The Sol-Gel Transition Of Waterborne Polyurethane Dispersion And Its Preparation Based On Thiol-Isocyanate Click Chemistry

The waterborne polyurethane(WPU)dispersion containing less or no solvent is a kind of environment friendly dispersion,owing to water in place of organic solvent as a dispersion medium.Meanwhile,there are advantages in operation,transportation and using.But its disadvantages such as low stability,poor water resistance,and low solid content,limit its further application.To explore the stability of WPU dispersions,the temperature and mechanism of sol-gel transition for WPU dispersion using ethylene diamine as a post-chain extender were investigated.To improve the stability and solid content of WPU dispersions,the thiol-diisocyanate click reaction was applied to the post-chain extension,and showed that it has high efficiency and rapid rate under facile conditions.This WPU dispersion had good stability and high solid content.The impacts of NCO/OH ratio on the stability of dispersions,the water resistance and mechanical properties of films were studied.In order to improve the water resistance of WPU,the introduction of hydroxyl-terminated polybutadiene(HTPB)partly replaced the polyether glycol,and the hydroxyl-terminated HTPB waterborne polyurethane dispersions(WPUHS)were successfully synthesized.Then WPUHS was modified with cross-linking of thiol-ene click chemistry under UV irradiation condition.The effects of HTPB content on the stability of dispersions,the water resistance and mechanical properties of WPUHS films were studied.And the influences of photoinitiator and illumination time on the mechanical properties of polyurethane films were investigated.