KINETICS AND MECHANISMS OF UNSEEDED EMULSION POLYMERIZATION OF METHYL-METHACRYLATE

Unseeded emulsion polymerization of methyl methacrylate was carried ou t at 50-degrees-C using sodium lauryl sulfate as emulsifier and potass ium persulfate as initiator, respectively, to clarify the effects of e mulsifier, initiator and monomer concentrations initially charged on t he kinetic features of the polymerization such as the number of polyme r particles produced and the course of polymerization. To describe the observed kinetic features, a quantitative kinetic model for particle nucleation and growth is proposed on the basis of the assumption that polymer particles are generated from emulsifier micelles. Furthermore, the rate coefficients for radical termination and propagation in the polymer particles are empirically correlated as a function of the weig ht fraction of polymer in the polymer particles. It is shown that by u sing these empirical rate coefficients and the proposed kinetic model, the observed monomer conversion versus time histories can be successf ully simulated up to almost the end of polymerization, when the emulsi fier concentration is higher than the critical micelle concentration.