苯乙烯热引发本体聚合的动力学研究 1 转化率与时间的关系

基于三段聚合模型 (TSPM) ,研究了 10 0— 2 0 0℃苯乙烯 (St)热引发本体聚合。结果表明 ,TSPM同样适用于描述 St热引发本体聚合。用文献中发表的大量实验数据进行 TSPM标绘表明 ,由低转化阶段向凝胶效应阶段转变时的临界转化率 x1与聚合温度无关 ,为一定值 ,大致等于 0 .5。同时 ,聚合各阶段的表观速率常数可用阿累尼乌斯 (Arrhenius)方程关联。用得到的表观速率常数计算方程和 x1,对转化率与时间关系进行了计算 ,并与文献中发表的大量实验数据作了比较。结果表明 ,二者较为吻合

A STUDY ON KINETICS OF BULK THERMAL POLYMERIZATION OF STYRENE

In this paper, the expressions for calculating number average molecular weight were derived based on Three Stage Polymerization Model (TSPM) and the second order initiation mechanism for bulk thermal polymerization of styrene (St). With the use of the experimental data of the molecular weight in literatures, the general expressions for calculating number average molecular weight at different temperature were obtained. It was found from analysis of the expressions that the propagation rate constant k p and chain transfer rate constant to monomer k tr,m or chain transfer constant to monomer C m are unchanged and C m is independent of the reaction temperature from lower conversion to gel effect stage for bulk free radical polymerization. In addition, the obtained results showed that the number average molecular weight is independent of the conversion and only relative to the reaction temperature at lower conversion stage. However, the molecular weights were varied with the conversion at the gel effect stage and the variation was more obvious as the reaction temperature rises.