Effects of the molecular structure of impact modifier and compatibilizer on the toughening of PBT/SBS/PS-GMA blends

摘要

This work aims at studying the toughening process of poly(butylene terephthalate) (PBT) through its blends with styrene-butadiene-styrene block copolymers (SBS), in the presence of poly(styrene-ran-glicydil methacrylate) (PS-GMA) as reactive compatibilizer. High values of impact strength were attained for PBT/SBS blends without the compatibilizer; however, this improvement is achieved for blends with SBS having similar viscosity compared to PBT, at high SBS content (40 wt %) and for blends prepared under specific processing conditions. The efficiency of the in situ compatibilization of PBT/SBS blends by PS-GMA was found to be strongly dependent on the SBS and PS-GMA molecular characteristics. Better compatibilizing results were observed through fine phase morphologies and lower ductile to brittle transition temperatures (DBTT) as the interfacial interaction and stability of the in situ formed compatibilizer are maximized, that is, when the miscibility between SBS and PS-GMA and reaction degree between PBT and PS-GMA are maximized. For the PBT/SBS/PS-GMA blends under study, this was found when it is used the SBS with higher polystyrene content (38 wt %) and with longer PS blocks (M-w = 20,000 g mol(-1)) and also the PS-GMA with moderate GMA contents (4 wt %) and with molecular weight similar to the critical one for PS entanglements (M-c = 35,000 g mol(-1)). (c) 2006 Wiley Periodicals, Inc.