عنوان مقاله [English]
Epoxy systems have many industrial applications because of their excellent adhesion, high chemical and thermal resistance, interesting mechanical and physical properties and so on. Generally, epoxy systems are categorized as two-component and one-component systems. In this report, different kinds of one-component systems, hardeners and accelerators are studied. In single-component epoxy systems, the resin and curing agent have already been mixed together and are supplied as a single product. There is no significant reaction between the resin and curing agent, unless environmental conditions are favorable to trigger a reaction. Several new methods have been developed over the years to provide single-component systems with a long shelf life and good performance characteristics. Among these methods, the most effective and widely used method is the use of latent curing agents especially, dicyandiamide, which providesnot only high mechanical properties, but also a shelf life longer than any othersingle-component curing agents. Curing reaction takes place at high temperatures, when latent curing agents are used. Hence, to achieve a desired curing system which can be activatedat lower temperature, one or more compatible accelerators are required with achosen curing system. The selection of an accelerator depends on the desired final properties. Typically, for a single-component system with the dicyandiamide curing agent, substituted ureas are the most appropriate accelerators. Among substituted urea, 4,4-methylenebis()phenyldimethyl urea A) ()grade isomer) with commercial name of Omicure U-25 has the best performance, since it provides a set of optimized properties.