School of Materials Engineering, Universiti Malaysia Perlis (UniMAP), Kompleks Taman Muhibah, Jejawi 2, Arau, Perlis, Malaysia.

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1 Recycled High Density Polyethylene/Ethylene Vinyl Acetate (RHDPE/EVA)/Taro Powder (Colocasia esculenta) Composites: The Effect of Caprolactam-Maleic Anhydride on Tensile Properties and Morphology A. R. H. Fatimah *,1,a, A. G. Supri 2,b and Z. Fairuz 1,c 1 School of Materials Engineering, Universiti Malaysia Perlis (UniMAP), Kompleks Taman Muhibah, Jejawi 2, Arau, Perlis, Malaysia. 2 Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP), Main Campus, Pauh Putra, Arau, Perlis, Malaysia. a,* fatimahrajak@gmail.com, b supri@unimap.edu.my, c firuz@unimap.edu.my Abstract Natural fillers fulfil most requirements needed to replace synthetic fillers in thermoplastic composites. However, some disadvantages appear when natural fillers are used for composites. The poor compatibility between the hydrophilic fillers with the hydrophobic polymer matrix leads to a weak interface and hence, poor mechanical properties. In this research, the caprolactam-maleic anhydride (CL-MAH) was used as a compatibilizer. The tensile strength of RHDPE/EVA/Taro powder composites decreased with increasing filler loading, while adding caprolactam-maleic anhydride in the composite significantly improved the tensile properties. The SEM morphology of tensile fracture surfaces of RHDPE/EVA/Taro powder composites shows better interfacial interaction between taro powder and RHDPE/EVA phases with the incidence of CL-MAH as a compatibilizer. Copyright 2014 Penerbit - All rights reserved. Keywords: Recycled High Density Polyethylene, Ethylene Vinyl Acetate, Taro Fillers, Caprolactam-Maleic Anhydride 1.0 INTRODUCTION Polymer composites have been widely used for several years to meet the demand for materials that provide higher standards of performance and reliability [1,2]. Composites are combinations of at least two materials, which are matrix and filler as reinforcement. The matrix material surrounds the filler by maintaining their relative positions [3,4]. The use of natural fillers as reinforcement of composites receives a lot of attentions from many plasticbased industries. These natural fillers offer such advantages as low weight, widely available, enhanced biodegradability, low cost, high filling levels possible, and high specific mechanical properties of composites [5,6,7]. However, poor interfacial properties in the form of poor adhesion between the hydrophilic lignocellulosic fillers and hydrophobic matrices reduce the potential of natural fillers as reinforcing agents and weaken the mechanical properties of the final composites. The interface, which is an important aspect to determine the physical and mechanical properties of composites, can be improved by the use of compatibilizing agents. Compatibilizers have the ability to react with organic fillers and 1

2 matrices, forming bridges across the interface [8,9]. The aims of this study are to investigate the effects of different taro filler loadings and the use of caprolactam-maleic anhydride as a compatibilizer on the tensile properties and morphology of recycled high density polyethylene/ethylene vinyl acetate/taro filler. This research needs to be improved by refining the reaction of two different compatibilizers, caprolactam and maleic anhydride, hence, improved the blending of RHDPE with EVA. Besides that, the addition of filler loading also needs to be enhanced because this will lead to superior tensile properties, which makes taro powder as useful organic filler for commercial product. 2.0 METHODOLOGY 2.1 Materials. RHDPE with melt flow index of 0.7 g/10 min (190 C) and density of kg/m 3 was used. EVA, which contains 18.1 wt% VA, melt index of 2.5 g/10 min (80 C, 2.16 kg) and density of 0.93 g/cm 3 was supplied from A.R. Alatan Sdn. Bhd., Kedah Darul Aman, Malaysia. Taro filler was obtained from a local village in Selangor. The ingredients of taro are shown in Table 1. Maleic anhydride was supplied by Zarm Scientific & Supplier Sdn. Bhd., Penang, Malaysia. Caprolactam and dibenzoyl peroxide (BPO) were obtained from A.R. Alatan Sdn. Bhd., Kedah Darul Aman, Malaysia. Table 1: Ingredients of taro powder (TP) as determined from the Laboratory Department of DXN Holdings Bhd., Jitra, Kedah. Content Quantity Calories (Kcal) Carbohydrate (%) 52.6 Fat (%) 1.2 Protein (%) Sample Preparation. The stems from taro plants were cut, washed, dried, and grinded to powder by using a grinder machine. Taro fillers with average sizes of 75 µm were dried in a vacuum oven at 80 C for 1 h. For composites preparation, the compounding of the blends was carried out by melt blending in a Brabender internal mixer. The RHDPE was first mixed in the internal mixer at 160 C with the speed of 50 rpm for 2 min, followed by the addition of EVA and mixed until homogenous. The compatibilizers, CL-MAH, dibenzoyl peroxide (DBP), and TP were added to the mixer for the remaining minutes. Each of the compounding step was compression molded into sheets of 2 mm thickness using a hydraulic press at 160 C for 6 min and cooled under pressure for 4 min. Table 2 shows the formulation used in this study. 2

