Latent CO2-Protected N-Heterocyclic Carbene-Based Single-Component System-Derived Epoxy/Glass Fiber Composites

Epoxy-based fiber-matrix composites based on a single-component curing system with pot times >>two weeks are described. Bisphenol-A-diglycidyl ether and hexahydrophthalic anhydride were used as epoxy matrix precursors; 1,3-dicyclohexyl-3,4,5,6-tetrahydropyrimidinium carboxylate (6Cy-CO2) was used as latent pre-catalyst. Glass fiber-reinforced epoxy resins were obtained both via thermal curing under air and under vacuum-assisted resin infusion conditions. The high quality of the resulting composites and the absence of any air inclusion were confirmed by DSC and x-ray tomography. Rheological and kinetic data revealed that the 6Cy-CO2-based systems allow for an advanced processing and outrival commercial amine-based hardeners in terms of speed of curing.