Mechanical and Thermal Properties of Microfibrillar Polymer-Polymer Composites

Microfibrillar polymer-polymer composites were prepared by melt blending of polypropylene (PP) and poly (ethylene terephthalate) (PET). The blending of the polymers was carried out in a single screw extruder, followed by continuous drawing at a stretch (draw) ratio 5. The stretched blend was converted into polymer-polymer composite by injection moulding carried out at temperatures between the melting points of PP and PET Morphology analysis revealed that the extruded neat blend was isotropic, whereas the stretched blend possessed highly oriented fibrils generated in situ during drawing. The PET fibrils were found to be randomly distributed in the PP matrix of the polymer-polymer composite obtained. The mechanical properties of the injection moulded neat blend and polymer-polymer composite were compared. The tensile and impact properties of the composite were found to be considerably higher than that of the neat blend. The non isothermal crystallization behaviour of the neat blend, stretched blend and the polymer-polymer composite was compared. The oriented PET fibrils in the stretched blend were found to have a greater nucleating effect for the crystallization of PP than the spherical PET particles in the neat blend and randomly oriented short PET fibrils in the polymer-polymer composite.