3 Table 2: Formulations of RHDPE/EVA/TP composites and RHDPE/EVA/TP -CL-MAH composites. Composite Code RHDPE EVA TP CL-MAH DBP RHDPE/EVA/TP RHDPE/EVA/TP RHDPE/EVA/TP RHDPE/EVA/TP RHDPE/EVA/TP RHDPE/EVA/TP5-CL-MAH RHDPE/EVA/TP10-CL-MAH RHDPE/EVA/TP15-CL-MAH RHDPE/EVA/TP20-CL-MAH RHDPE/EVA/TP25 -CL-MAH Characterization and Measurements. Tensile properties of the composites were measured by using Universal Testing Machine Instron 5582 with crosshead speed of 30 mm/min. Dumbbell-shaped specimens were conditioned at ambient temperature before testing. Studies on surface morphology of the RHDPE/EVA/TP composites with and without compatibilizer were carried out using SEM. Surfaces of the samples were coated with a thin platinum layer about 12 µm thickness using the Auto Fine Coater to avoid electrostatic charged during examination. 3

4 3.0 RESULTS AND DISCUSSION 3.1 Tensile Properties Fig. 1(a) shows the effect of different filler loadings of taro fillers on the tensile strength of RHDPE/EVA composites. The results show that the tensile strength of RHDPE/EVA/Taro powder composites decreased with the increase in taro fillers content. Such decline in tensile strength is credited to the weak bonding formed between the polar hydrophilic taro fillers and non-polar hydrophobic RHDPE/EVA composites. The increase in filler content also resulted in agglomeration of dispersed filler particles and consequently reduced the tensile strength due to the lower strength of the agglomerates. Similar results were testified by Kim et al. [10], where for the addition of bio-flour loading, the tensile strength of the composites decreased due to weak interfacial adhesion between hydrophilic bio-flour and hydrophobic polypropylene. In addition, Fig. 1(a) also indicates that the tensile strength of the RHDPE/EVA/Taro powder composites increased with the presence of CL-MAH. The result suggests that the interfacial adhesion has evidently improved between the RHDPE/EVA phases and the taro powder, leading to an improvement of tensile strength of the composites [11,12]. Liu et al. [13] conducted a study on the effect of two modifiers, PE-g-MAH and maleated ethylene/propylene elastomers (EPR-g-MAH) on the matrix of HDPE and bamboo flour (BF), which resulted in increased tensile strength of the composites compared to HDPE/BF composites alone. RHDPE80/EVA20 RHDPE80/EVA20/CL-MAH RHDPE80/EVA20 RHDPE80/EVA20/CL-MAH Tensile Strength (Mpa) Filler Loadings (phr) Elongation at Break (%) Filler Loadings (phr) (a) (b) Figure 1: Tensile properties of RHDPE/EVA/Taro powder composites and RHDPE/EVA/Taro powder/cl-mah composites with different filler loadings (a) Tensile strength and (b) elongation at break Fig. 1(b) also shows the effect of different filler loadings and compatibilizer on elongation at break of RHDPE/EVA/Taro powder composites. The addition of taro powder with different filler loadings reduced the toughness of the RHDPE/EVA composites. As taro filler increased, the elongation at break decreased gradually as the filler forces the matrix to deform 4

