Emulsion monomer concentration inside particle

The population balance equations are very general and may be applied to batch, semicontinuous, and continuous emulsion polymerizations. Furthermore, both seeded and ab initio polymerizations are comprehended by Eq. (5) in all (or part) of the three commonly considered polymerization intervals. The following sections show how the different possibilities are reflected in different functional forms of the elements of the matrices O and K and of the vector c. It should be remembered, however, that certain conceivable situations are not comprehended by Eq. (5) for example, if the monomer molecules are not freely exchanged between the latex particles so that the monomer concentration inside each latex particle is determined by its growth history. 

M] in Equation 12.44 has been replaced by [Mp] in Equation 12.45. This makes sense, since the monomer concentration that feeds the radicals in emulsion polymerization (at the appropriate reaction site) is indeed the monomer concentration in the polymer (latex) particles. Since [R] in Equation 12.44 represents total radical concentration, it has been replaced by the product (N n), which represents the total number of radicals present at the reaction site (the main locus of polymerization, which is inside the monomer-swollen polymer particles). is the total number of particles (usually per lit of water) and n represents the average number of radicals per particle. N, Avogadro s number, appears in the equation simply for unit conversion. Needless to say. Equation 12.45 is completely analogous to Equation 12.44. 

The use of Equation 25.21 to estimate the monomer concentration ((M]p = (1 — 4>p)/Vm) inside the latex particles [24, 25] is possibly the weakest point in the contemporary kinetic treatment of emulsion polymerization, as it must be assumed that the monomer is saturated inside the particles and that swelling is fast enough to compete with polymerization kinetics. 

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