Synthesis and properties of a novel UV-curable waterborne hyperbranched polyurethane

A series of ultraviolet (UV)-curable waterborne hyperbranched polyurethane dispersions (WHPUDs) have been successfully synthesized by modifying the hyperbranched polyester H10, which was prepared using pentaerythritol as a core molecule and dimethylolpropionic acid as monomers, with succinic anhydride, toluene diisocyanate (TDI), and hydroxypropyl acrylate (HPA). The H10 was characterized by H-1 nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry. The properties of the WHPUDs with different content of succinic anhydride and TDI-HPA have been investigated by measuring the stability, the particle size, and the rheological behavior. The effects of the content of succinic anhydride and TDI-HPA were studied in terms of UV-curing rate, water resistance, and thermogravimetric behaviors of WHPUD coatings. The WHPUDs showed good appearance, particle size, viscosity, and storage stability. The WHPUD films showed superior photosensitivity and the percent conversion of C=C bonds reached about 80% when the radiation time was 50 s. Moreover, the UV-cured films had good water resistance and thermostability, which can benefit a waterborne polyurethane resin for waterborne coatings.