Curing of epoxides. Reaction of dicyanodiamide with phenylglycidyl ether

Abstract

AbstractCuring of epoxy resins with the latent hardener 1‐cyanoguanidine (dicyanodiamide) was studied using a model system. Phenylglycidyl ether was reacted with 1‐cyanoguanidine in the presence of benzyldimethylamine as a catalyst in a solution in 2‐methoxyethanol. The reaction kinetics was followed by means of HPLC and IR spectroscopy. Some of the reaction products were isolated by semipreparative HPLC and identified.The influence of temperature and of the initial ratio of reaction components on the reaction mechanism was studied. Three partial reactions were found: a) addition of the amino groups of 1‐cyanoguanidine to the epoxide, which then initiates the reaction of OH groups of the addition products, b) with the C≡N group, or c) with the epoxide (etherification). The relative extents of the latter two reactions increase with conversion. The reaction of the nitrile group is preferred at high temperatures but depressed in the presence of excess epoxide in the reaction mixture when etherification prevails.