Butadiene polymerization kinetic parameters

Equation (2.26) leads to a solution for from available knowledge of the rate R, the concentration of monomer in the monomer-polymer particles [M], and the number of particles, N. This method has been applied to several monomers and has been especially useful in the case of the dienes, where the classical method of photoinitiation poses difficulties. Some of these results are shown in Table 2.4 in the form of the usual kinetic parameters. The results obtained for styrene by photoinitiation techniques are included for comparison. It can be seen that the agreement is remarkably good, considering the widely different experimental methods used. Recent studies of the emulsion polymerization of butadiene have shown that the rate constant for propagation is even higher than previously estimated (see Table 2.1) (Weerts et al., 1991). 

The free-radical kinetics described in Chapter 6 hold for homogeneous systems. They will prevail in well-stirred bulk or solution polymerizations or in suspension polymerizations if the polymer is soluble in its monomer. Polystyrene suspension polymerization is an important commercial example of this reaction type. Suspension polymerizations of vinyl ehloride and of acrylonitrile are described by somewhat different kinetic schemes because the polymers precipitate in these cases. Emulsion polymerizations aie controlled by still different reaetion parameters because the growing macroradicals are isolated in small volume elements and because the free radieals which initiate the polymerization process are generated in the aqueous phase. The emulsion process is now used to make large tonnages of styrene-butadiene rubber (SBR), latex paints and adhesives, PVC paste polymers, and other produets. 

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