Properties of polypropylene copolymer-mica composites

Crystallisation behaviour, morphology, dynamic mechanical, and mechanical properties have been studied for polypropylene copolymer (PP)-mica composites at various mica concentrations. Both treated and untreated mica significantly increased the modulus and improved the tensile and bending strength of the composites. Dynamic mechanical analysis indicates that the composites possess higher stiffness over a broad temperature range. Conversely, addition of both types of mica results in a deterioration of the notched impact strength. The reinforcing effect of the treated mica to the PP appears to be better than that of the untreated mica, whereas the impact properties of PP-treated mica and PP-untreated mica composites are similar at the same composition. According to morphological and crystallisation observations for the composites, the enhanced modulus, tensile, and bending strength can be attributed to alignment and orientation of the mica in the flow direction during injection moulding. The low impact strength of both composites results from the role of mica as a stress concentrator and also to the change in the microstructure of the matrix because of the nucleating effect of both types of mica on PP. By correlating the dynamic mechanical and mechanical properties to the morphology for both composites, the mica treated with a silane coupling agent enhances interfacial interaction with PP to a certain extent, compared with untreated mica.