Synthesis and characterization of UV-curable waterborne Polyurethane–acrylate modified with hydroxyl-terminated polydimethylsiloxane: UV-cured film with excellent water resistance

In this paper, a series of UV-curable waterborne polyurethane–acrylate (WPUA) emulsions were synthesized by using isophorone diisocyanate (IPDI) as the hard segment, polybutylene adipate glycol (PBAG) and different dosages of hydroxyl-terminated polydimethylsiloxane (HTPDMS) as the soft segment, 2,2-dimethylolpropionic acid (DMPA) as hydrophilic chain extender, and pentaerythritol triacrylate (PETA) as the blocking agents. The properties of the WPUA emulsions were then characterized by using Fourier transform infrared spectrometry, Zeta potential analysis, dynamic light scattering, and UV-cured films were characterized through Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, scanning electron microscope, UV–vis spectrophotometer, and thermogravimetric analysis, as well as by measuring the contact angle of water, testing the water absorption. The results indicated that with increasing HTPDMS content in the WPUA, the particle size of the emulsion was increased significantly, while the absolute value of Zeta potential was increased slightly. The resistance of WPUA cured film to water was increased. The ultimate water absorption declined from 11.12 % to 6.81 % and the equilibrium time of water absorption extended from 50 h to more than 100 h. When the HTPDMS content of WPUA was 10.0 wt%, the water contact angle of the cured film was the largest at 114°, which indicated that the surface of the cured film has been changed from a hydrophilic surface to a hydrophobic one. Thermogravimetric analysis results showed that the initial decomposition temperature of WPUA film gradually increased with adding of HTPDMS, performing better thermal stability.