SEEDED EMULSION POLYMERIZATION OF BUTADIENE .2. EFFECTS OF PERSULFATEAND TERT-DODECYL MERCAPTAN

The kinetics of the emulsion polymerization of butadiene at 60-degrees -C in Smith-Ewart interval III were investigated using sodium peroxodi sulfate (persulfate) as initiator. The aim of this work was to elucida te and model the persulfate initiator efficiency. Monomer conversion w as based on gravimetrically calibrated on-line densitometry. Plots of the product of the propagation rate coefficient, k(p), and the average number of radicals per particle, nBAR, versus initiator concentration showed minimal dependence on the initiator concentration if tert-dode cyl mercaptan (TDM) was present during polymerization. These results c ould not be modeled using normal emulsion polymerization theory. The m odel used in the absence of TDM fits two separate sets of data, nBAR v ersus particle diameter and nBAR versus initiator concentration. In th e absence of TDM, nBAR depends strongly on the initiator concentration . The significant effect of TDM is ascribed to a decrease in the radic al desorption. A possible effect on the radical absorption is refuted on the basis of theory and experiment.