Monitoring Fluorescence to Identify Cracks in Self-Healing Coated Fabric of Thermal-Induced Microcapsules

The self-warning and thermal-induced self-healing microcapsules were fabricated by the interfacial in situ polymerization process, which consists of SiO2 as the shell material and epoxy resin, a thermal initiator, and a fluorescent agent as the core materials. The squeegee coating method was used to prepare the self-healing self-warning PVC-coated fabric. The microcapsules have a core–shell structure with an average particle size of 1.5 μm and a high sphericity with a coverage rate of 77% and excellent thermal stability below 320 °C. The PVC coating agent has good wettability with the microcapsules with a contact angle of 34.6 ± 0.9°. When cracks appear on the surface of the coated fabric containing microcapsules, the fluorescent agent and repair agent (epoxy resin and thermal initiator) will then flow out from the broken microcapsules and fill the cracks owing to the great wettability of the PVC coating agent with a contact angle of 44.2 ± 1.1°. Under UV light, the cut displays a yellow fluorescence line, indicating the location of the damage. After filling the cracks, the epoxy resin polymerizes with the thermal initiator at 120 °C. When the heating time reaches 6 h, the cuts in the fabric are healed, and the strength of the coated fabric reaches 699 N, thereby matching the original strength of 713 N before cutting.