UV-curable coating crosslinked by a novel hyperbranched polyurethane acrylate with excellent mechanical properties and hardness

A novel hyperbranched polyurethane acrylate (HBPUA), successfully synthesized based on a reaction of hyperbranched polyether (HBP-OH) with toluene diisocyanate (TDI) and hydroxy-ethyl acrylate (HEA), was incorporated into photosensitive polyurethane acrylate (PUA) as crosslinker to prepare a series of high-performance UV-curable coatings. The structure of HBPUA was characterized by Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance (H-1 NMR). The kinetics of the curing process was monitored using real-time IR. The results indicated that the final double bond conversion was associated with acrylate double bond concentration and the initial viscosity of the curing system. The properties of cured films were investigated by tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The hardness, abrasion resistance, adhesion on plastics and transparency of the cured coatings were also tested. The results revealed that tensile strength and storage modulus of the cured film could be improved by 148% and 74%, respectively, by adding HBPUA, and that the hardness of the cured coating could reach 9H. Furthermore, the cured coatings also showed excellent adhesion on PC and PVC sheets, enhanced abrasion resistance and thermal properties as well as outstanding transparency.