Preparation of Nano - SiO2 Modified Waterborne Polyurethane Coatings and Its Influence on the Anti - Permeability of Concrete

For improving the anti-permeability of waterborne polyurethane coatings to concrete,the silane coupling agent was applied to modify the surface of nano-SiO2 to reduce the reunion degree of nanoparticles,and then the modified nano-SiO2 with better dispersibility was added into the waterborne polyurethane coatings.The modification effect of silane coupling agent on nano-SiO2 was analyzed by thermal analysis (TG),infrared spectroscopy (FT-IR) and dynamic light scattering (DLS),and the effect of nano-SiO2 on the morphology and composition of waterborne polyurethane coatings was also expounded.Furthermore,the influence of nano-SiO2 modified waterborne polyurethane coatings on the anti-permeability of concrete was analyzed.Results showed that the nano-SiO2 modified by silane coupling agent possessed less-OH on the surface and a lower reunion degree.Comparing with the concrete specimens painted with the polyurethane coatings containing no SiO2 or unmodified nano-SiO2,the concrete specimen painted with polyurethane c