Seeded emulsion polymerization of butadiene. 2. Effects of persulfate and tert-dodecyl mercaptan

The kinetics of the emulsion polymn. of butadiene at 60 Deg in Smith-Ewart interval III were investigated using sodium persulfate as initiator. Monomer conversion was based on gravimetrically calibrated online densitometry. Plots of the product of the propagation rate coeff., Kp, and the av. no. of radicals per particle, .hivin.n, vs. initiator concn. showed minimal dependence on the initiator concn. if tert-dodecyl mercaptan (I) was present during polymn. These results could not be modeled using normal emulsion polymn. theory. The model used in the absence of I fits 2 sep. sets of data, .hivin.n vs. particle diam. and .hivin.n vs. initiator concn. In the absence of I, .hivin.n depends strongly on the initiator concn. The significant effect of I is ascribed to a decrease in the radical desorption. A possible effect on the radical absorption is refuted on the basis of theory and expt