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Mechanism of emulsion polymerization of vinylidene chloride. II. Effect of coalescence of polymer particles on kinetics

1961; Wiley; Volume: 5; Issue: 13 Linguagem: Inglês

10.1002/app.1961.070051305

1097-4628

John C. Light, Leon Marker, Anthony T. Santonicola, Orville J. Sweeting,

Surfactants and Colloidal Systems

In seeking an explanation for the unusual kinetics observed in the persulfate-catalyzed emulsion polymerization of vinylidene chloride, the role of particle coalescence has been examined. A theory has been proposed and the predicted results have been compared with experiment. Development of the theory assumes that after excess surfactant (sodium lauryl sulfate) has been removed from the solution by adsorption on the surface of growing polymer particles, coalescence commences as a second-order process with an invariant specific rate constant, and that the rate of polymerization per particle increases linearly with particle volume (it is assumed that more than one growing chain can exist in a particle). The equations derived involve two adjustable parameters: B, a measure of the coalescence rate which is fixed from best fit of one experimental resin, and A, a function of the catalyst concentration. The equations predict a minumum in the conversion rate at some time after the coalescence starts. Data for the third stage of the per-sulfact-catalyzed polymerization of vinylidene cholride can be explained by this theory. It is shown that particle coalescence alone cannot completely explain all of the observations which have been made on this system, however; in particular, the extent of slowdown in Stage II greatly exceeds that predicted by theory.