Date of receipt: November 2017 Date of acceptance: December 2017

130


131

Figure 3. Total ion chromatogram for MC-LR spiked in tap water at concentration levels of 0.05, 0.1, and 1 ng/ml respectively.

Blank tap water without preservatives added Injection 100 ul

Blank tap water with preservatives added Injection 100 ul

Blank tap water with preservatives added spiked with Microcystin-LR 0.05 ng/ml, internal standard noduralin 0.1 ng/ml Injection 100 ul

Blank tap water with preservatives added spiked with Microcystin-LR 0.1 ng/ml, internal standard noduralin 0.1 ng/ml Injection 100 ul

Blank tap water with preservatives added spiked with Microcystin-LR 1 ng/ml, internal standard noduralin 0.1 ng/ml Injection 100 ul


ASEAN Journal on Science and Technology for Development, 34(2), 2017

Residual

Response

Compund name: Microcystin-LR Correlation coefficient: r = 0.998658, r^2 = 0.997319 Calibration curve: 0.405756 * x + -0.00651749 Response type: Internal Std (Ref 2), Area * (IS conc. / IS area) Curve type: Linear, Origin: Exclude, Weighting: 1/x, Axis trans: None

ng/ml

ng/ml

Figure 4. Calibration curve for Microcystin-LR from 0.1 ng/ml to 10 ng/ml.

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Anonymous 2002, Commission decision 2002/657/EC, implementing council directive 96/23/EC concerning the performance of analytical methods and the interpretation of results.

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Moore, CE & Puschner, B 2012, ‘Cyanobacteria’, in Small animal toxicology, 3rd edn, Chap 44, Saunders, Philadelphia, PA, USA.

DeVries, SE, Galey, FD, Namikoshi, M & Woo, JC 1993, ‘Clinical and pathologic findings of blue-green algae (Microcystis aeruginosa) intoxication in a dog’, Journal of Veterinary Diagnostic Investigation, vol. 5, pp. 403–408.

Wood, SA, Heath, MW, Holland, PT, Munday, R, McGregor, GB & Ryan, KG 2010, ‘Identification of a benthic microcystinproducing filamentous cyanobacterium (Oscillatoriales) associated with a dog poisoning in New Zealand’, Toxicon, vol. 55, pp. 897–903. [PubMed]

Fitzgerald, SD & Poppenga, RH 1993, ‘Toxicosis due to microcystin hepatotoxins

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Asean Journal on Science & Technology for Development Contents

JSTd

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Cover ASEAN AJSTD 34,2 2017.pdf

Vol. 34 No. 2, 2017 ISSN 0217-5460

A Journal of the ASEAN Committee on Science & Technology

ASEAN J. Sc. Technol. Dev. Vol. 34, No. 2, 2017

Influence of TESPT on Tensile and Tear Strengths of Vulcanized Silica-filled Natural Rubber A.K. Norizah and S. Azemi

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Assessment of Natural Radioactivity Level and Radiological Index in the Vicinity of Lynas Rare-earth Processing Plants W.M. Zal Uâ&#x20AC;&#x2122;Yun, M.W. Yii, K. Mohd Ashhar, M.K. Khairuddin, I. Abdul Kadir and Y. Mohd Abd Wahab

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Thermal Efficient Design of Distributed Memory Generator for Dual-port RAM Using Unidirectional High-performance IO Standard B. Das and M.F.L. Abdullah

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Adsorption and Diffusion Characteristics of 2-Naphthol from Aqueous Media by Chitosan-ENR Biocomposites R. Gunasunderi and M.R.H. Mas Haris

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Preparation and Characterisation of Crosslinked Natural Rubber (SMR CV 60) and Epoxidised Natural Rubber (ENR-50) Blends M. Sasitaran, S. Manroshan, C.S. Lim, B.N. Krishna Veni, S.K. Ong and R. Gunasunderi

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Diet and Exercise Decreasing Cholesterol Level among Obese Sri Lankan Patients Admitted to a Government Hospital â&#x20AC;&#x2022; A Cohort Study S. Sandasorroopan, K. Judenimal and R. (111) P. Dioso

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Quantitative Analysis of Microcystin-LR in Drinking Water Comparing On-Line Solid Phase Extraction and Direct Injection LC/MS/MS R. Malarvili, Y.Y. Low and A. Zaiton

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ASEAN Journal on Science & Technology for Development

AJSTD 34(2) 2017  
AJSTD 34(2) 2017