Seeded emulsion polymerization of butadiene. 1. The propagation rate coefficient

The kinetics of the emulsifier-free, seeded polymn. of butadiene (I) at 60 Deg in Smith-Ewart interval III were studied in presence of Na peroxodisulfate initiator and tert-dodecyl mercaptan. The fractional conversion was based on gravimetrically calibrated online densitometry and was highly accurate. By analogy with the well-known Ugelstad plots, the product of the propagation rate coeff. (kp) and the av. no. of radicals per particle (.hivin.n) vs. seed latex particle diam. clearly showed Smith-Ewart case I and case II regimes. From a constancy in values of kp.hivin.n (case II regime) in this plot, a value for kp could be calcd. that was 3 times larger than the current literature value. Negligible thermal background initiation was present in the I system. Two linear regions in polymn. rate were obsd. in interval III. Model calcns. were presented in excellent agreement with the exptl. data. From these calcns. a value of the rate coeff. for transfer to monomer could be estd