Repeatable self-healing of an epoxy matrix using latent 2- Ethyl-4-methylimidazole catalyst

Microvascular based self-healing schemes for autonomic repair of damaged composite materials show promise over microcapsule based healing schemes, as vascular systems provide the possibility of filling large damage volumes over multiple healing cycles. To date, many of the studies on microvascular based self-healing materials have used a two-part, stoichiometrically based set of healing agents for repeatable self-repair [1-5], However, in these studies, proper stoichiometric mixing of the two components required a combination of complex pumping schemes, mechanically induced stimulation, and/or a highly interpenetrated network of channels. In this work we present an alternative method of repeatable self-repair in an epoxy based polymer system using initiator triggered anionic addition polymerization of an epoxy resin. Latent initiator functionality is built into a typical epoxy matrix by the addition of 2-ethyl-4-methylimidazole (24-EMI) into the matrix material during processing. Self-healing is achieved by the release of liquid epoxy monomer into the crack whereby polymerization of the monomer is initiated thermally in the specimen through a moderate application of heat and presence of the latent initiator. Evaluation of the healing potential is performed using tapered double cantilever beam specimens and our results demonstrate that repeatable 100% recovery of mode one fracture toughness is achieved over multiple healing cycles with 10 wt% 24-EMI incorporation. These studies are a prelude to the adoption of this system in a vascular fiber reinforced composite for repeatable healing of large internal damage in structural components.