Improving self-healing performance of polyurethane coatings using PU microcapsules containing bulky-IPDI-BA and nano-clay

In this study, polyurethane-based microcapsules filled with bulky isophorone diisocyanate, IPDI, were prepared via interfacial polymerization method in an oil-in-water emulsion. For this purpose, at first, 2,4-toluene diisocyanate, TDI, based pre-polymer was synthesized and used for the preparation of microcapsules shell compound. n-Butyl acetate solvent was used in the synthesis of both pre-polymer and microcapsules as a low toxic solvent. Various techniques and methods were used to characterized pre-polymer and microcapsules. Mechanical properties of microcapsule-embedded polyurethane, PU, coating was studied using tensile strength measurement under three different conditions (intact, scratched and healed). The standard salt spray test method was used to analyze the healing ability of microcapsules within the PU coatings. The crack healing properties of the PU coatings was defined using SEM micrographs. The results showed increasing healing efficiency by increasing microcapsule content. The best healing and corrosion performance was achieved for the coating with 1 wt % nanoclay and 5 or 10 wt % microcapsules as a result of barrier properties of intercalated and/or exfoliated clay platelets within the coating formulation.