Synthesis and characterization of sulfonated polyol-based waterborne polyurethane-polyacrylate hybrid emulsions

Polyurethane (PU) dispersion was prepared with sulfonate groups to make the PU dispersible. Then, polyurethane-polyacrylate (PU-PA) hybrid emulsions were synthesized by seeded emulsifier-free emulsion polymerization with the previously synthesized PU dispersion as a source of seed particles. In the results of the particle-size distribution of the PU-PA hybrid emulsions, the average particle size of the hybrid emulsions increased from 1.2 to 9.1 μm when the polyacrylate content was increased from 0.2 to 1.0 by weight. In addition, the scanning electron microscopy results showed that the size of the polyacrylate latex particles was increased with increases in polyacrylate content. This result suggests that the hydrophobic polyacrylate can easily diffuse into PU particles, where the free radical chain-growth polymerization takes place. In the thermal analysis results, shifts in T_g,1 and T_g,2 were observed, which are related to the partial compatibility and inter-diffusion of the PU dispersion and PA components. The TGA curves shifted to a higher temperature with increases in polyacrylate content, which indicates a higher thermal stability of the PU-PA hybrid emulsion films. The PU-PA hybrid emulsion films showed improvement in the thermal stability and mechanical properties when compared with the pure polyurethane film, due to the increase in the formation of strong interaction between the PU and PA molecules.