RICE HUSK ASH AS FILLER IN POLYPROPYLENE - EFFECT OF WAX AND SILANE COUPLING AGENTS

Two new types of filler for thermoplastic materials have been investig ated. Rice husk ash (RHA) when burnt yields two types of potential fil ler namely black RHA and white RHA. Polypropylene composites of differ ent filler loadings were compounded using a twin screw extruder. A mix ing study was performed using a Brabender thermoplastics mixer. The mi xing torques increase with filler contents. Thermogravimetric analysis showed a good agreement between analysed and actual filler content an d a uniform filler distribution in the composites. Flexural modulus sh owed an increase whereas tensile strength, elongation at break and imp act strength decreased with increasing filler content. An attempt to i mprove these properties with Epolene wax as a coupling agent was unsuc cessful due to suspected compatibility problems. Silane coupling agent , Prosil 2020 reduced mixing torque, improved the tensile strength of the composites and maintained the trend of increasing flexural modulus with filler loadings. The impact strength and elongation at break val ues, however, dropped rather low, seemingly an inevitable trade-off to achieve higher stiffness.