Controlling particle size by self-sustained oscillations in continuous emulsion polymerization of vinyl acetate

This work examined the controllability of the size of polymer particles and its distribution by taking advantage of the self-sustained oscillations of monomer conversion in continuous emulsion polymerization of vinyl acetate in a CSTR. The emulsifier concentration was primarily varied as a control parameter of the experimental condition below the critical micelle concentration. Regularly periodical oscillations in monomer conversion occurred with a long period as compared to the mean residence time of the CSTR. Time-dependent size distribution of polymer particles observed by TEM varied in form synchronously with the periodical oscillations of monomer conversion. These results suggest that particles can be formed intermittently owing to the temporal variation of the concentration of free emulsifier in the condition below CMC. It has also been confirmed that the particle size distribution (PSD) is made quite narrow in the condition for regularly periodical oscillations but considerably wide in the condition for irregular oscillations. It has been successfully indicated that the self-sustained oscillations in continuous emulsion polymerization will be profitable not only for controlling the size of latex particles but also for raising the monomer conversion.