乳液聚合导致一种新的转相过程

借助电导率仪、光学显微镜和亚微粒子分析仪等测试手段。研究了乳液聚合导致一种新的转相过程,并用于八甲基环四硅氧烷的聚合中。研究表明:体系以 W/O 相态开始,单体由连续相向水相(分散相)内的胶束中扩散并发生聚合反应,形成 O/W/O 复合乳液。反应过程中连续相体积不断减小,分散相(O/W 复相)体积不断增大,当达到某一临界相比时,体系发生转相,转相后乳液为 O/W。对本实验物系,转相点临界相比主要由初始水油比和乳化剂浓度决定。同常规的乳液聚合相比,伴有转相现象的乳液聚合有其自身的特点,转相使得聚合速率、聚合物粒径及分布、乳液稳定性等发生变化。

THE PHASE INVERSION INDUCED BY EMULSION POLYMERIZATION

The phase inversion induced by emulsion polymerization was studied with the help of conductivity gauge,optical microscopy and BI-90 particle sizer,and was used in polymerization of octamethylcyclotetrasiloxane.The experimental results showed that the system begins with the state W/O.The monomer diffuses across continuons phase into aqueous phase and the polymerization occurs in the micelles of aqueous particle,the system now becomes O/W/O multiple emulsion. During polymerization,the volume of continuous phase decreases while the volume of the dispersion phase(O/W double phase)increases.The ratio of aqueous phase to oil phase varies with polymerization time,and at one critical phase ratio the phase inverstion takes place,and then the system becomes O/W.The phase ratio at phase inverstion point is mainly controlled by the initial ratio of aqueous phase to oil phase and the cocentration of emulsifer.Comparing to the normal emulsion polymerization,the emulsion polymerization with phase inversion has higher polymerization rate,the polymer particle diameter is smaller and particle diameter distribution is narrower,the polymer emulsion has higher stability,especially when the solid content is high.