Intelligent Self-Healing Coatings: Investigating the Role of Self-Healing Kinetics at the Delaminating Interface

The ultimate aim in the development of novel self-healing coating systems is to heal larger defects inflected into the coating reaching down to the metal, such as deep scratches. For this great amounts of self-healing agents have to be transported from the coating system to the defect site. This is a considerable challenge, especially since the self-healing agents to be stored in the coating system should safely stay inside it as long as they are not needed and they should still be available and active even after years of exposure. This requires reliable storage and very case-selective release mechanisms. At the same time, once the agents are released they should reach the defect site as fast as possible and in sufficient amounts. In many self-healing concepts found in the literature this is achieved by release through the coating surface. The transport to the defect site then occurs through the electrolyte. However, in most cases the self-healing coating will be covered by other coatings, such as e.g. for providing color or scratch resistance. Then the transport has to occur laterally. The best option for this is transport along the delaminating interface, as was recently shown for the release of inhibitors from conducting polymer based capsules incorporated in a PVB matrix [1, 2]. However, for really self-healing coating systems the transport of the active agents to the defect site will be impeded, if the delamination is stopped too early by a too fast self-healing at the interface before the defect site is healed [3]. First results of a more in-depth study of this problem will be shown. An important issue is to assess the degree of self-healing at the buried interface. For this a novel approach for studying the degree of interfacial degradation will be presented.

References

[1]A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder
Redox-Responsive Self-Healing for Corrosion Protection
Advanced Materials 25(48)  (2013) 6980-6984

[2]L.P. Lv, Y. Zhao, N. Vilbrandt, M. Gallei, A. Vimalanandan, M. Rohwerder, K. Landfester, D. Crespy,
Redox Responsive Release of Hydrophobic Self-Healing Agents from Polyaniline Capsules
J. Am. Chem. Soc. 135 (2013) 14198-14205

[3]T.H. Tran, A. Vimalanandan, G.Genchev, J. Fickert, K. Landfester, D.Crespy, and M. Rohwerder Regenerative Nano-Hybrid Coating Tailored for Autonomous Corrosion Protection
Advanced Materials, accepted