MELT FREE-RADICAL GRAFTING OF GLYCIDYL METHACRYLATE ONTO POLYPROPYLENE

This paper concerns free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) in the molten state carried out in a batch mixer. This free-radical grafting proceeds very rapidly as it goes to completion within two to three minutes at 200 degrees C. The grafting yield of GMA alone is low and it is greatly enhanced upon addition of styrene as a second monomer with a reduced chain degradation of PP. Homopolymer and copolymer of GMA formed during grafting were quantified. It is suggested that in the presence of styrene, the dominating grafting mechanism is that styrene reacts with the PP macroradicals to form more stable styryl macroradicals which then react with GMA to form GMA-grafted PP. The rate of this reaction is much greater than that between the PP macroradicals and GMA. Unlike grafting of mixtures of maleic anhydride and styrene, which is dictated primarily by formation of a charge transfer complex, free-radical grafting of GMA in the presence of styrene follows a random copolymerization process.