5 Penerbit more than the overall deformation of composites due to the fact that deformation of filler is commonly less than matrix. At similar filler loading, the RHDPE/EVA/TP/CL-MAH composites had lower elongation at break than RHDPE/EVA/TP composites. This is due to good interfacial adhesion between filler and matrix, which then increased the stiffness of the composites and consequently reduced the elongation at break [10]. 3.2 Morphology Analysis Fig. 2 shows SEM micrograph of tensile fracture surface of RHDPE/EVA/TP and RHDPE/EVA/TP/CL-MAH composites at different taro powder loadings. Figs. 2(a), 2(b), and 2(c) show the incompatibility of the composites, as the fracture surfaces indicate weak adhesion between the matrix and taro powder due to the presence of many voids within the surface. This low adhesion had given rise to poor stress transfer across the interfaces when stress was applied. The number of voids positioned in the fracture surfaces was due to poor dispersion of taro powder in RHDPE/EVA blends. The amount of voids increased with increasing content of filler due to the absence of a compatibilizer. The addition of CL-MAH as a compatibilizer improved the interfacial adhesion between taro powders with RHDPE/EVA phases as shown in Figs. 2(d), 2(e), and 2(f). By closely examining these three figures, it could be observed that the filler was strongly bonded to the polymer due to less microvoids and filler-matrix debonding in the interphase region. A similar observation was reported by Ayrilmis et al. [10] for the compatibilization of composites. In addition, due to the presence of a compatibilizer, the tensile fractured surfaces have rough and good interaction between the filler and the matrix. (a) (b) (d) (e) (c) (f) Figure 2: Scanning electron micrographs of tensile fracture surfaces of RHDPE/EVA/TP composites and RHDPE/EVA/TP/CL-MAH composites with different filler loadings. (a) RHDPE/EVA/TP-5, (b) RHDPE/EVA/TP-15, (c) RHDPE/EVA/TP-25, (d) 5

6 RHDPE/EVA/TP-5/CL-MAH, (e) RHDPE/EVA/TP-15/CL-MAH, (f) RHDPE/EVA/TP- 25/CL-MAH. 4.0 CONCLUSION The RHDPE/EVA/TP/CL-MAH composites have higher tensile strength but lower elongation at break compared to RHDPE/EVA/TP composites. The addition of CL-MAH as a compatibilizer improved the compatibility and stress transfers of the composites and simultaneously improved the interfacial adhesion between taro powder and RHDPE/EVA phases. REFERENCES [1] F.P. La Mantia, M. Morreale, Green composites: A brief review, Composites: Part A 42 (2011) [2] F. Klaus, F. Stoyko, Z. Zhong, Polymer Composite, from Nano- to Macro-Scale, Springer, Berlin, [3] R.N. Rothon, Particle-filled Polymer Composites, second ed., Rapra Technology, Shrewsbury, UK, [4] A.R.H. Fatimah, A.A.H. Ikmal, A.G. Supri, Effect of PEgMAH on tensile properties and swelling behavior of recycled high density polyethylene/ethylene vinyl acetate/waste tyre dust (r-hdpe/eva/wtd) composites, Advance Mechanics and Materials 554 (2014) [5] D.N. Saheb, J.P. Jog, Natural fiber polymer composites: A review, Advances in Polymer Technology Vol. 18 No. 4 (1999) [6] N. Stevulova, E. Terpakova, J. Cigasova, J. Junak, L. Kidalova, Chemically treated hemp shives as a suitable organic filler for lightweight composites preparing, Procedia Engineering 42 (2012) [7] R. M. Rowell, Challenges in biomass-thermoplastic composites, J Polym Environ 15 (2007) [8] N. Bakar, C.Y. Chee, L.C. Abdullah, C.T. Ratnam, N. Azowa, Effect of methyl methacrylate grafted kenaf on mechanical properties of polyvinyl chloride/ethylene vinyl acetate composites, Composites: Part A 63 (2014) [9] V. Mittal, Functional Polymer Blend: Synthesis, Properties, and Performance, Taylor & Francis Group, FL, [10] H.S. Kim, B.H. Lee, S.W. Choi, S. Kim, H.J. Kim, The effect of types of maleic anhydride-grafted polypropylene (MAPP) on the interfacial adhesion properties of bio- flour-filled polypropylene composites, Composites: Part A 38 (2007) [11] K. Ahmed, N.Z. Raza, F. Habib, M. Aijaz, M.H. Afridi, An investigation on the influence of filler loading and compatibilizer on the properties of polypropylene/marble 6

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