Self-healing epoxy coatings curing with varied ratios of diamine and monoamine triggered via near-infrared light

Light responsive self-healing capability offers polymer coatings the opportunity to heal surface scratches in a localized, non-contact, and remote manner. A near-infrared (NIR) light (808 nm) responsive self-healing coating is reported here, using epoxy and carbon black as coating matrix and photothermal filler, respectively. The chemical structure and property of the prepared epoxy coatings are tailored by changing the ratio of m-xylylenediamine as diamine and 3,5-bis(trifluoromethyl) benzylamine as monoamine. Carbon black is subsequently incorporated into the coating with the optimized thermally induced self-healing ability to achieve good photothermal effect, correspondingly transferring the thermally triggered healing to the light responsive repairing. The results indicate that with the gradual replacement of diamine with monoamine, the epoxy network having lower crosslink density and glass transition temperature (T_g) is achieved, offering sufficient chain mobility for thermally induced healing. A small amount of CB (up to 1.0 phr) provides the coating good photothermal effect under NIR light. Upon exposed to NIR light of 1.2 W cm⁻² for only 3 min, efficient healing is achieved. The recovery of the filler distribution on the healed region and the restoration of the anti-corrosion property are finally demonstrated. The combination of photothermal filler into tailored epoxy network via changing the ratio of diamine and monoamine provides a convenient approach to heal scratches of coatings via NIR light.