Build a bridge from polymeric structure design to engineering application of self-healing coatings: A review

From civil to industrial engineering, coating can be found almost everywhere. In practical application, the change of external environment causes coating cracks, resulting in the deterioration of performance and/or functions. When damage occurs, it not only increases replacement cost, but involves safety issues as well. Although endowing coatings with self-healing capability can eliminate coating cracks, there is still a big gap between academic research and applications. In this review, we summarize research progress of intrinsic self-healing coatings in recent years, focusing on structural design of polymers, filler components and dispersion mechanism, to provide thoughts for the exploitation of potential applications of self-healing composite coatings with high performance and multi-functions. Intrinsic self-healing coatings can only be repaired after cracks are closed, that is, self-healing behavior consists of two stages: crack closure and healing. Therefore, closing and healing mechanisms of reported self-healing polymeric structures are introduced. In addition, the relationship between the choice of functional fillers and self-healing performance is focused for the creation of high performance and/or multi-functions self-healing composite coatings. The development prospect of remote healing composite coatings is prospected as well. Finally, the dispersion mechanism of fillers in coatings is discussed to construct self-healing composite coatings composed of polymers and fillers, which can realize the characteristics of high performance, multi-functions and self-healing.