STYRENE-ASSISTED MELT FREE-RADICAL GRAFTING OF GLYCIDYL METHACRYLATE ONTO AN ETHYLENE AND PROPYLENE RUBBER

This article deals with the efficiency of using styrene (St) as a como nomer to promote the melt free radical grafting of glycidyl methacryla te (GMA) onto an ethylene and propylene rubber (EPR) in a batch mixer and a corotating self-wiping twin screw extruder. The addition of St t o an EPR/GMA/peroxide system increases not only GMA's grafting yield b ut also its grafting rate. The time required for the EPR/GMA/peroxide system without St to reach a given amount of grafted GMA is at least 1 0 times that needed for the same system in the presence of an equimola r amount of St. For example, about 60 min are required for the EPR/GMA /dicumyl peroxide (composition: 100/3.0/0.3 by weight) to reach 1.5 ph r (parts per hundred resin) GMA (i.e., 1.5 g grafted GMA per 100 g EPR ). The same amount of grafted GMA is reached in < 3 min when 3.0 phr S t is charged to the system. This significant reduction of reaction tim e is crucial for a successful free radical grafting of GMA on EPR in a corotating twin screw extruder, because the residence time in such a machine is typically on the order of 0.5-5 min. (C) 1999 John Wiley & Sons, Inc.