UV-curable cationic waterborne polyurethane from CO2-polyol with excellent water resistance

Abstract Though cationic waterborne polyurethane (CWPU) has been regarded as an important environmental friendly material, it is hampered by poor water resistance due to incorporation of excessive hydrophilic groups to assure the stability of water dispersion. Here UV-curing in combination with terminal hydrophilicity induced dispersion strategy was employed to prepare water-resistant CWPU from CO2-polyol which was an oligoethercarbonate diol from telomerization of propylene oxide and CO2. In this system, multiple vinyl ether side chains were incorporated on CWPU backbone using 3-allyloxy-1,2-propanediol as functional chain extender to achieve efficient UV curing, and a small amount of terminal hydrophilicity was designed to ensure the stable dispersion of CWPU. The typical UV-cured CWPU film reached water absorption equilibrium at 72 h, maintaining water absorption rate as low as Ca. 5.8% even immersed in water for 240 h. Moreover, compared with traditional polyester and polyether polyols from petroleum resources, UV-cured CWPU from CO2-polyol not only used partially sustainable raw material like CO2, but also provided excellent water resistance in corrosive media for a long time (tensile strength retention above 90% for 336 h) due to hydrolysis resistant structure like carbonate and ether units in CO2-polyol.