Preparation Of Functional Coating By Siloxane Sol-Gel Method

With the continuous developments of nano technologies, the demands to new functional materials has become larger and lager. New composite functional coats combining nano materials and surface coating technique has definitely expanded the application field of nano materials, thus become a main developing direction in nano materials research all over the world. Presently, many methods had been developed successfully to prepare nano coat on solid substrates. However, simple and economical processes to mass-produce nano-coating still remain to be found.In this paper, the oxysilane monomer, e.g., KH570(3-methacryloxy-propyl-trimethoxysilane) was hydrolyzed, polymerized in alcohol/water mixture at optimized pH value (-4.0) and then coated on glass substrate by dip coating technique. This process factually was a sol-gel procedure. The influence of hydrolyzation, polycondensation and curing conditions on the coat properties were investigated systematically. The results showed that when the KH570was hydrolyzed in95%alcohol for1h at room temperature and then coated on galss surface following drying at120℃for3h, thin coat with hardness5H and adhesion strength up to0class was created. This coat also showed good aging resistance performance. The mechanism of coat formation, e.g., polycondensation and curing of hydrolyzed oxysilane, was studied by analyzing FTIR spectra of coat before and after solidification. The coat prepared by such simple and economical method can be used as a matrix for further filling functional nanoparticles.Afterwards, TiO2photo induced superhydrophilic surfaces were prepared by mixing above oxysilane sol and commercial nano TiO2sol and then coat them on glass and PC substrates following drying at120℃for3h. The influence of solid content of TiO2sol on the coat wettability responses to light irradiation and the coat transparency were investigated. The surface structure of the coat was observed by SEM. The results showed that when the content of TiO2was0.24%, the comprehensive properties of the coat approached the best, e.g., the visible light transmissivity was more than90%and the surface static water contact angle decreased to0°after10min UV irradiation. This study would be helpful in manufacturing TiO2photo induced superhydrophilic surface cost-effectively and in a large scale.Similarly, transparent and heat insulating coats based on atimony doped tin oxide (ATO) nanoparticles were also prepared by mixing commercial ATO nanoparticle/alcohol suspensions with above oxysilicane sol and then coating them on glass, polycarbonate and polyethylene terephthalate (PET) substrates. Effect of the solid content of ATO nanoparticles on the heat-insulating effect and on the coat responses to solar light were investigated. The surface structure was observed by SEM.The results showed that when the content of ATO in composite sol was10%, the comprehensive properties of the coat were the best. The coats’heat-insulating effect were measured by long time tracking the temperature changes in polystyrene foam boxes covered by ATO coated glass plate, PC plate and PET plate. The temperatures in ATO glass covered box were always lower than those in general glass covered box (～13℃). The visible light transmittance was up to85%and the infrared radiation insulation was over70%. While to ATO-PC plate, these data were10℃,80%and70%, respectively. While to ATO-PET plate, these data were10℃,60%and80%, respectively Compared with traditional polyurethene matrix, polyoxysilane matrix prepared here remarkably improved the coat hardness and resistances to aging and water immersing.