丙烯酰胺/氧化-还原引发体系的反相乳液聚合

Inverse emulsion polymerization of acrylamide with redox initiator

采用煤油为油相 ,Span80和Op10为复配乳化剂 ,以K2 S2 O8 Na2 SO3 氧化 还原体系为引发剂 ,研究了丙烯酰胺的反相乳液聚合。通过考察引发剂浓度、单体浓度、乳化剂用量、反应温度对反应速率及分子量的影响 ,确定了动力学表达式 :Rmax∝ [I]0 68[M]1 2 90 [E]0 71,Mη∝ [I]-3 66[M ]0 640 [E]-0 77;聚合表观活化能Ea=4 1 11kJ/mol。反应速率 时间曲线上未出现恒速平台 ,聚合过程不存在恒速期 ;扫描电镜未观察到反应后乳胶粒径比反应前乳胶粒径有数量级的下降 ;搅拌速率较低时 ,聚合反应的转化率—时间曲线常呈不规则形状 ,结果不易重复且乳胶粒径较大 。

The inverse emulsion polymerization of acrylamide in kerosene was studied with a blend of two surfactants (Span80 and Op10) as emulsifier and K 2S 2O 8 Na 2SO 3 as initiator. The influences of the initiator concentration, amounts of monomer and emulsifier, as well as the reaction temperature on the polymerization kinetics were investigated and the kinetic expressions obtained as follows R max ∝ 0 68 1.29 0 0 71 ; M η∝ -3 66 0 64 0 -0 77 . The overall activation energy of polymerization for redox initiator is 41 11?kJ/mol. The reaction rate time curve shows that no stage of constant reaction rate exists in this polymerization system; with the scanning electron microscope, the initial emulsions and the final latexes are found following the same level of particle sizes; in lower stirring rate, the shape of conversion time curve becomes irregular and results can not be reproduced properly, the size of latexes is larger than that in higher stirring rate; all the above results lead to the conclusion of monomer droplet nucleation mechanism in the polymerization system.