(UiTM), Shah Alam, Selangor,Malaysia. Selangor,Malaysia. Keywords: Aromatic oil, Epoxidized Oil, Natural Rubber, Tensile Strength, Tear Strength

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1 Advanced Materials Research Online: ISSN: , Vol. 812, pp doi: / Trans Tech Publications, Switzerland Effect of Epoxidized Oil on Tensile and Tear Strength of NR Vulcanizate and its Comparison with Aromatic Oil NR Vulcanizates RAHMAH Mohamed 1,a,NORAZIRA Wan Zain 2, AHMAD Faiza 3, Mohd Nurazzi Norizan 4, 1 GREEN Polymer Research Group, Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), Shah Alam, Selangor,Malaysia 2,3,4 Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), Shah Alam, Selangor,Malaysia a greenkayangan@gmail.com Keywords: Aromatic oil, Epoxidized Oil, Natural Rubber, Tensile Strength, Tear Strength Abstract. Epoxidized oil (EO) is a sustainable oil that can be obtained form edible or non-edible naturals oil. The incorporation of epoxidized oil can increase the green component in rubber compound. It can contributes to worldwide technology specially in green tyre manufacturing. Epoxidized oil has the potential to replace aromatic oil (AO) to rubber and polymer industry. The effect of incorporation of EO and AO into natural rubber vulcanizates (NR) was studied via tensile and tear strength tests according to ISO and ISO 6133, respectively. Tensile strength of AO value showed greather value compared to EO. Gradual increases of elongation were observed form both AO and EO. Both moduli at 100% and 300% elongation, showed reductions as oil loading were increased. The tear strength results showed that tearing energy insignificantly increased with oil loading. EO compound was found to possess higher tearing energy compared to AO compound for most composition except for 15 pphr EO. Introduction Oil is one of the substances that are typically used processing aid especially for high filler loadings in formulating rubber compound. [1]. There are three types of petroleum oils used as processing aids and extenders in rubber compound such as paraffinic, naphthenic or aromatic oil [2]. However the aromatic oil has disadvantage in that, it is hazardous to the environment. High aromatic (HA) oils are suspected as toxic and has been labeled as carcinogenic. In this research work, aromatic oil was replaced by epoxidized oil (EO) by evaluated EO as the rubber processing oil. It is known epoxidized fatty acid derivatives from vegetables sources can be used in various domains, for example as stabilisers and plasticiser in polymer, as additives in lubricants, as components in plastic and in urethane foams [3]. Vegetable sources such as soy bean and jatropha oil have high content of unsaturated fatty acid. These acids are used in the reaction to produce high epoxy functionality materials [4]. In addition, plant seeds are sustainable and their oils are less harmful to the human health, and are suggested as potential rubber process oil in the rubber compounding. Tread hardness or softness at low temperatures is the major factor in determining ice traction properties. The lower glass transition temperature of NR (natural rubber) /SBR (styrene butadiene rubber) is beneficial. For wet skid resistance a tread needs to be hysteretic at the ploughing frequency of road asperities, so oil-extension is used to improve the wet traction of NR. The oils used were optimized for type and amount for an even better balance of tyre characteristics based on oil extended natural rubber (OENR) formulation. Rolling resistance was significantly lowered as the OENR content increases and this can contribute to fuel saving [5, 6]. Blends of natural rubber/virgin ethylene-propylene-diene-monomer (NR/EPDM) and natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) with carbon black had been studied in other research. The tested rubber compounds indicated that curing characteristics with All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/05/16,12:51:57)

