Abstract:

The surface of nano-silica sol was modified by vinyl triethoxy silane, in which the vinyl groups were grafted onto the surface. Then the nano silica sol modified polysiloxane miniemulsion was synthesized by in-situ emulsion polymerization by reaction of it with vinyl silicone monomer and acrylate monomer using potassium persulfate as initiator. The influence of polymerization temperature and emulsifier on the emulsion polymerization stabilities, water absorption rate of latex film and the particle size of the latex were studied systematically. The results indicated that the conversion rate was the highest when the emulsion polymerization temperature was controled respectively at 80 ℃,90 ℃, when the emulsifer of AEO and LAS were  used with a mass ratio of 1.5: 1~2: 1 and the emulsifier content used in the range of 1. 5%-2.0%. The emulsion polymerization stability was the best and the water absorption rate was as low as 3. 0% then. The TEM results showed that the structure of latex particles were nano-SiO₂ as the core, silicone polymer as shell. And the number of free SiO₂ particles in nano composite latex was much less than that in the blend of polysiloxane emulsion and silica sol.

Key words: polysiloxane, nano-silica sol, in-situ emulsion polymerization, vinyl triethory silane

摘要： 采用乙烯基三乙氧基硅烷对纳米硅溶胶进行表面改性，使其表面接枝上可反应的乙烯基官能团，以过硫酸钾作为引发剂，与乙烯基有机硅单体、丙烯酸酯类单体进行原位聚合反应制备纳米硅溶胶改性聚硅氧烷微乳液。 系统研究了聚合温度、乳化剂对聚合反应过程中乳液稳定性、乳胶膜吸水率以及乳胶粒子粒径的影响，结果表明:聚合过程中反应温度分别控制在 80 °C 、90 °C ，转化率最高; 烷基聚氧乙烯醚(AEO)与十二烷基苯磺酸钠(LAS)质量比为 1.5∶1~2∶1，乳化剂用量为 1.5%~2.0% 时，制备的乳液稳定性最好，乳胶膜的吸水率低于 3%，与其他共混乳液、聚硅氧烷乳液相比，吸水率显著降低;透射电子显微镜(TEM)观察结果显示:乳液中存在以纳米 SiO₂ 为核、聚硅氧烷聚合物为壳的结构形态，与共混乳液相比，改性乳液中游离的纳米 SiO₂ 粒子数大大减少。

关键词: 聚硅氧烷, 纳米硅溶胶, 原位聚合法, 乙烯基三乙氧基硅烷