Preparation And Modified Of Nano-silica

Nano-silica is a kind of inorganic non-metallic material and was widely used in various fields. But its size was small, contains a lot of silicon hydroxyl on surface with high surface energy, which maked it keep in a unsteady state of thermodynamics, and leaded to agglomerate to affect its application performance. Its high chemical reactivity was conducive to chemical modification by other materials to improve the surface performance and maked it get better application in the organic material. This paper first used different types of surfactants to modify nano-silica and comed to the conclusion that hexadecyl trimethyl ammonium bromide(CTMAB) was the modified optimum surfactant. Furthermore, it explored the influence of CTMAB amount, reaction temperature, reaction time and stirring speed on the result of modification. The best conditions confirmed by the orthogonal experiment optimization method was the following ones: surfactant amount 4%, reaction temperature 55 ℃, reaction time 60 min and stirring speed 375 r/min. After modified, dibutyl phthalate(DBP) absorption number of nano-silica increased from 2.47 m L/g to 2.76 m L/g, and hydrophobic rate increased from 11.62% to 19.80%. Due to the limitation of the simple usaged of surfactant, this paper used different silane coupling agent collaborative modified nano silica to confirm that hexadecyl trimethoxy silane(CG1631) was the modified optimum silane coupling agent. It used conductivity method to monitored CG1631 hydrolysis condition on-line, and discussed the influence of hydrolysis way, hydrolysis solvents, hydrolysis solvent pH, hydrolysis solvents alcohol water volume ratio, hydrolysis reaction temperature on the hydrolysis degree. The best hydrolysis conditions were determined as follows: hydrolysis way was positive hydrolysis, hydrolysis solvent was ethanol and water, hydrolysis solvent pH was 4, hydrolysis solvents alcohol water volume ratio was 1:1, hydrolysis reaction temperature was 25 ℃. In the process of preparation of nano silica with the hydrolysis CG1631 as collaborative modifier, it also studied the influence of silane coupling agent amount, reaction temperature, reaction time, and adding time on the modification effect. The best modification condition confirmed by the response surface method was: CG1631 amount 9.31%, reaction temperature 93.28 ℃, reaction time 2.18 h, adding time 20 min. Under the collaborative modified condition, DBP absorption number of nano-silica reached 3.85 m L/g. In this paper, composite film was prepared by adding the synergy of the modified nano-silica to the polyacrylate emulsion. The results showed that modified nano-silica could enhance anti-ultraviolet performance of polyacrylate film, which maded ultraviolet absorbing capacity increased at 240 nm-350 nm wavelength and absorbance at the maximum absorption wavelength at 276 nm increased from 0.47 to 3.86, and significantly enhanced the dispersibility of nano-silica in the organic matrix.