Continuous Emulsion Polymerization

Abstract

Abstract The theories presented can be used for prediction of particle size, particle formation, rate of polymerization, and molecular weight for the emulsion polymerization of styrene in continuous stirred-tank reactors. The incorporation of Stockmayer's modification of the Smith-Ewart theory into Gershberg's continuous reactor model has helped to account for the formation of fewer but larger particles when the reactor is operated at long mean residence times. The use of a different particle generation relation by Nomura and coworkers has led to better agreement between theory and experiment for particle number and polymerization rate at low values of mean, residence time. Their model also fits transient data better than Gershberg's. However, the prediction that free-radical movement into particles is independent of particle size is not very satisfactory. Perhaps the better agreement between theory and experiment results because of the introduction of an additional experimentally determined parameter. Data for other monomers do not follow theoretical predictions as closely as styrene. For methyl acrylate the particle number data are in reasonable agreement with theory but the polymerization rate data show completely different trends. An improved, more general, theory will undoubtedly require a more complete understanding of particle formation and particle growth mechanisms. Particle size distribution measurements would be a valuable asset in developing improved competitive particle growth models.