AbstractThe effect of stirring speed on the rate of the persulfate‐catalyzed polymerization of vinylidene chloride has been determined. It was found that the first‐stage rate decreases with increasing stirring speed, that the second‐stage rate increases with increasing stirring speed, and that the rate of the third stage is independent of stirring speed. These results, as well as those of an earlier paper, may be explained in the following manner. The second stage slow‐down results from monomer starvation, caused by slow diffusion from coalesced droplets. Recovery is caused by transfer of monomer at the time of collision between a polymer particle and a monomer droplet. These collisions are allowed when the repulsive forces between monomer droplet and polymer particle are reduced because of surfactant def