2 Advanced Materials Research Vol different blend system affected the strength performance. Mineral oils like aromatic and naphthenic oils are the most common processing oils in the rubber industry. In their work, rice bran oil had been used as for processing oil as a much cheaper substitute in India [7]. Materials In this research, the main raw materials used were natural rubber, NR (SMR 10), styrene butadiene rubber SBR( NIPOL 1502), epoxidized oil, (HAF N330), aromatic oil (Tudalen 65), zinc oxide (activator), stearic acid, antioxidant (Santoflex 13), and cyclohexylbenzothiazole -2- sulphenamide CBS( accelerator). Table 1 Compound Formulation used with Different Loadings of AO And EO in Part Per Hundred Rubber (pphr) Mix number NR (SMR 10) SBR (NIPOL 1502) Zinc Oxide Stearic Acid Santoflex HAF (N330) Epoxidized oil/ Aromatic oil Sulphur CBS Methodology All the ingredients (except sulphur and accelerator) were homogenously mixed using Banbury mixer (BR1600) to produce the masterbatch compound. Six compound mix were performed and mixing were done prior to formulation as tabulated in Table 1. The compounding was performed at 110 C and 70 rpm. Mixing of sulphur was done via two roll-mill. After mastication and mixing process, the process continued with the preparation of test pieces by using compression mold in an hydraulic press at 150 C with cure time t₉₀ [2]. Optimum cure = ( t max - t min ) t min (1) t max : Maximum temperature t min : Minimum temperature Mechanical properties. The effect of incorporation of EO and AO into natural rubber vulcanizates (NR) tensile strength was analyzed using a tensile testing machine with crosshead speed of 500 mm/minutes for tensile test and speed of 100 ± 10 mm/minutes for tear, were tested according to ISO and ISO 6133 respectively. Results and Discussion Tensile Strength, Elongation and Modulus Elasticity. The tensile strength of rubber quantifies how much stress the material will endure before failing. Fig. 1 showed that tensile strength had been reduced by increasing oil composition.

3 206 Progress in Polymer and Rubber Technology Fig. 1 Tensile strength (MPa) against oil loadings The reduction of the tensile strength was caused by the interaction and bonding between rubber chain and fillers. The strength was reduced as EO had interdiffused into the rubber system and interfered with the bonding between them. Greater tensile strength reduction was observed with EO compared to AO addition. At 15% composition of oil, AO tensile strength was reduced to only 10% as compared to EO with 40% reduction. However higher composition of 30% EO, tensile strength reduction was lower compared to rubber compound with AO loadings. In this study, the rubber strength was influenced by the oil loading and also characteristic of both aromatic and epoxidized oil. Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds with two or more fused aromatic rings containing only carbon and hydrogen atoms. They have relatively low solubility in water, but are highly lipophilic [8, 9]. Strong interaction of aromatic oil with rubber were achieved as aromatic oil has high C-H content and its physical and chemical properties of PAHs are determined by their conjugated p- electron systems. Epoxidized oil has long conjugated aliphatic chain with epoxy groups, hence glyceride chain which are the main components of epoxidized oil can diffused easily with greater mobility into rubber chain unit. Based on Fig. 2, maximum elongation versus oil loading showed a significant increased by an increase of about 20% elongation as oil loadings increased. At higher oil loading of 30 pphr, AO loadings elongation was reduced to about 35%. According to free Volume theory, because of plasticizer small molecular size compared to polymers, polymer mobility is assisted. This is attributed to increased free volume until the temperature at which the polymer-plasticizer mixture freezes [10]. pphr Fig. 2 Effect of AO and EO loadings on elongation of rubber Fig. 3 Modulus 100% (Mpa) versus Oil loading

4 Advanced Materials Research Vol Modulus of Elasticity at 100% Strain. Fig. 3 revealed the different values of moduli at 100 % strain (M 100 ) of both AO and EO of tensile testing. Generally,modulus is related to stiffness or capability to withstand a force without being deformed. M 100 for both oil showed a reduction as oil loading increases. The modulus M 100 for unfilled plasticiser are 3.0Pa and incorporation of both AO and EO had plasticised the rubber, reducing its modulus as the oil had enhanced the mobility of the rubber chain. Modulus of Elasticity at 300% Strain. Parameter at modulus 300% is measurement of stress at 300% elongation. Higher elongation cause chain stiffening which cause higher resilience due to strain crystallisation upon higher elongation. According to Fig. 4 showed the modulus at 300% (M 300 ) was reduced with increased of AO and EO loadings. Upon longer elongation, modulus of elasticity taken at M300 are much higher and increasing elongation had stiffening effect to chain, making rubber compound resilient. Reduction of modulus was greater with EO at 30 pphr loadings. 300% strain showed EO loading exhibited exponential decrease against modulus while AO has insignificant trend of decreased. The EO oil could have imparted a plasticizing effect to the rubber polymer increasing the freedom of movements of the polymer chains due to breakdown of the polymer-polymer interactions. Thereafter, the dual interaction of EO can take place between the elastomer chains and carbon black particles facilitating dispersion of carbon black [11]. Tear Behavior. It has been widely reported that the rate of crack growth in a rubber is determined by a characteristic energy per unit area of the fracture surface created, often known as the tearing energy or the strain energy release rate [5]. Based on Fig. 5, higher tearing energy of rubber with EO loading were exhibited compared to rubber with AO loading with optimum tear energy at 10%. This was due to the characteristic of EO which under certain condition becomes stiffer and eventually turned into rigid materials that influence the tearing energy [9]. Fig. 4 Modulus 300% (Mpa) versus Oil Fig. 5 Tearing energy versus oil loading of AO and EO

