UV-curable hybrids of hyperbranched and linear polyurethane dispersions

A series of UV-curable hybrids of hyperbranched and linear polyurethane dispersions (HLPUDs) were synthesized by a three-step process. Hybrids of HLPUDs were obtained by mixing acrylated hyperbranched polyurethane (HBPUA) with linear acrylated polyurethanes (LPUAs) and then being dispersed with water. The high density of acrylic groups on the surface of the HBPUA is very useful for the post UV curing. The synthesis of HBPUA and the effects of the HBPUA loading on the particle size (PS) of the HLPUDs as well as the thermal and the mechanical properties of the resulting cured films were characterized by Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering particle analysis, differential scanning calorimetry (DSC), dynamic mechanical analysis, thermal gravimetric analysis, and tensile measurements. The PS of the hybrids of HLPUDs were found to increase slightly from 38 to 76 nm with increase of the HBP content. Compared with the pure LPUA, the mechanical properties of the hybrids were enhanced dramatically, which could be correlated to the microstructure of the hybrids.