Example kinetic analysis of vinyl chloride polymerization

4 EXAMPLE KINETIC ANALYSIS OF VINYL CHLORIDE POLYMERIZATION 

Each year, hundres of thousands of tons of vinyl chloride are polymerized in the world. Commensurate attention is thus paid to studies of its polymerization. Vinyl chloride is one of those monomers that are transformed to polymer by a complicated mechanism. Poly(vinyl chloride) is soluble neither in its own monomer nor in the common solvents. Its formation is therefore connected with the appearance of a solid phase the process has the character of precipitation polymerization. This greatly complicates the kinetics of solution and bulk (suspension) polymerization. 

Various groups of investigators so far do not agree in their ideas concerning the mechanism by which the polymer particles, swollen by monomer, are formed. To illustrate how the kinetics of a complicated macromolecular synthesis is being analyzed, the approach of the representatives of several laboratories will be presented. 

The polymerization of vinyl chloride evidently proceeds in the monomer phase and in monomer-polymer particles. Crosato-Arnoldi et al. [17] and 

Abdel-Alim and Hamielec [18] assume that the radicals do not diffuse between the various phases. Radicals are generated in monomer medium, and here they also decay, either still in solution or already in the solid phased The active centres, generated in the polymer-phase, decay in the same phase their desorption does not occur [17). When the partition coefficient of the initiator between the monomer and polymer-rich phases is equal to unity we can write 

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