10 - The Effect of Titanate Coupling Agent on Water Absorption and Mechanical Properties of Rice Husk Filled Poly(vinyl Chloride) Composites

Abstract

Unplasticized polyvinyl chloride (PVC-U) composites are now popular materials in the building sector. Natural fillers such as rice husk (RH) have been used to reduce cost and modify certain properties. A coupling agent is a class of additives which are used to improve the adhesion between fillers and polymer matrix. This work investigated the effects of titanate coupling agent on water absorption and mechanical properties of RH filled impact modified PVC-U composites. The composites were prepared by blending PVC, additives and RH fiber at various ratios in a laboratory blender and then sheeted on a two-roll mill. Water absorption test was carried out by immersing the samples into water for 65 days at ambient temperature. Mechanical properties of the composites were investigated by using impact and flexural test. The titanate coupling agent was found to be effective in increasing the water absorption resistance. The water absorption of treated PVC/RH20 and PVC/RH30 was reduced by 18% and 26% respectively, compared to the untreated PVC/RH20 and PVC/RH30. It suggests that the titanate coupling agent had improved the interfacial adhesion between the RH and PVC matrix in the composites, hence reducing the water uptake by the composites. The incorporation of titanate coupling agent increased the impact strength and flexural modulus of the composites but reduced the flexural strength. This may suggest that the titanate coupling agent, besides functioning as a coupling agent, can also work as a plasticizer by increasing the flexibility of the composites. The treated PVC/RH30 with flexural modulus of 3.6GPa and impact strength of 4.9kJ/m2 has the most balanced properties in terms of stiffness and toughness.