A method for synthesis of waterborne polyurethane using an eco-friendly surfactant

In general, waterborne polyurethane molecular chains containing hydrophilic groups usually require extended drying times to achieve sufficient film formation, thereby increasing energy consumption. The preparation of high-solid content waterborne polyurethane has attracted significant attention in both scientific research and industrial applications. The primary challenges associated with increasing the solid content of waterborne polyurethane are poor fluidity and inadequate storage stability. In this study, two surfactants, sodium lauryl sulfate and polyethylene glycol, were incorporated into the emulsification process of waterborne polyurethane to achieve a solid content of more than 50 %. The effect of different addition levels ranging from 1 to 5 wt% on viscosity, storage stability, physical and mechanical properties, thermal properties, and surface morphology of dried WPU films was further investigated. Waterborne polyurethane dispersion without surfactants solidified within a month, whereas those with surfactants remained stable for up to four months. Furthermore, the addition of sodium lauryl sulfate and polyethylene glycol significantly reduced the viscosity of waterborne polyurethane to 6-80 P and 3-17 P, respectively. Compared to SDS, PEG offers several advantages, including non-toxicity, biocompatibility, and solubility in various solvents. The addition of 1 wt% polyethylene glycol resulted in a stable waterborne polyurethane dispersion, achieving a solids content above 50 % with a viscosity of 17 P. This fundamental study establishes a pathway for preparing high solid content WPU using environmentally friendly surfactants.