Repeatable self-healing of an epoxy matrix using imidazole initiated polymerization

For the first time, repeatable self-healing was achieved in a cross-linked epoxy polymer by incorporating 2-ethyl-4-methylimidazole (24-EMI) into the matrix as a latent polymerization initiator. Upon material damage and infiltration of liquid EPON 8132 epoxy monomer healing agent into the crack plane, polymerization occurs in the damaged region with a moderate application of heat in the presence of the latent imidazole initiator. Using tapered double cantilever beam (TDCB) fracture testing, greater than 90% recovery of fracture toughness was observed over multiple healing cycles in samples containing 10 wt% 24-EMI, with up to 11 repeat healing cycles possible. The effect of incorporating the imidazole on the host epoxy fracture toughness, complex moduli and glass transition temperature was also investigated. As imidazole concentration increases, a reduction in glass transition temperature and an increase in fracture toughness of the host epoxy is observed.