Chemically and thermally stable isocyanate microcapsules having good self-healing and self-lubricating performances

Abstract

A new approach was developed to load 4,4′-bis-methylene cyclohexane diisocyanate in microcapsules, with outstanding stability in thermal and chemical environments, and excellent efficiency for both self-healing and self-lubricating uses. Well-dispersed microcapsules with diameter of 80 ± 22 µm and shell thickness of 3.8 ± 0.2 µm were produced with a core fraction of 74 ± 1.3 wt% as determined by titration. In thermal environments, the microcapsules started to lose 5% mass at 230 °C, which was higher than the boiling point of pure HMDI and thermal decomposition temperature of shell material. In chemical environments (hexane, xylene, ethyl acetate and water), the impermeable microcapsules reserved more than 90% of original core material after 20 days immersion. More interestingly, final microcapsules survived successfully in acetone losing only 25% of core material after 24 h. Parameters including microcapsules size, concentrations, immersion durations and solvent polarity were investigated systematically to obtain the stability of microcapsules in organic solvents. The smart coatings (10 wt% microcapsules) showed outstanding self-healing anticorrosion efficiency in sodium chloride solutions, and their friction coefficient decreased by 80% than control samples.