Self‐Healing Epoxy Coatings via Focused Sunlight Based on Photothermal Effect

Abstract

Epoxy coatings which can be healed via photothermal effect from focused sunlight are reported. The diamine of m‐xylylenediamine (MXDA) and monoamine of 4‐(heptadecafluorooctyl)aniline (HFOA) are reacted into the diglycidylether of bisphenol A (DGEBA) network. Via gradual replacement of MXDA with HFOA, the glass transition temperature and crosslinking density of the epoxy network are tuned to achieve the thermally induced healing based on chain diffusion and reentanglement. Aniline black (AB) with well absorptivity for sunlight is used subsequently as the organic photothermal compound, transferring the thermally induced healing into a sunlight responsive one. A common handheld magnifier, which can focus natural sunlight to the required power density (0.6–0.9 W cm−1), is used to successfully heal one cracked coating in outdoor circumstance. This study provides a potential approach to achieve the convenient, precise, and timely healing for outdoor epoxy coatings.

Thermally-Induced Self-Healing Behaviors and Properties of Four Epoxy Coatings with Different Network Architectures

“…As shown in the FTIR spectra ( Figure 2 a), no evident peak was observed at 916 cm −1 for dense irreversible Network I and loose irreversible Network III, indicating the complete curing of unreacted epoxy groups with the amine groups from MXDA [ 28 , 29 , 30 , 31 ]. The curing conditions for the dense irreversible Network I were 60 °C for 2 h, 100 °C for 3 h, and 140 °C for another hour, as presented previously [ 9 , 32 ]. We have shown in a previous report that a sufficient conversion of epoxy groups over 93% occurred within the first hour of the reaction between DGEBA and MXDA at 60 °C [ 32 ].…”

“…The curing conditions for the dense irreversible Network I were 60 °C for 2 h, 100 °C for 3 h, and 140 °C for another hour, as presented previously [ 9 , 32 ]. We have shown in a previous report that a sufficient conversion of epoxy groups over 93% occurred within the first hour of the reaction between DGEBA and MXDA at 60 °C [ 32 ]. Therefore, the synthesis condition for Network III here (60 °C for 12 h) was also considered to ensure the complete curing reaction.…”

“…Network II presented a complete gap closure in 40 s, facilitating the second repair step and causing a crack disappearance after only 80 s. Direct heating at a high temperature triggered an immediate gap closure by reverse plasticity, while the tight contact of crack surfaces allowed Oligomer I resulting from rDA reaction to diffuse into the opposite crack surface, preventing the occurrence of dewetting and ensuring the complete crack repair. Based on an image analysis method as described previously [ 32 ], the healing efficiency was calculated to be 91 ± 6%, suggesting a sufficient crack repair. Similarly, Network IV also exhibited a gap closure in 40 s, while the crack to some extent disappeared after 80 s. Since less reversible bonds were incorporated, the complete crack repair was not achieved.…”

Microencapsulation of oil soluble polyaspartic acid ester and isophorone diisocyanate and their application in self‐healing anticorrosive epoxy resin

“…There were various methods to against the metallic materials corrosion, one of the common and useful ways was coating a protective layer on metal surface. As physical barrier, organic coating could prevent the contact of metal with aggressive media and promote the corrosion protection . Since the self‐healing composites emerged a couple of decades ago, self‐healing coatings had received considerable attention due to their intellectualization and efficiency in steel anticorrosion application .…”

The influence of size and healing content on the performance of extrinsic self‐healing coatings

“…In recent years, several strategies for self-healing have been employed such as the release of healing agents, reversible bonds, and nanoparticles with the ability to migrate. [19][20][21][22][23] It has been proved that the release of the healing agent is the most well-studied method among the other. [24][25][26] The release of the healing agent is an autonomic self-healing process based on the encapsulated active agents that is, catalysts, monomers, hardeners, and dyes.…”