SELF-HEALING COATING HEALED WITH A VISCOELASTIC SUBSTANCE

secondary crack free A protective coating is used to protect surface of a material from various deterioration factors. When cracks form and propagate in the coating, water, chloride ion, and carbon dioxide would penetrate through the cracks. This results in the deterioration of the material, leading to reduction in its serviceability. If the protective coating has self-healing ability, it would effectively protect the materials from the deterioration. In this work a capsule-type self-healing protective coating has been developed using vegetable oils as healing agent. Healing-agent-loaded microcapsules are embedded in a coating matrix to obtain a self-healing protective coating. Upon damage-induced cracking, the microcapsules are ruptured by the propagating crack fronts, resulting in release of the healing agent into the crack by capillary action. A healing reaction occurs by atmospheric oxygen, generating a viscoelastic substance. The self-healing coating was evaluated as protective coating for steel, and it was demonstrated that our system has good self-healing capability. In conventional capsule-type self-healing systems, healing reactions generally produce hard solids, so the systems are considered to be vulnerable to regeneration of cracks in the healed region. Furthermore, the regenerated cracks can not be healed because healing agent is consumed in the first healing process. It should be noted that our new system can effectively prevent the coating from regeneration of cracks in the healed region (Figure 1)