RICE HUSK ASH (RHA)-BASED SILICA AS FILLER IN POLYPROPYLENE COMPOSITE- EFFECT OF PEROXIDE-CONTAINING SILANE ON THE RHEOLOGICAL BEHAVIOR

The effect of incorporating silica filler derived from rice husk ash ( RHA) on the rheological properties of polypropylene was studied using a Brabender slit capillary die. The melt shear stress and viscosity in creased with filler content. The filler was treated with a silane-base d coupling agent. The silane used was Prosil 2020, a proprietary silan e coupling agent containing the peroxide bis(t-butyl peroxy)di-isoprop yl benzene. The peroxide induces beta-scission of the polypropylene mo lecular chains reducing the shear stress and viscosity. Hence the fill er and the coupling agent (peroxide concentration) have opposing effec t on the rheology of the composite's melt. For high filler content mel t, the peroxide effect is more prominent, lowering the overall stress and viscosity. At higher shear rate, the effect of filler concentratio n is more dominant. Mixing torque and melt flow index studies support the rheology measurements by the slit die technique.