An autonomous self-healing system based on ROMP of norbornene dicarboximide monomers

This work reports the first example of an autonomous self-healing process at ambient temperature based on the ROMP of mono- and di-functional norbornene dicarboximides. The mixture of the mono- and di-functional norbornene dicarboximide monomers was successfully encapsulated by a method involving urea-formaldehyde and used as healing agents. All specimens were prepared by mixing microcapsules (10 wt%) Grubbs' ruthenium initiators RuCl2(=CHPh)(PCy3)2 (G1) (5 mol%) or RuCl2(=CHPh)(PCy3)(IMesH2) (G2) (2.5 mol%) with the epoxy resin components. Fracture tests were carried out at ambient temperature on all specimens using the compact tension geometry in order to determine a value for the critical stress intensity factor, KIC. The percentage of healing was calculated as the ratio of KIC after healing to that of the virgin test. It was found that while the specimens containing healing agent of high viscosity comprising of just a mixture of mono- and di-functional norbornene dicarboximide monomers required clamping to initiate healing, those containing healing agent of low viscosity comprising a mixture of these two monomers and 25 wt% of ethylidene norbornene, as a reactive diluent monomer, healed unclamped. The healing efficiency of 33% was observed and this developed between 11 and 24 h.