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In a previous study, self-healing polyurethane coatings with microcapsules containing healing agents have been developed for the protection of metal from corrosion. At the initial stage of the development of these coatings, we synthesized the microcapsules containing healing agents by adding organic solvents to inhibit the solidification of the whole capsule. In this study, the structure of the capsules formed with different solvents, such as chlorobenzene, toluene and xylene was examined. We also evaluated the self-healing ability of coatings with these capsules after damaging the coating by scratching. The amount of healing agents contained in capsules depends on the kind and the amount of solvents added. In the capsule formed with 20 or 50 wt%-chlorobenzene, there is almost no healing agent of liquid phase, while in the capsule formed with 70 wt%-chlorobenzen healing agents are contained. Toluene and xylene are more effective inhibitors than chlorobenzene. The capsule formed with 70 wt%-toluene or xylene contains much more amounts of the healing agent of liquid phase than that formed with 70 %-chlorobenzene, and the coatings with the former capsules have an appreciable self-healing ability.

Self-healing coatings with capsules containing healing agents have been developed for the corrosion protection of metal. In this paper, polyurethane capsules were synthesized under different conditions to examine the size and shape of capsules, and selfhealing ability of coatings with capsules dispersed was examined after damaging the coated layer by scratching with a cutter blade. The size and shape of capsules depended on the concentration of chlorobenzene in cyclohexanone used as a solvent of prepolymer solution. The capsule formed with 70 % of chlorobenzene gave a self-healing capability to the coated layer by releasing the healing agent after damaging. The amount of glycerol added for the formation of the polyurethane capsule shell affected the self-healing ability of the coated layer. The coating with the capsule formed with small amounts of glycerol showed a high healing ability, while, with large amounts of glycerol, the selfhealing ability was relatively low.