APPLICATION OF RICE HUSK ASH AS FILLERS IN POLYPROPYLENE - EFFECT OF TITANATE, ZIRCONATE AND SILANE COUPLING AGENTS

The effects of applying titanate (LICA 38), zirconate (NZ 44) and silanes (PROSIL 2020 and PROSIL 9234) coupling agents to rice husk ash (RHA) in polypropylene composites are described. RHA consists predominantly of silica. Polypropylene composites of 10-40 wt% filler loadings were compounded using a Brabender twin screw extruder. The melt flow index decreased with filler content but for the composite treated with the built-in peroxide generator (PROSIL 2020), the reverse was true. For most of the composites, the flexural modulus increased with filler content while tensile strength, elongation at break and Izod impact strength showed a decrease. PROSIL 2020 coupling agent improved the tensile strength of the composites most, while the impact properties were enhanced by the LICA 38 and the PROSIL 9234 coupling agents. None of the coupling agents increased the stiffness of the composites except for NZ 44 at maximum filler loading. The mechanical properties of the RHA composites were compared to polypropylene composites filled with commercial fumed silica and talc,