Rheokinetics and the influence of shear rate on the Trommsdorff (gel) effect during free radical polymerization

Some rheokinetic studies of free radical polymerization have been published in the past. They generally make modeling of the time dependent increase o f viscosity possible at low degrees of conversion, where Newtonian behavior holds and the rheokinetic equations can be linearized. In this paper we tr y to extend the rheokinetic approach to the region of high degrees of conve rsion, where the reacting solution is non-Newtonian and the shear rate at w hich the polymerization is performed becomes a fundamental parameter. Moreo ver, nonlinear phenomena such as the Trommsdorff effect and phase separatio ns are likely to occur. The principal result of this study is that the Trom msdorff effect is reduced and sometimes eliminated when the polymerization is performed at high shear rate. Instabilities of the time dependent increa se of viscosity occurred when the conversion was higher than 85%. They were attributed to phase separation of the macromolecules under shear flow.