Effects of ethylene octene copolymer and ultrafine wollastonite on the properties and morphology of polypropylene-based composites

The mechanical and thermal properties of polypropylene (PP)/ethylene octene copolymer (EOC)/wollastonite composites were investigated as a function of their composition in comparison to PP/EOC blends and native PP. PP was melt mixed with two loadings of EOC (20 and 30% (w/w)); and for the composites, each of these were mixed with three loadings of wollastonite (10, 20 and 30 parts by weight per hundred of the PP/EOC resin) on a twin-screw extruder and then injection molded. Both PP/EOC blends provided a higher elongation at break and impact strength but a lower tensile strength and modulus, storage modulus and flexural strength and modulus when compared with those of the neat PP. The addition of ultrafine wollastonite (particle size of 1200 mesh) into the blends increased the tensile modulus, storage modulus, flexural strength and modulus and impact strength in a dose-dependent manner. Thus, the combined use of EOC and wollastonite can provide balanced mechanical properties to PP. Moreover, thermogravimetric analysis showed that although the degradation temperatures of the composites were not improved, the char formation was remarkably increased with increasing wollastonite loadings.