Preparation of novel soluble poly(ester imide)s containing a trimellitimide moiety and their use as modifiers for aromatic diamine-cured epoxy resin

摘要

Poly(ester imide)s, prepared by the reaction of phthalic anhydride, N-(4-carboxyphenyl) trimellitimide and 1,2-ethanediol, were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with 4,4'-diaminodiphenyl sulfone (DDS). The poly(ester imide)s include poly(ethylene phthalate-co-ethylene N-(1,4-phenylene) trimellitimide dicarboxylate)s (PESIs) having 10, 20 and 30 mol% trimellitimide (TI) units, respectively. PESIs having 10 and 20 mol% TI units were effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt% of PESI (20 mol% TI unit, M_W 19300 g mol~(-1)) led to a 55% increase in the fracture toughness (K_(IC)) of the cured resin (with an increase in flexural strength and modulus) and the modified resin had a particulate morphology. PESI having 30 mol% TI units was not effective because of degradation of the modifier by DDS. The toughening mechanism is discussed in terms of morphological and dynamic viscoelastic behaviour of the modified epoxy resin system.