Sunlight-Activated Self-Healing Polymer Coatings

UV light can cause damage to polymer coatings used in transportation, oil, and agricultural industries, requiring costly repair or replacement of the coating. Herein, a self-healing epoxy coating is developed so that UV light activates a desirable autonomous healing response to mechanical damage. The coatings contain a single type of microcapsule with a UV-curable epoxy healing chemistry in the core and a novel UV-protecting shell wall with embedded carbon black particles. Photo-differential scanning calorimetry reveals that up to a 65% degree of protection is provided by the UV-blocking shell wall after UV exposure. The addition of a polyurethane (PU) top coat provides further increase in the level of protection (≈100%). After damage with a scribe and exposure to UV, the presence of healed epoxy is confirmed by confocal Raman and fluorescent spectroscopy. The anticorrosion performance of healed coatings on steel substrates is assessed after exposure to a simulated saltwater solution. The UV-curable, self-healing coating exhibits significantly less corrosion than a control coating with no self-healing ability.