Autonomic Healing of Epoxy Vinyl Esters via Ring Opening Metathesis Polymerization

Abstract

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 μm) 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.

Self Healing Polymers and Composites

“…In epoxy, healing has been achieved with two different catalysts, Grubbs' catalyst (Brown et al 2002(Brown et al , 2004(Brown et al , 2005bJones et al 2006Jones et al , 2007Mauldin et al 2007;Rule et al 2005;White et al 2001) and tungsten hexachloride (Rule 2005). The former approach has also been successful in a vinyl ester matrix (Wilson et al 2007). Another healing system that has been successfully integrated in vinyl ester is based on an encapsulated organotin catalyst and a phase-separated healing agent (Cho et al 2006).…”

Microcapsule-based self-healing materials

“…For example, Biggs and coworkers incorporated the healing system of Grubbs' catalyst/DCPD capsules into PMMA-based bone cement [55,56]. Wilson et al and Chipara et al imparted self-healability to epoxy vinyl ester [57] and polystyreneblock-polybutadiene-block-polystyrene (PS-b-PBD-b-PS) [58] through the application of the same healing system. Moll et al [59] further prepared self-healing glass fiber-reinforced epoxy composite taking advantage of the Grubbs' catalyst-DCPD pair.…”

Self healing in polymers and polymer composites. Concepts, realization and outlook: A review

“…The two-component healant is able to take effect in the woven glass fabric/epoxy composite laminates [63,66]. The group of White et al, the pioneer in developing self-healing polymeric materials, systematically investigated self-healing strategy based on ring opening metathesis polymerization (ROMP) of microencapsulated dicyclopentadiene (DCPD) and reported a series of important findings [55,[67][68][69][70][71][72][73][74][75][76][77][78].…”