Study On Synthesis And Properties Of Novel Latent Curing Agents For Epoxy Resin

Latent curing agent was mixture of curing agent with epoxy resin that could be stably stored for a relative long period at room temperature, and rapidly cured by heat, light, pressure, and others. More and more attention has been devoted to the latent curing agent which has become high-light in the field of epoxy resin adhesive. New kinds of modified curing agents and new technology had appeared one after another and been used widely.In this paper, a novel series of modified dicyandiamide derivatives and several kinds of modified imidazole or imidazoline derivatives were synthesized, which acted as latent curing agent for epoxy resin. The structures and properties of products were characterized by melting point, FT-IR and ~1H NMR. Combining with the results of the curing experiments and the tests of storage period, several good latent curing agents that possess improved curing performance and long storage life at room temperature have been selected. At the same time, technological parameters and conditions of the synthesis had been studied. The factors, such as ratio of material, temperature and time of reaction and so on, influencing on the purity, yield, curing characteristics and stationary in storage period of the products, were discussed. Moreover, suitable conditions of the synthesis were determined.Several one-component epoxy resins adhesive, in which a few modified dicyandiamide derivatives acted as latent curing agent, were obtained. Curing characteristics of these latent curing systems containing modified dicyandiamide were studied by DSC and FT-IR. The results showed that the modified dicyandiamide had higher reactivity in moderate temperature than dicyandiamide. Besides, suitable ratio of the curing system, curing temperature and curing time had been obtained. Technological conditions of curing reaction were optimized. And the test of tensile shear strength showed that they had good adhesive performance. Moreover, the latent curing system possessed a long storage life and good curing properties in moderate temperature. In addition, curing reaction kinetics and mechanism of epoxy resins adhesive had been investigated.