Silane modified epoxy coatings with low surface tension to achieve self-healing of wide damages

Self-healing behavior of polymer coatings consists of two steps: crack closure and crack repair. Shape-memory effect, conformational transition of polymer chains, and water-induced flowability were reported on crack closure as the preliminary and necessary step. All of them, however, cannot achieve the trade-off between healing from wide damage and satisfied properties. Here, we prepared silane modified epoxy coatings, which achieved the self-healing of cracks with width of 300 μm upon heating and good mechanical properties. Furfurylamine (FA) and furfuryl glycidyl ether (FGE) were reacted with diglycidylether of bisphenol A to prepare oligomers with furan groups as side and terminal groups, which created reversible crosslinking bonds based on Diels-Alder reactions with maleimide groups from bis(4-maleimidophenyl)methane. (3-aminopropyl)triethoxysilane (APTES) was also involved to reduce the surface tension of coatings and to offer irreversible crosslinking bonds that ensured the coating stability during heating. We fully studied the effects of the ratio of APTES and FA (1:9, 2:8, 3:7, and 4:6) on the chemical structures, molecular weight, and thermal properties of oligomers, as well as the chemical structures, surface structures, mechanical properties of coating materials. By increasing the ratio of APTES and FA, the surface tension of the coating was gradually decreased until a critical ratio of 3:7. All coatings possessed similar and good mechanical properties. The self-healing behaviors were found to be dominated by the competition among shape-memory effect, surface tension driven flow, and viscosity, which were related to coating network structures. Thick coatings also facilitated the crack closure and healing performance. Compared with the coating without silane modification, the self-healing behavior was improved, the mechanical properties were maintained, and the anti-corrosion properties were deteriorated.