5 208 Progress in Polymer and Rubber Technology Fig. 6 Example of the different types of crack propagation of tear behavior Overall tear energy was found to be influenced by the viscoelastic properties, residual stress and coupling parameter, resulting in chain slippage due to variation in the degree of miscibility between the component phases [6]. Conclusion As conclusion, the recent change in world scenario towards green product is to shift the use of unfriendly processing oil, aromatic oil (PAH) to sustainable oil that is less harmful. Due to better performance obtained from various testing performed, it revealed that EO and AO have their own strength properties. The values of tensile strength, elongation at break, modulus at 100% strain, modulus at 300% strain and tearing energy had resulted in more or less comparable tear strength among both types of oil. However, EO rubber compound exhibited better performance for elongation and tearing energy. In some instances, EO and AO rubber compounds showed similar tearing energy at 15% loadings. Acknowledgement The authors are greatful to Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM) Shah Alam for the facilities, equipments, also for Science Excellent Fund (600-RMI/DANA 5/3/RIF(64/2012)) received for financial support and those who have involved in making this project successful. References [1] S. Dasgupta, S.L. Agrawal, S. Bandyopadhyay, S. Chakraborty, R. Mukhopadhyay, R.K. Malkani and S.C. Ameta, Characterization of eco-friendly processing aids for rubber compound. Polymer Testing, Vol 26(4) (2007), p [2] A, Samsuri, An Introduction to Polymer Science and Rubber Technology, Pusat Penerbitan Universiti, Universiti Teknologi MARA [3] C. Decker, T. Nguyen Thi Viet, D. Decker and E. Weber-Koehl, UV-radiation curing of acrylate/epoxide systems. Polymer, Vol 42(13) (2001), p [4] N.T. Pim-pahn Meyer, M. Salamah, S. Sasitorn, J. Wannapit and T. Chakrit Epoxidation of Soybean Oil and Jatropha Oil, Int.J. Sc. Tech, Vol (13) (2008), Special edition: p. 5. [5] K. Sakulkaew, A.G. Thomas, J.J.C. Busfield, The effect of the rate of strain on tearing in rubber. Polymer Testing, Vol 30(2) (2011), p

6 Advanced Materials Research Vol [6] K. Agarwal, D.K. Setua, and K. Sekhar, Scanning electron microscopy study on the influence of temperature on tear strength and failure mechanism of natural rubber vulcanizates, Polymer Testing, Vol 24(6) (2005), p [7] A.P. Kuriakose, G. Rajendran, Rice bran oil as a novel compounding ingredient in sulphur vulcanization of natural rubber, European Polymer Journal, Vol 31(6) (1995), p [8] Copenhagen, World Health Organization Regional Office for Europe, Copenhagen, Air Quality Guidelines for Europe, (1987). [9] Agency for Toxic Substances and Disease Registry (ATSDR) Atlanta, G.U.S.D.O.H.A.H.S., Public Health Service, Toxicological profile for Polycyclic Aromatic Hydrocarbons (PAHs), (1995). [10] A.K, Doolittle, Mechanism of Plasticization, Reinhold, New York, (1965). [11] G. Chandrasekara, M.K. Mahanama, D.G. Edirisinghe, L. Karunanayake, Study on natural oils as alternative processing aids and activators in carbon black filled natural rubber, Journal of the National Science Foundation of Sri Lanka, 37(3) (2009).

7 Progress in Polymer and Rubber Technology / Effect of Epoxidized Oil on Tensile and Tear Strength of NR Vulcanizate and its Comparison with Aromatic Oil NR Vulcanizates /