Synthesis And Properties Of UV-curable Waterborne Polyurethane/Inorganics Composites And Morphology Of Their Films

UV-curable waterborne polyurethane is a kind of environmentally friendly material which has important significance in the development of coating industry, the protection of environment and the saving of energy. For this reason, waterborne polyurethane (WPU) has received much attention. In this study, we use crosslinking modification and doping modification to improve the water resistance and mechanical property of WPU materials.We synthesize the UV-curable polyether-based WPU by introducing the C=C double bonds into molecular chains. The KH-570modifying silica was used to modify the UV-curable polyether-based WPU. Because of the existence of organic molecule chains from the functionalized silica, the compatibility of WPU with silica was improved obviously. This makes the composite latex possesses certain stability when the silica content rose up to10wt%. The functionalized silica was combined with WPU by chemical bonds and existed as effective cross-link points to form composites after irradiated by ultraviolet. The existence of functionalized silica improved thermo-stability, hardness, water resistance and solvent resistance of composite films effectively and the composite films possessed good transparency.Because of the good hydrophobicity of polyester, we prepared the polyester-based waterborne polyurethane to promote the hydrolytic resistance of this kind of WPU. In this study, the polyester-based WPU was modified by the functionalized silica. The composite film possesses excellent transparency when the silica content rose up to17.5wt%. The thermo-stability and hardness of composite films improved effectively because of the doping of functionalized silica. Otherwise, the water resistances of the films were improved effectively.The fly ash (FA) is a kind of inorganic particle (micrometer) which is feasible for WPU modifying. Firstly, the FA particles were modified by the KH-550. And then, the product reacted with the isophorone diisocyanate (IPDI). The WPU/FA composites were prepared by in-situ polymerization. The test results show that the doping of FA-NCO make the water resistance and the solvent resistance apparent improvement.On the base of all above mentioned the inorganic particles were combined with WPU by chemical bonds and existed as effective cross-link points to form composites. Because of the existence of organic molecule chains on the surface of functionalized inorganic particles, the compatibility of inorganic with WPU were improved obviously. In short, crosslinking and doping modification is an effective method to improve the properties of WPU.