Autonomic healing of epoxy vinyl esters via ring opening metathesis polymerization

A materials system for autonomic healing of epoxy vinyl esters is demonstrated. The system is comprised of wax microspheres containing Grubbs' catalyst and microcapsules containing exo-dicyclopentadiene (DCPD) embedded together in an epoxy vinyl ester matrix. Healing is triggered when damage in the form of a crack ruptures the microcapsules, causing DCPD to be released into the crack plane where it comes in contact and mixes with the catalyst microspheres initiating ring opening metathesis polymerization (ROMP). The chemical compatibility of the catalyst with the matrix is investigated and wax protection of the catalyst via microspheres of a sufficient size (34-98 mu m) is shown to provide a suitable barrier for protecting the catalyst from free radicals generated in situ during the curing of the epoxy vinyl ester resin. Wax protection of the catalyst also allows uninhibited curing of the matrix to proceed at room temperature. Concentration of self-healing components is varied with a view towards optimization of the recovery of virgin mechanical properties. Efficient self-healing is observed with microspheres that are smaller than those used in previous polymer matrices. Significant recovery of virgin mechanical properties is observed within 2.5 min of healing time at room temperature and the mechanical properties of healed samples after 24 h of healing time match those of existing ROMP-based self-healing systems.