Mechanism of the dicyandiamide/epoxide reaction

A mechanism is proposed for the dicyandiamide (dicy) cure of epoxy resins based on theanalysis of products formed by the reaction of a monofunctional epoxide with dicy and with cyanamide.Products were isolated from the uncatalyzed reaction mixtures using preparatory liquid chromatography andwere characterized by FTIR, NMR, mass spectrometry, and elemental analysis. Both linear dicy/epoxideadducts and cyclical species were identified and the mechanism of the cyclization reaction was delineated.A mechanism for carbonyl generation during the later stages of cure was also found.