St-g-AM反相乳液法接枝共聚反应的动力学模型

研究采用反相乳液方法进行淀粉与丙烯酰胺接枝共聚反应的机理,推导并修正淀粉与丙烯酰胺反相乳液法接枝共聚反应动力学模型,考察了引发剂浓度I]、乳化剂浓度E]、单体浓度M]和淀粉浓度St]等因素对表观聚合速率的影响,验证反应动力学模型。结果表明,本实验得出的动力学关系式为:Rp∝I]0.93M]1.28St]1.47E]0.61,与理论推导出的动力学方程Rp∝I]0.5～1M]1～1.5St]0.5～1.47E]0.6基本一致,说明淀粉与丙烯酰胺在反相乳液中进行接枝共聚反应符合自由基聚合机理,引发过程由引发剂受热分解生成初始自由基和初始自由基攻击淀粉分子形成淀粉骨架自由基两部分构成;在聚合过程中,单基终止和双基终止反应同时存在。

Kinetics Model of Graft Copolymerization of Acrylamide onto Starch in Inverse Emulsion System

The kinetics model of graft copolymerization of acrylamide (AM) onto starch in system of inverse emulsion was educed and modified to fit the real experimental results,and validated by experiment,with ammonium persulfate as the initiator,the graft copolymerization reactive mechanism was investigated and the influences of the concentration of initiator,monomer,starch,and emulsifier on polymerization rate were described.The results show that dependence of the polymerization rate,Rp,on the concentrations of four components in the polymerization system can be expressed by the following equation:Rp=KpI]0.93M]1.28St]1.47E]0.61,which is almost accordant with the kinetic equation from theoretical results,Rp=KpI]0.5～1M]1～1.5St]0.5～1.47E]0.6.It is concluded that the graft copolymerization reaction of hydrophilic monomer onto starch in inverse emulsion accords with the mechanism of free radical polymerization,and the unimolecular and bimolecular terminations of free radicals are concomitant presence in the reaction process.