氧化还原引发体系的宏观动力学研究

Kinetics study of a redox initiator system

采用氧化还原引发体系——异丙苯过氧化氢/硫酸亚铁/乙二胺四乙酸钠盐/甲醛合次硫酸氢钠(CHP/FES/EDTA/SFS),引发丙烯酸丁酯种子乳液聚合。系统考察了该引发体系的引发机理及其组分的配比及用量等因素对聚合反应动力学的影响。研究表明,聚合反应速率和单体的总体转化率皆随CHP或SFS的用量增加而增加;CHP/SFS的最佳物质的量比为1.10/3.81,并非传统认知的等物质的量比;另外,EDTA/FES的最佳物质的量比为(2.19×10-5)/(7.12×10-6)。聚合反应速率随着Fe2+用量的增加先增加后降低。随着反应的进行,体系的pH值降低。并针对发现的极限转化率现象(转化率≤20%),从实际络合常数和反应速率的角度进行了解释。

Seeded emulsion polymerization of n-butyl acrylate was initiated by a redox initiator system:cumene hydroperoxide/ferrous sulfate hexahydrate/ethylene-diaminetetraacetic acid monosodium salt/sodium formaldehyde sulfoxylate(CHP-Fe2+-EDTA-SFS).Effects of components content and the mechanism in the redox system had been studied systemically.The polymerization rate and the overall conversion increased with increasing CHP and SFS concentration.Interestingly,the optimal molar ratio of CHP/SFS was 1.10/3.81 rather than being equimolar.In addition,an optimal molar ratio of EDTA to ferrous ions(2.19×10-5 mol/7.12×10-6 mol)was found.The polymerization rate increased first and then decreased with increases in ferrous ion concentration.The pH value decreased as the polymerization proceeded.A limiting conversion phenomenon of conversion not being able to exceed 20%was found,and an explanation was proposed on the basis of the views of the practical cumulative formation constant and reaction rate.