BASIC FUNCTIONALIZATION OF POLYPROPYLENE AND THE ROLE OF INTERFACIAL CHEMICAL BONDING IN ITS TOUGHENING

A reactive polypropylene (PP) containing oxazoline functional groups w as prepared by the melt grafting of 2-iso-propenyl-2-oxazoline onto a PP homopolymer and used to introduce varying amounts of interfacial ch emical reaction in PP/acrylonitrile-co-butadiene-co-acrylic acid rubbe r (NBR) blends. A technique has been successfully developed to control the rubber particle sizes of PP/NBR blends such that various PP/NBR b lends with the same rubber particle size can be obtained by using diff erent combinations of processing conditions and the amount of interfac ial reaction. It has been found that moderate levels of interfacial ch emical bonding are required for a transition from a brittle to ductile failure to be observed in PP/NBR blends. Blends without any interfaci al chemical bonding showed no improvement in impact energy whereas up to a 13.5-fold improvement in impact energy (notched Charpy test) was observed for reactive blends above the brittle-tough transitions.