The effect of aging on synthesis by the graft copolymerization of styrene onto random ethylene-propylene-diene monomer with benzoyl peroxide (BPO) as the initiator is described. Results showed that yields of graft copolymer are increased in the first 10 min. After 10 min, the total polymer produced has a maximum at about 25 min. However, the portion of the graft copolymer is decreased and the portion of the pure polystyrene is increased. In addition, the influence factors, such as reaction time, temperature, BPO concentrations and styrene concentrations, effect of solvents on the extent of graft copolymerization were discussed. The extent of grafted copolymerization was verified by hexane and acetone Soxhlet (solvent extraction). (c) 2006 Wiley Periodicals, Inc.