Study of epoxy compounds. Part I. Curing reactions of epoxy resin and acid anhydride with amine and alcohol as catalyst

Abstract

Abstract The curing reaction of an epoxy resin and acid anhydride with an amine and/or alcohol was studied kinetically. No etherification reaction occurred at 70–140°C. and the initial reaction rate was proportional to the concentration of epoxide, acid anhydride, and catalyst (tertiary amine or alcohol). The apparent activation energies of the reaction in two systems of epoxy resin–hexahydrophthalic anhydride/triethanolamine (0.5 wt. %) were obtained as 14.1 and 14.4 kcal./mole. The effects of the substitution R of the tertiary amine NR 3 or alcohol R 3 COH as catalyst on the curing reaction of the epoxy resin and acid anhydride were studied. The polar reaction constant ρ p for amines, obtained negatively, indicates that electron‐repelling substituents of NR 3 increase the curing rate; ρ p for alcohols, obtained positively, indicates that electron‐withdrawing substituents of R 3 COH increase the rate of curing reaction. These results supported the proposed curing mechanism better.