Emulsion polymerization of styrene using reaction calorimeter. II. Importance of maximum in rate of polymerization

The importance of the maximum in the heat of reaction or rate of polymeriza tion curve (R-p max) is defined by describing the main processes that occur around this maximum. The relevance of knowing when it occurs is illustrate d by experiments performed in an automated reaction calorimeter. The effect of adding additional emulsifier or monomer after R-p max on the evolution of the number of particles and heat of reaction was studied. No new particl es were formed once the maximum in the rate of polymerization was reached, whether either monomer or emulsifier was added after this maximum. Therefor e, by knowing the conversion or time when the maximum in the rate-or polyme rization appears, it was possible to either improve the particle stability or increase the particle size and latex solids content, without increasing the final number of particles and without significantly affecting the react ion kinetics. This can be an important application of calorimetry. The resu lts showed that R-p max defines several important factors in the emulsion p olymerization process: the end of nucleation and the disappearance monomer droplets. (C) 1999 John Wiley & Sons, Inc.