Emulsion polymerization of butadiene, 3. Kinetic effects of stirring conditions and monomer/water ratio

Abstract

Abstract The stirring speed n influences the emulsion polymerization of butadiene, (1) by reducing the effective emulsifier concentration [E] eff available for particle nucleation and stabilization at high n , and (2) by limiting diffusion of monomer to the latex particles at low n . The large density difference between butadiene and water promotes the breaking up of droplets at high n , while the same condition constitutes a large driving force for (partial) phase separation at low n . Increasing the monomer/water ratio at constant [E] decreases [E] eff , and thus the final particle number. At monomer volume fractions >0,6 mixed emulsions are likely to be formed initially, reducing [E] eff even further. In the presence of mixed emulsions, polymerization in the monomer phase may no longer be neglected, giving rise to a complex kinetic behaviour.