Tensile Properties, Swelling, and Water Absorption Behavior of Rice-Husk-Powder-Filled Polypropylene/ (Recycled Acrylonitrile-Butadiene Rubber) Composites H. Ismail, 1 S. Ragunathan, 1 K. Hussin 2 1 School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Penang, Malaysia 2 School of Environmental Engineering, Universiti Malaysia Perlis, Perlis, Malaysia The effect of rice husk powder (RHP) on the tensile properties, swelling, water absorption, and morphology of polypropylene (PP)/[recycled acrylonitrile-butadiene rubber (NBRr)]/RHP composites was studied. Compo- sites containing 0 to 30 parts of RHP per hundred parts of resin were prepared by using a Haake Rheomix Polydrive R 600/610 mixer at 1808C with a rotor speed of 50 rpm. Results indicated that the tensile strength and elongation at break decreased but that the tensile modulus increased with increasing amounts of RHP. Swelling of the PP/NBRr/RHP composites in oil and toluene increased with increasing RHP contents, and the composites exhibited a non-Fickian diffusion with a two stage absorption mechanism. Micrographs acquired by SEM revealed an increasing number of voids and micro-holes on the tensile-fractured surfaces of the composites with increasing amounts of RHP. J. VINYL ADDIT. TECHNOL., 17:190–197, 2011. ª 2011 Society of Plastics Engineers INTRODUCTION Thermoplastic elastomers (TPEs) are substances hav- ing the processing behavior of a thermoplastic and the properties of elastomers [1]. Among the different types of TPEs, those prepared by the physical blending of a polyolefin and an elastomer have gained attention due to the simple method of preparation [1, 2]. It was reported [2] that better tensile properties were obtained when the rubber and polyolefin have some similarity in chain structure and are compatible, e.g., EPDM and polypropylene (PP) blends. Lignocellulosic-plastic com- posites are a new group of composites in which natural fibers are introduced into a plastic material by using different plastic processing technologies. These compo- sites are cheaper and have higher strength and modulus in comparison with the composites produced with syn- thetic fibers [3]. Rice husk (RH) is among the natural fibers. It is the outer covering of paddy and accounts for 20% of its weight [4]. It is necessary to investigate the possibility of using RH, an unwanted material obtained after rice milling, in plastic materials and in making useful com- posites. It has been disposed of by open burning and has become a serious environmental problem. The use of rice husk powder (RHP) as a filler in polymers may serve as an alternative to utilize this waste material [4, 5]. It is expected that lignocellulosic composites would have several advantages over the composites produced from synthetic fibers. The advantages of using this nat- ural fiber in composites are its low density, recyclabil- ity, low production cost in molded products, and biode- gradability [5, 6]. Although a large number of published papers exists on PP/RH composites [7–14], and the use of white rice husk ash (WRHA) and black rice husk ash (BRHA) in plastics [15–29], there was no work reported on the use of recycled acrylonitrile-butadiene rubber (NBRr) in PP in the presence of RHP filler. The objective of this work was to explore the mechanical properties, swelling behavior, and water absorption capacity of PP/ NBRr/RHP composites. The effects of RHP loading on tensile properties, modulus, elongation at break, swel- ling in oil and toluene, and water absorption of the PP/NBRr/RHP composites was studied. The fracture surface of the composites was also examined to study the fiber-matrix interaction and the distribution of fiber into the matrix. EXPERIMENTAL Materials The materials used for the preparation of the PP/NBRr/ RHP composites are shown in Table 1. Correspondence to: H. Ismail; e-mail: hanafi@eng.usm.my DOI 10.1002/vnl.20261 Published online in Wiley Online Library (wileyonlinelibrary.com). Ó 2011 Society of Plastics Engineers JOURNAL OF VINYL & ADDITIVE TECHNOLOGY——2011