| Abstract: | Infrared and NMR data on tertiary amine-catalyzed, dicyandiamide—epoxy resin (and model compound) systems have been utilized to elucidate the mechanism of the curing process. The early exothermic curing reaction is shown to be ring opening of the resin epoxy groups by dicyandiamide imino and amino anionic species, giving rise to N-alkyl cyanoguanidines; a minor amount of polyether formation also occurs at this time. After the exothermic reaction is essentially complete at <90°C., a slow, high temperature (110–200°C.) addition of hydroxyl hydrogen across the nitrile triple bond occurs, giving rise to an imino ether which then rearranges to the guanyl urea. |
