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Free radical entry in emulsion polymerizations

1992; Wiley; Volume: 53; Issue: 1 Linguagem: Inglês

10.1002/masy.19920530122

0258-0322

Ian Maxwell, Bradley R. Morrison, Robert G. Gilbert, David F. Sangster, Donald H. Napper,

Chemistry and Chemical Engineering

Abstract Measurements of the rate coefficients characterising the entry of free radicals into seed particles in styrene emulsion polymerizations has allowed the rate determining step for entry to be identified. This was found to be the rate of production of oligomeric species in the aqueous phase by monomer addition to the primary free radicals. Once formed the subsequent diffusion of these species to the latex particles (and their incorporation within these particles) is relatively fast, contrary to the assumptions of the previous diffusion controlled theories. The experimental results imply that the entering free radicals contain only two or three monomer units. Thermodynamic considerations show that such species should be both water soluble and surface active. Similar conclusions have been reached for other sparingly water soluble monomers, such as butyl acrylate and butyl methacrylate.