A latent, micronized accelerator based on a substituted urea. Its prominent use is preferably in combination with the highly latent curing agents of the Dycure series DCD in thermosetting epoxy resin formulations. Dycure U200-11 is widely used as a latent accelerator in thermosetting epoxy resin formulations. Its use is particularly suited in combination with micronized dicyandiamide [Dycure 8]. In thermosetting epoxy/dicyandiamide (DICY) formulation, the DICY is hardener which provides good processing, outstanding electrical, mechanical features, and extended shelf life. Nevertheless, this system needs elevated curing temperature as close as 200 áµ’C, which is high for most applications. Therefore, it is demanding to use accelerators to diminish the curing temperature significantly, whilst not sacrificing the shelf life of composite. As a blocked accelerator the Dycure U200 facilitate the epoxy-dicyandiamide reactions resulting in a long shelf life material. Subsequent thermal activation, it offers with fast curing and high cross-linking density. Under the heat Dycure U200 decomposes to generate active species such as dimethylamine and isocyanate groups. These active groups could accelerate the epoxies curing process and also forming additional linkages as a result of reaction with epoxy groups in the network. In many one component thermosetting epoxy resin formulations, Dycure U200 is extensively used as accelerator to activate dicyandiamide curing agents for:
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