| Abstract: | The bifunctional epoxides bisphenol A diglycidyl ether (BADGE) and hexahydrophthalic diglycidyl ester (HHDGE) as well as the monoepoxides phenyl glycidyl ether (PGE) and cyclohexane carboxylic acid glycidyl ester (CHGE) were cured with hexahydrophthalic anhydride (HHPA) in the presence of benzyldimethylamine (BDMA) or 1-methylimidazole (1-MI) as catalysts at 100–140°C. Investigations of the curing kinetics gave sigmoidal-shaped curves with marked induction periods. IR analysis of the cured products revealed that the propagation proceeds not only by the esterification reaction of epoxide with anhydride but also by chain anhydride formation by the reaction of carboxylate with anhydride groups. 13C-NMR investigations of the soluble polymers showed that most of the peaks resulting from double bonds could not be assigned to structures formed by initiation reactions that had previously been proposed for the anhydride curing of epoxides. In analogy to a postulated mechanism for the decarboxylation condensation of HHPA alone in the presence of tertiary amines, it is proposed that an isomerization product of HHPA is one of the molecules that initiate the curing reaction. |
