MICROSTRUCTURE AND PHYSICAL PROPERTY CONTROL OF INJECTION-MOLDED POLYPROPYLENE

Isotactic polypropylene (IPP) (melt flow index of 3.1 g/10 min) was in jection moulded to investigate processing-physical property relationsh ips. Both conventional injection moulding and shear controlled orienta tion injection moulding (SCORIM) were used for the production of mould ed bars. SCORIM mouldings were shown to exhibit more pronounced molecu lar orientation than conventional mouldings. There was typically a 75% increase in the stiffness of IPP following the application of SCORIM. A morphology indicative of chain extension in SCORIM mouldings was re vealed by TEM studies and the relative proportion of alpha, beta and g amma phases was markedly dependent on moulding method, with gamma-phas e being detected only in SCORIM mouldings.