The rate of emulsion polymerization of vinylidene chloride has been measured as a function of catalyst and surfactant concentration in the system consisting of vinylidene chloride, water, ammonium persulfate, sodium metabisulfite, and sodium lauryl sulfate. The polymerization may be divided into three rather well-demarcated stages. In the first, a normal emulsion polymerization occurs at a rate which depends on the 0.6-power of the catalyst concentration and the 0.6-power of the surfactant concentration. In the second stage, the rate drops to less than half that of Stage I. The percentage conversion at which Stage II begins increases with increasing surfactant concentration. Stage II is absent at very high surfactant concentrations (10 g./100 g. monomer). In the third stage, the rate increases and may exceed the rate of Stage I; it depends on the first power of the catalyst concentration and is independent of surfactant concentration. Addition of catalyst at the end of the first stage does not affect the rate of Stage II but increases the rate of Stage III. These results are discussed in relation to the theories of Harkins, Smith, and Ewart.
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