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 d emonstrate the feasibility of miniemulsion polymerization as a strategy to eliminate the oscillatory behaviour of CSTR reactors, even in very unfavour able conditions. Reactions were carried out under a wide range of operating conditions. No oscillations in the time evolution of the conversion and pa rticle number were observed in any of the miniemulsion polymerizations, whi le the opposite was found in most of the conventional emulsion polymerizati ons. Different dependencies of the emulsifier and initiator concentrations on the reaction rate and particle number were obtained for both emulsion an d miniemulsion polymerizations, as a consequence of the different nucleatio n mechanisms. Further, almost the same average molecular weight was obtaine d for the emulsions and miniemulsions carried out under similar experimenta l conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.