| Acrylic resin is widely used as automotive topcoat owing to its outstanding luster, transparency and weatherability. However, the weatherability of acrylic resin should be further improved, because acrylic resin is easily aging in the short-wave UV light. Nano-TiO2, especial the rutile nano-TiO2, with the better UV shielding could be used to improve the aging resistance property of acrylic resin. In this article, we prepared different crystal phases of nano-crystalline TiO2modified with organic. And then we obtained the nano-TiO2/acrylic dispersions by dispersing nano-TiO2in acrylic resin, and researched the anti-UV properties of nano-TiO2. Our works are listed as follow:(1) Starting from TiO2as Ti sources, rutile nano-TiO2was prepared by Low-temperature liquid phase method. We researched the effection of reaction temperature, recation time, acidity, high-temperature sintering on crystal phase and morphology of products. Temperature effected the crystal phase and morphology of nano-TiO2seriously. Low temperature (<100℃) was benefit for the formation of rutile. And there was a trend of anatase formation from100℃to150℃. But when the temperature rised to a certain extent (highter than180℃), rutile nano-TiO2was obtained. We worked out the best preparation condition, crystallizing4h under80℃. Needle-like nano-rutile was obtaind. and its crystalline could be improved through high-temperature sintering under650℃.(2) Starting from Ti(OBu)4as Ti sources, acetic acid, nitric acid or hydrochloric acid as peptization reagent, sodium chloride or citric acid which were used to control products’ crystal phase, pure anatase, pure rutile and the mixed crystal with different amounts of rutile nano-TiO2including rutile and anatase were prepared by hydrothermal. The effect of citric acid on crystal phase was investigated. The results showed that acetic acid and nitric acid were benefit for the formation of anatase, but hydrochloric acid promoted the formation of rutile. The crucial factor of crystal phase was Cl-but not H+. However, if a little of citric acid was added into hydrochloric acid, citric acid could chelate with Ti(Ⅳ), so the formation of rutile with high crystallinity was hampered. But citric acid will decomposed at190℃with the prolongation of hydrothermal time. So the chelation between citric acid and Ti(Ⅳ) would disappear. That was why the products converted from anatase to rutile. So mixed crystals with different amounts of rutile nano-TiO2including rutile and anatase could be prepared through the changes of reaction conditions, such as, hydrothermal time, the amount of citric acid.(3) The nano-TiO2with different crystal phase, which were synthesised through two different methods in various conditions, were modified with various organic including KH570, oleic acid, oil amine and SDBS. And then we obtained the nano-TiO2/acrylic dispersions through dispersing nano-TiO2in acrylic by ultrasound, and researched the anti-UV properties of nano-TiO2. UV absorption wavelength range of rutile was wider than that of anatase, amorphous and mixed crystals. When the amount of rutile nano-TiO2was0.9%of acrylic resin, it could completely shield all the UV-light with wavelengths below350nm. At the same time, the transmittance was more than63%at550nm in the visible region. UV shielding properties of rutile nano-TiO2prepared by hydrothermal was better than that synthesised by low temperature hydrolysis-sintering, and was far superior to commercial rutile nano-TiO2. |
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