A comparative study on processing, mechanical properties, thermo-oxidative aging, water absorption, and morphology of, rice husk powder and silica fillers in polystyrene/styrene butadiene rubber blends

Rice husk powder (RHP) and silica-filled polystyrene (PS)/styrene butadiene rubber (SBR) composites were prepared by using the laboratory size internal mixer (Brabender Plasti-corder). The torque development, morphology, and mechanical properties such as tensile strength, elongation at break, Young modulus, and impact strength were studied. Water absorption and the effect of thermo-oxidative aging on tensile properties of composites were also examined. Filler loading and filler type influence the processibility of the composites in which RHP offers better processing advantage over silica. Tensile strength reduces with increasing filler loading for both RHP and silica composites. However, at 15 wt% the fillers act as reinforced materials to the composites. Young modulus also increases with increasing filler loading, whereas elongation at break shows no significant changes. Aging test results show that the tensile strength and elongation at break decrease and Young modulus increases with aging for RHP composites. However, for silica composites, there were no significant changes in Young modulus and elongation at break except reduction of tensile strength. The water uptake in RHP composites is higher than silica composites. Scanning electron microscopy on fracture surface shows poor filler matrix adhesion with the increasing of filler loading in the composite. This explains the reduction of tensile strength before and after aging with increasing filler loading.