The reinforcing effect of chopped rice husk (CRH) into polypropylene has been studied. Composites containing different amounts of CRH with 0 to 40 parts perhundred part of polymer (php) were prepared using a co-rotating twin screwextruder and characterized by mechanical properties and also water absorption. Inorder to increase the interphase adhesion, polypropylene grafted with maleic anhy-dride was added as a coupling agent to all the composites studied. It was found thatthe tensile and flexural modulus of the composites containing 40 php of CRHincreased approximately by 33% and 100%, respectively. The results also showed thatwhile flexural strength was moderately improved by increasing of CRH into the matrix,elongation-at-break and energy-at-break decreased dramatically. Areasonable adhe-sion between the main components was also observed by examining the scanningelectron micrographs. Water absorption experiments showed that although the diffu-sion coefficient increased with CRH loading, all the composites followed case I diffu-sion.
INTRODUCTION
Lignocellulosic-plastic compositesare a new group of composites inwhich natural fibres are introducedin a plastic material by using differ-ent plastic processing technologies.These composites are cheaper andhave higher strength and modulusin comparison with the composite produced with synthetic fibres spe-cially, when differences betweenfibres densities are considered [1].The main groups of plastics thatare used in lignocellulosic-plasticcomposites are semicrystalline plastics such as polyethylene (PE)and polypropylene (PP). Only ther-moplastics that melt at tempera-tures below 200ºC are commonlyused in making the composites because of the limited thermal sta- bility of natural fibres. Currently,PE is the most attractive thermo- plastic in making the natural fibre- plastic composites which are main-
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