Polydimethylsiloxane-modified, epoxy-resin-based polyol dispersion and its crosslinked films
Waterborne polydimethylsiloxane-modified epoxy-resin-based polyol dispersions were synthesized by the reaction of 2,4-toluene diisocyanate with 2,2-bis(hydroxymethyl) propionic acid, hydroxypropyl-terminated polydimethylsiloxane (HTPDMS), and bisphenol A epoxy resin based polyol. These HTPDMS-modified polyol dispersions exhibited a small particle size and an excellent dispersion stability. Two-component waterborne polyurethane (2K-WPU) was prepared from the HTPDMS-modified polyol dispersion and a hydrophilic-modified polyisocyanate. The structure of the HTPDMS-modified polyol and its crosslinked 2K-WPU films (SEFs) were characterized with Fourier transform infrared and NMR spectroscopies. The effects of the HTPDMS content on the mechanical and thermal properties of the resulting SEFs were investigated. The results show that the thermal stability of the crosslinked SEFs was enhanced with increasing HTPDMS content, whereas the modulus, tensile strength, and pencil hardness values of the films decreased with increasing HTPDMS content. Siloxane segments migrated onto the surface during the film-formation process. The contact angle of the films increased from 71 to 96 °, and the water absorption ratio of the films decreased from 6.6 to 5.0% when the HTPDMS content in the films increased from 0 to 10%. These results indicate that the water resistance of the films was enhanced by the introduction of HTPDMS into the 2K-WPU networks.
J. Appl. Polym. Sci. 2016, 133, 44342.