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)(I-MesH(2)) (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, K-IC. The percentage of healing was calculated as the ratio of K-IC 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. (c) 2012 Elsevier Ltd. All rights reserved.