Microemulsion polymerization of styrene using developed redox initiation system and study of rheological properties of obtained latices

Microemulsion polymerization of styrene was kinetically studied using a pot assium persulfate (KPS)/P-methyl benzaldehyde sodium bisulfite (MeBSBS) add uct as the developed redox pair initiation system. The rate of microemulsio n polymerization of styrene was found to be dependent on the initiator, emu lsifier, and monomer to the powers of 1.4, -0.77, and 0.83, respectively. T he apparent Arrhenius activation energy (E-alpha) estimated for the microem ulsion polymerization system was 6.5 x 10(4) J/mol. Also, the morphological parameters were studied at different initiator concentrations. The rheolog ical measurements for the prepared microemulsions were carried out to inves tigate the effect of the preparation parameters on the rheological behavior of the polystyrene microemulsions. The rheological flow curves of the poly styrene microemulsion latices prepared at different temperatures were carri ed out, and we found that the plastic viscosity and Bingham yield values of the flow curves increased with an increasing reaction temperature. That ma y be due to the cage effect of the prepared polymer particles, which trappe d the medium molecules. The plastic viscosity increased with increasing emu lsifier concentration while the Bingham yield value decreased. For the poly styrene microemulsion prepared in the presence of different initiator conce ntrations, the plastic viscosity and Bingham yield increased with increasin g initiator concentration. This trend was found to be the same for the micr oemulsion latices prepared in the presence of different monomer concentrati ons. (C) 2000 John Wiley & Sons, Inc.