EPOXY MODIFIER BLOCK COPOLYMERS

The curing of epoxy resins with anhydrides in the presence of dihydroxyl-terminated polyester or polyether modifiers produces block copolymer structures in which one ″block″ is the crosslinked epoxy/anhydride network and the other block is the linear modifier segment. The morphology of the cured system is dependent upon modifier molecular weight. The critical molecular weight of polycaprolactone and poly(propylene oxide) is 3000-5000. Below this level, single morphological phase systems are obtained, but two microphase systems result above this level. Two-phase systems display a superior balance of heat distortion temperature and impact strength, thus providing tough systems with greater elevated temperature capabilities than are obtained with single-phase systems.