Reactive processing of polymers: Melt grafting of glycidyl methacrylate onethylene propylene copolymer in the presence of a coagent

Glycidyl methacrylate (GMA) was grafted on ethylene-propylene copolymer dur ing melt processing with peroxide initiation in the presence and absence of a more reactive comonomer (coagent), trimethylolpropane triacrylate (Tris) . The characteristics of the grafting systems in terms of the grafting reac tion yield and the nature and extent of the competing side reactions were e xamined. The homopolymers of GMA (Poly-GMA) and Tris (Poly-Tris) and the GM A-Tris copolymer (GMA-co-Tris) were synthesized and characterized. In the a bsence of the coagent, high levels of poly-GMA, which constituted the major competing reaction, was formed, giving rise to low GMA grafting levels. Fu rther, this grafting system resulted in a high extent of gel formation and polymer crosslinking due to the high levels of peroxide needed to achieve o ptimum GMA grafting and a consequent large drop in the melt index (increase d viscosity) of the polymer. In the presence of the coagent, however, the g rafting system required much lower peroxide concentration, by almost an ord er of magnitude, to achieve the optimum grafting yield. The coagent-contain ing GMA-grafting system has also resulted in a drastic reduction in the ext ent of all competing reactions, and in particular, the GMA homopolymerizati on, leading to improved GMA grafting efficiency with no detectable gel or c rosslinking. The mechanisms of the grafting reactions, in the presence and absence of Tris, are proposed. (C) 2000 John Wiley & Sons, Inc.