Application of Unsymmetrical Ureas as a Catalytic Additive for Curing Epoxy Resins (Review)

This paper presents a review of scientific and technical literature on the main production methods, various fields of application, and use of unsymmetrical ureas as an accelerator for the curing processes of epoxy compositions. Mechanisms of reactions between ureas and the widely used latent hardener dicyandiamide are presented, and the characteristics of resulting epoxy resins, as well as prepregs based on them, are considered. The possibility of using substituted ureas as an independent cross-linking agent for epoxy resins is mentioned.