The role of high shear in continuous miniemulsion polymerization

Continuous miniemulsion polymerization has been carried out in a single CST R with both hexadecane (HD) and a polymer as the hydrophobe. Conventional e mulsion (macroemulsion) polymerizations using similar recipes exhibit the o scillatory behavior characteristic of micellar nucleation in a CSTR. The la ck of such oscillations in the miniemulsion systems, and the observed incre ases in particle number and rate of polymerization characteristic of miniem ulsions, indicate that both the HD- and polymer-stabilized miniemulsion pol ymerizations proceed via predominant droplet nucleation. In the absence of a high-shear device (sonicator or homogenizer), the systems revert to macro emulsion polymerizations, indicating that the presence of a hydrophobe alon e is not sufficient to cause predominant droplet nucleation. Results indica te the viability of using a homogenizer as the high-shear device for miniem ulsion polymerization. This is important for scale-up, since sonication on an industrial scale may not be practical.