Synthesis and characterization of siloxane-modified two-component waterborne polyurethane

A series of siloxane-modified two-component waterborne polyurethane (2K WPU) was synthesized by the reaction between siloxane-modified hydroxyl-functional polyurethane aqueous dispersion and the hydrophilic-modified polyisocyanate. The siloxane-modified 2K WPUs were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and surface contact angle measurement. The effect of DHPDMS content on the application properties (water and chemical resistance, flexibility, impact resistance, dry time, gloss, hardness and adhesion) of siloxane-modified 2K WPU coatings was also investigated. The results showed that the siloxane-modified 2K WPUs had better thermal stability owing to the forming of SiOSi crosslinking network and good surface properties due to the enrichment of siloxane chains on the surface of films compared with conventional 2K WPU. The application properties of the siloxane-modified 2K WPUs are satisfactory for their use in coatings.