Effect of filler size and loading on thermo-mechanical degradation of polypropylene-ethylene/wollastonite composite

This study is to understand the side effect of wollastonite fillers in polymer compounding that caused different levels of thermo-mechanical degradation (TMD) during extrusion. Wollastonite has a needle-like structure with different ratio of L/D; it compounded with the polypropylene-ethylene copolymer (PPcoE) using a twin-screw extruder. The effect on the TMD of PPcoE was determined by analysing the by-products within the extrudates via FTIR. The rheology of PPcoE composite was measured using a capillary rheometer, and the thermal stability of composite was studied using TGA. In this study, TMD is classified as two levels: chain scission and oxidisation. The wollastonite filler were found to accelerate the TMD mechanism and generated oxidised products during extrusion. The reduction of filler size effectively minimised the chain cleavage of PPcoE matrix, also come with improvement in thermal stability. However, increasing the filler loading had a dominant effect of inducing more chain cleavage on the polymer matrix.