LAUSR

Abstract The effects of blending sequence and residence time on the efficiency of nanosilica as an interfacial compatibilizer of an immiscible blend of polypropylene and ethylene vinyl-acetate (PP/EVA) with unstable droplet-matrix morphology, melt-compounded in a twin-screw extruder, was investigated. Morphological analysis revealed that the nanosilica particles are adsorbed at the blend interface, irrespective of the processing conditions adopted, which is in good agreement with predictions based on the thermodynamic interactions, kinetics of mixing and rheological parameters. It was observed that the effectiveness of interfacial nanosilica in the compatibilization of the PP/EVA blend is greatly dependent on the mixing time, and the blending sequence is less important. The size of the EVA droplets is reduced when PP/EVA blends are processed with longer residence times, and increases with shorter mixing times. The results reported herein and in a previous publication [Polym Test 34 (2014) 175–182] suggest that the interfacial nanosilica layer does, in fact, inhibit the coalescence while at the same time hindering the break-up of EVA droplets during the PP/EVA melt blending, with the net effect being dependent on the magnitude of these two time-related mechanisms.