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Mechanism of vinyl acetate emulsion polymerization

1958; Wiley; Volume: 32; Issue: 125 Linguagem: Inglês

10.1002/pol.1958.1203212509

1542-6238

David M. French,

Pickering emulsions and particle stabilization

Abstract The emulsion polymerization of vinyl acetate was investigated with the use of block copolymers of ethylene and propylene oxides (commercially known as Pluronic surfactants) as emulsifying agents. By electron microscopy, the average polymer particle size was determined as a function of conversion of monomer to polymer and as a function of the surfactant concentration. It was found that the number of polymer particles remained constant during the reaction. The polymer surface area per unit volume of completely polymerized emulsion was proportional to the surfactant concentration. In contrast with styrene polymerization, the number of particles varied with the cube of the emulsifier concentration, and the number of particles per unit of surfactant was much less than the number that would have been expected with styrene. It was concluded that the results were consistent with polymerization theory. An expression giving the number of polymer particles produced in the reactions proved to be much simpler than the accepted equation used in the case of water insoluble monomers such as styrene. This simplicity arises from the partial water solubility of vinyl acetate, which enables the monomer to diffuse completely into the polymer particles very early in the reaction. The variation of latex viscosity with polymer particle size was also investigated. At constant solids concentration, the logarithm of the viscosity was proportional to the polymer surface area per unit of latex.