POLYCARBONATE-EPOXY SEMIINTERPENETRATING POLYMER NETWORK .2. PHASE-SEPARATION AND MORPHOLOGY

Bisphenol A-based epoxy resin (DGEBA) was modified with bisphenol A po lycarbonate (PC), by either a physical or chemical process, and therma lly cured with 4,4'-diaminodiphenyl sulfone, tetraethylenepentamine, a nd anhydride. The phase separation in the PC/epoxy blends was controll ed by varying the composition, and the PC-epoxy reaction, and utilizin g curing agents of different reactivity. A single phase morphology was achieved by accelerating the curing reaction, or introducing PC-epoxy reaction, or eliminating crystallization of PC. Under certain conditi ons, PC spherulites are able to form, in company with the formation of epoxy networks. Curing of the epoxy resin modified the crystallizatio n mechanism, the melting behaviour and the morphology. The nuclei are likely to be pre-existing high molecular weight PC chains and are form ed by the special interaction between PC molecules and the primary net work. Low molecular weight epoxy resins increase the crystallization r ate. The internal fractionation changes by PC chain scission during th e melt blending process has an important influence on the crystallizat ion. The spherulite morphology fixed by semi-IPN structure subjected a loss of order by annealing. It is suggested that hydrogen bonding and graft reaction in this kind of PC/epoxy semi-IPN is the key to contro lling phase separation and morphology. Copyright (C) 1996 Elsevier Sci ence Ltd.