The Effects of Melt Processing Variables on the Morphology and Properties of Injection Molded Polypropylene

Abstract

Controlled variations in melt temperature and injection pressure during the injection molding of isotactic polypropylene tensile bars have been correlated with differences in the skin-core morphology and preferred orientation as observed using optical microscopy and X-ray diffraction. The molding anisotropy has, in turn, been related to systematic variations in tensile yield strength, notched Izod impact strength, and longitudinal shrinkage. The correlation between processing variables and morphology was used to construct a qualitative model for the origin of the skin-core morphology during the filling and packing stages of injection molding.