醇溶剂和酸催化对TEOS/KH560溶胶凝胶的影响

Influences of Alcohol Solvents and Acid Catalysts on Sol-Gel Process of Tetraethylorthosilicate/KH560 Silane and Performance of Resultant Hybrid Silica Sol

过去,对硅溶胶制备的研究仅限于对单溶剂的定性探讨。应用溶胶凝胶法制备了稳定的正硅酸四乙酯(TEOS)/γ-(2,3-环氧丙氧)丙基三甲氧基硅烷(KH560)的杂化硅溶胶。采用在线电导率测试、红外跟踪技术及相关性能测试方法研究了异丙醇、乙醇、甲醇溶剂,盐酸、甲酸、乙酸催化剂对TEOS/KH560水解过程及杂化硅溶胶性能的影响。结果表明,不同溶剂、催化剂对杂化硅溶胶的性能有很大的影响:醇水混合溶剂比单独醇、水溶剂对原料的水解程度更好;随着醇碳链长度的增加,杂化硅溶胶的黏度降低,稳定性及产率提高;以盐酸为催化剂,杂化硅溶胶的存储时间比以甲酸、乙酸催化的短;选择异丙醇∶硅醇摩尔比为1∶13,以甲酸作催化剂,pH值为3.5左右时,杂化硅溶胶的性能最佳。

Tetraethylorthosilicate(denoted as TEOS) and γ-(2,3-epoxypropoxy) propyl-trimethoxyl silane coupling agent(denoted as KH560) were used as the starting materials to prepare stable hybrid silica sol(denoted as TEOS/KH560) via sol- gel process.The effects of alcohol solvents including isopropyl alcohol,ethanol and methanol as well as acid catalysts including hydrochloric acid,formic acid and acetic acid on the hydrolysis process and performances of TEOS/KH560 hybrid silica sol were investigated with on- line conductivity test,infrared tracking technology and related performance test.Results showed that solvents and acid catalysts had great influences on the performance of as-prepared TEOS/KH560 silica sol.As compared with single alcohol or water solvent,the mixed solvents of alcohol- water provided enhanced hydrolysis of the starting materials.With the increase of alcohol carbon chain length,the viscosity of the hybrid silica sol declined,and its stability and yield rose therewith.Moreover,the hybrid silica sol obtained in the presence of HC1 as the catalyst exhibited shorter storage time than those obtained in the presence of formic acid and acetic acid as the catalysts.Particularly,when isopropyl alcohol was used as the solvent and formic acid as the catalyst,while the molar ratio of Si to alcohol was fixed as 1:13 and pH value was fixed around 3.5,as-synthesized TEOS/KH560 hybrid silica sol exhibited the optimal performance.