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 Bra bender slit capillary die. The melt shear stress and viscosity increased with filler content. The filler was treated with a silane-based coupling agent. The silane used was Prosil 2020, a proprietary silane coupling agent containing the peroxide bis(t-butyl peroxy)di-isopropyl benzene. The peroxide induces β- scission of the polypropylene molecular chains reducing the shear stress and viscosity. Hence the filler and the coupling agent (peroxide concentration) have opposing effect on the rheology of the composite's melt. For high filler content melt, the peroxide effect is more prominent, lowering the overall stress and vis cosity. At higher shear rate, the effect of filler concentration is more dominant. Mixing torque and melt flow index studies support the rheology measurements by the slit die technique.