Influence of electron beam irradiation on the impact properties of polystyrene/EPDM rubber blends

The influence of electron beam (EB) irradiation on the impact properties of compatibilized polystyrene/ethylene-propylene-diene-monomer (PSIEPDM) blends was studied. The change in impact value upon irradiation proved to be strongly dependent on the type of compatibilizer used. Using a polystyrene/polybutadiene (SB) diblock copolymer as a compatibilizer, a twofold increase in Izod value could be achieved upon irradiation. Irradiation of a blend using a polystyrenel ethylene-propylene (SEP) copolymer as a compatibilizer resulted in a decrease in impact strength. These observations can be related to aradiation induced increase in interfacial adhesion in case of the SB copolymer, which does not occur for the SEP copolymer. Due to the abundance of double bonds in the SB copolymer, this copolymer reacts very fast upon irradiation and may co-crosslink with, or graft onto the EPDM phase. For the SEP copolymer erosslinking occurs only at much higher doses and is (partly) overruled by chain scission and consequently the adhesion between matrix and dispersed phase will hardly change. This view is supported by analytical methods as FT-IR and NMR as well as from Tg measurements.