SELECTIVE CROSS-LINKING REACTION IN POLYMER BLENDS .3. THE EFFECTS OF THE CROSS-LINKING OF DISPERSED EPDM PARTICLES ON THE IMPACT BEHAVIOR OF PP/EPDM BLENDS

The selective dynamic crosslinking reaction by means of the N,N'-m-phenylene-bismaleimide/ poly-(2,2,4-trimethyl-1,2-dihydroquinoline) system was carried out on PP/EPDM blends and its effect on the Izod impact strength (IIS) was investigated. Three series of PP/EPDM combinations were adopted to establish different morphologies. In each series, the EPDM wt% varied from 5 to 30 at 5 wt% intervals. The system crosslinked the EPDM particles selectively without PP degradation and change of morphology. Following the crosslinking, the IIS at 23, -10, and -30 degrees C increased in all blends, and the critical EPDM wt% at 23 degrees C necessary to cause the dramatic IIS increase was lowered. The increase in interfacial adhesion is considered to be the most important factor necessary for the improvement. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM were also considered to contribute to the improvement in the IIS. Impact fracture energy absorption can thus be changed by adjusting the magnitude of the interfacial adhesion by the dynamic crosslinking even at essentially the same morphology. (C) 1995 John Wiley and Sons, Inc.