Thermally Controlled Acceleration of Epoxy Resin Curing through Polymer-Bound Imidazole Derivatives with High Latency

Imidazole-containing polymeric accelerators were synthesized through free-radical polymerization and applied in the curing of diglycidyl ether of bisphenol A resin with the hardener dicyandiamide. Reactivity and storage stability were followed via differential scanning calorimetry, and an increased pot life was observed after incorporation into polymers. Depending on the employed monomers and composition, the compatibility with epoxy resin was adjusted and the storage stability thereby improved, while a high reactivity is retained under curing conditions. Microscopy imaging showed the dissolution of the polymeric accelerators in epoxy resin above a critical temperature enabling a high reactivity. The best performing accelerator was then applied in an epoxy adhesive film formulation. The strength of the bonding of stainless-steel test bodies was examined in a lap shear test showing superior long-term stability while maintaining efficient acceleration of this type of polymeric accelerator for adhesive applications.