Water resistant reactive microcapsules for self-healing coatings in harsh environments

Double-shelled microcapsules containing liquid 4,4′-bis-methylene cyclohexane diisocyanate (HMDI) with outstanding water resistance are successfully synthesized via combination of interfacial and in-situ polymerization reactions in an oil-in-water emulsion. The diameter and shell thickness of microcapsules increased under lower agitation rate. The relative residue of core content of microcapsules remains more than 90% after 24 days in both ambient open air and water. Manually scratched polymer coatings with both fresh and conditioned microcapsules showed satisfactory anticorrosion performance in salt water via self-healing functionality. In addition, self-healing coatings with fresh microcapsules after immersion in ambient water for 30 days still possessed superior anticorrosion performance.