Monitoring Fluorescence Colors to Separately Identify Cracks and Healed Cracks in Microcapsule-containing Self-healing Coating

Abstract

We developed a system involving an extrinsic self-healing coating to identify cracked and healed regions by their yellow fluorescence and blue fluorescence, respectively. This system consisted of a top coating, an epoxy matrix resin containing a yellow fluorescent dye, and a microcapsule. This microcapsule in turn consisted of a healing agent, a blue aggregated-induced emitting luminogen, and a photo-initiator, as well as poly(urea-formaldehyde) as a shell material. Embedding the self-healing coating with a 25 mass% of microcapsules yielded the most efficient fluorescence detection and healing of the damaged region. Scratched and healed regions were successfully detected using our system under UV irradiation as well as under a one sun condition similar to sunlight. The blue fluorescence of the healed region was easily seen from 2 m away.