MELT GRAFTING OF GLYCIDYL METHACRYLATE ONTO POLYPROPYLENE AND REACTIVE COMPATIBILIZATION OF RUBBER-TOUGHENED POLYPROPYLENE

Free radical melt grafting of glycidyl methacrylate (GMA) onto polypro pylene (PP) was studied. The extent of GMA grafting and the molecular weight of the functionalized PP copolymers were controlled by carefull y manipulating various reaction factors, such as monomer concentration , initiator concentration, reaction temperature, and molecular weight of the starting PP homopolymer. The use of a second monomer, styrene, in the grafting process helped to increase GMA grafting further and re duce chain scission, The GMA modified PP copolymer was found to be abl e to reactively compatibilize PP/acrylonitrile-co-butadiene-co-acrylic acid rubber (NBR) blends. Up to an eight-fold increase in the impact energy of the PP/NBR blend was obtained. The compatibilizing capacitie s of the reactive copolymers, in terms of impact energy improvement of the PP/NBR blend, were found not to be exclusively dependent on the t otal concentration of reactive functionalities in the matrix of the bl end. The characteristics of the reactive copolymers, i.e., the extent of functionalization and the molecular weight, were found to have sign ificant influences on the compatibilizing capacity. A large amount of moderately functionalized copolymer offers better compatibilization pe rformance than a small amount of highly functionalized copolymer. A si gnificant drop in impact energy was observed with declining molecular weight of the copolymer.