Epoxy Curing Agents. I. Imidazoles,
Abstract:
2-Ethyl-4-methylimidazole EMI-24 cures epoxy adhesives at a moderate temperature and imparts high heat resistance to the product. Due to the tendency of EMI-24 to crystallize at room temperature, this study was undertaken to find a suitable replacement. Resins cured with EMI-24, 1-methylimidazole MI-1, and imidazole were compared with respect to bond strength and heat deflection temperature as functions of curing-agent concentration and cure conditions. Results indicate that the physical properties of resins cured with MI-1 and imidazole are comparable with that cured with EMI-24. MI-1 has the advantages of being readily available and of being a liquid at room temperature. A published article on the mechanism of imidazole-cured epoxy resins suggests that the pot life of the adhesive system may be increased by placing deactivating substituents on the imidazole ring. Results of a study of such systems are presented. Author