Comparison between conventional emulsion and miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor

The conventional emulsion and miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor (CSTR) were studied in an attempt to demonstrate the feasibility of miniemulsion polymerization as a strategy to eliminate the oscillatory behaviour of CSTR reactors, even in very unfavourable conditions. Reactions were carried out under a wide range of operating conditions. No oscillations in the time evolution of the conversion and particle number were observed in any of the miniemulsion polymerizations, while the opposite was found in most of the conventional emulsion polymerizations. Different dependencies of the emulsifier and initiator concentrations on the reaction rate and particle number were obtained for both emulsion and miniemulsion polymerizations, as a consequence of the different nucleation mechanisms. Further, almost the same average molecular weight was obtained for the emulsions and miniemulsions carried out under similar experimental conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.