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SYNOPSISThree new types of fillers for polypropylene are investigated. The first two were derived from burnt rice husk ash (RHA), whereas the third, a wood-based filler, was processed from oil palm trunk. One important characterization of the composites involves the checking for the actual filler content and filler distribution within the matrix. An analytical technique is described here for computation of the filler content in the composites based on a simple expression derives from thermogravimetric analyses. For filler with volatiles such as the black RHA, the derived expression was pt = 1 0 6 ( r h / m ) , and for easily burnt fillers (wood-based), the expression was p f = 156(md/m,). The technique has shown good agreement and consistency between analyzed and actual filler contents and a uniform filler distribution within the polypropylene matrix.

ABSTRACT:The viability of using oil palm trunk wood flour (OPWF), a by-product of the oil palm industry, as a filler in polypropylene (PP) was studied. The OPWF was compounded into polypropylene using a Brabender thermoplastics mixer and a twin screw compounder. Torque of PP/OPWF composite was compared to that of neat polypropylene. The result showed that the mixing torque of polypropylene increases by adding OPWF filler into it. Test specimens of the PP/OPWF composite at 30% filter content were prepared by injection moulding, their mechanical properties evaluated and compared to a commercial PP /talc composite. The tensil properties, flexual modulus, impact strength, and melt flow index of the PP/OPWF composite were decreased only by a small margin when compared to those of PP/talc. The PP/OPWF composite, on the other hand, has better heat deflection temperature value than PP/talc. The study shows that OPWF has a good potential to be used as an alternative filter for polypropylene. The OPWF used in this study was not treated with any coupling agent.

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 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 βscission 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 viscosity. 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.

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