The role of high shear in continuous miniemulsion polymerization

Continuous miniemulsion polymerization has been carried out in a single CSTR with both hexadecane (HD) and a polymer as the hydrophobe. Conventional emulsion (macroemulsion) polymerizations using similar recipes exhibit the oscillatory behavior characteristic of micellar nucleation in a CSTR. The lack of such oscillations in the miniemulsion systems, and the observed increases in particle number and rate of polymerization characteristic of miniemulsions, indicate that both the HD- and polymer-stabilized miniemulsion polymerizations proceed via predominant droplet nucleation. In the absence of a high-shear device (sonicator or homogenizer), the systems revert to macroemulsion polymerizations, indicating that the presence of a hydrophobe alone is not sufficient to cause predominant droplet nucleation. Results indicate the viability of using a homogenizer as the high-shear device for miniemulsion polymerization. This is important for scale-up, since sonication on an industrial scale may not be practical.