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

Abstract

The kinetics of the emulsifier free seeded polymerization of butadiene at 60 O C in SmithEwart interval I11 was investigated using sodium peroxodisulfate as initiator. The aim of this work was to measure the propagation rate coefficient (k,) of butadiene at 60 "C in emulsion polymerization. Modelindependent techniques to measure propagation rate coefficients like spatially intermitted polymerizationsl-3 ("rotating sector" and "laser flash" photolysis) have not been used for butadiene so far since network formation prevents acquiring the necessary data from GPC. All experiments were conducted in the presence of tertdodecylmercaptan, as is usual in industrial practice. The fractional conversion was b d on gravimetrically calibrated on-line densitometry and was found to be highly accurate. By analogy with the well-known Ugeletad plots, the product of the propagation rate coefficient (k,) and the average number of radicale per particle (e) versus seed latex particle diameter clearly shows Smith-Ewart case I and case I1 regimes. From a constancy in values of kpR (case I1 regime) in this plot, a value for k, could be calculated that was 3 times larger than the current literature value. It was found that negligible "thermal background initiation" is present in the butadiene system. Two linear regions in polymerization rate are observed in interval 111. Model calculations are presented in excellent agreement with the experimental data. From these calculations a value of the rate coefficient for transfer to monomer, k,,, could be estimated.

Ab initio RAFT emulsion polymerization of butadiene using the amphiphilic poly(acrylic acid‐b‐styrene) trithiocarbonate as both surfactant and mediator

“…Also, the monomer concentration used in the calculation could be of error, considering that the interfacial tension in the current cases could be much higher than that using SDS as surfactant. With increase of particle sizes, n increased, in agreement with the previous report on the conventional emulsion polymerization of butadiene 41. This dependence of n on particle size is ascribed to the exit of monomer radical derived from monomer transfer.…”

Synthesis and cross-linking of polyisoprene latexes

“…Values of k p for butadiene (which might have a similar k p to that of isoprene) have been reported in a single early PLP study [22], but these PLP measurements do not satisfy the IUPAC reliability criteria [30,31] established after that work appeared, and difficulties with these data have been revealed [32]. Moreover, these data give a value of k p at 60 8C of 2.0 £ 10 2 M 21 s 21 , contrasting with a value of 3.2 £ 10 2 M 21 s 21 inferred from emulsion polymerization wherein it appeared that the system had reached the plateau where n ¼ 1=2; [33], whence kp can be inferred from the polymerization rate. Morton et al [34] inferred values of k p from overall polymerization rates by assuming this limiting value of n ¼ 1=2; but there was no reliable test of this assumption in their treatment.…”

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

“…The deduction of k,a from the slopes of curves of -In ( 1 -x ) versus time (the left-hand side of eq 3) is elaborately discussed elsewhere. 16 The results are shown in Table V and Figure 6.…”

“…The entry model for absorption of radicals into latex particles for persulfate-initiated emulsion polymerization, as reported by Maxwell et a1., 16 describes the mechanism of entry as follows. A sulfate radical dissolved in the water phase will react with monomer also dissolved in the water phase and form oligomeric radicals.…”

“…The value for z used is 3 monomer units, calculated from a method described by Maxwell et aZ. 16 In Figure 5 model calculations of the entry rate coefficient using the full eq 8 (the new limit is not incorporated) are shown for the widest range in initiator concentration which is still physically feasible.…”