Fracture behavior of a self-healing, toughened epoxy adhesive

A self-healing, toughened epoxy adhesive is demonstrated based on a commercial structural adhesive film. Self-healing is achieved via embedded microcapsules containing dicyclopentadiene monomer and solid particles of bis(tricyclohexylphosphine)-benzylidine ruthenium (IV) dichloride (Grubbs') catalyst. Recovery of fracture toughness is assessed through fracture testing of width tapered double cantilever beam (WTDCB) specimens. Healing efficiencies as high as 58% were achieved for 6.6 wt% DCPD microcapsules and 10 mg Grubbs' catalyst. However, virgin fracture toughness is reduced with the addition of ca. 117 mu m diameter microcapsules as a result of suppression of the damage zone as revealed by transmission optical micrographs. The uniform dispersal of microcapsules throughout a rubber toughened epoxy adhesive formulated using EPON 828, piperidine and CTBN alleviated the suppression effect and demonstrated retention of virgin fracture toughness of adhesives. (c) 2013 Elsevier Ltd. All rights reserved.