Measuring monomer partition coefficient

A high-pressure unit with on-line sampling of the aqueous phase has been developed to measure monomer partition coefficients [19]. Eig. 14.4 shows a schematic set-up of the equipment and a description of the relevant components and features. With this equipment, the partition coefficient m2 given by Eq. (7) can be measured as a function of pressure and temperature. 

Figure 8. Simulated and measured values of the apparent HCB-soil distribution coefficient (K ) as a function of Tween 80 concentration and the HCB-monomer partition coefficient (K. Input parameters CMC = 35 mg/L b = 8.0 L/g = 5.99 g/kg Kj, = 403.4 L/kg = 0.0 Ldcg = 0.09 L/kg.

Barrett and Thomas (10)proposed that these effects of differential monomer adsorption could be modeled by correcting homogeneous solution copolymerization reactivity ratios with the monomer s partition coefficient between the particles and the diluent. The partition coefficient is measured by static equilibrium experiments. Barrett s suggested equations are ... 

In order to develop efficient post-polymerization and devolatilization operations, it is critical to know where the residual monomer and VOCs are located, that is, if they are mainly in the polymer particles or in the aqueous phase. Table 18.1 (in Section 18.4.2.1) summarizes the partition coefficients (defined as the ratio between the concentrations of monomer/VOC in the polymer particles and in the aqueous phase) measured for several monomers and VOCs in latexes. It can be seen that the monomers are mainly located in the polymer particles. On the other hand, water-soluble VOCs such as acetaldehyde and tert-butanol are mainly in the aqueous phase. It is worth pointing out that the partition coefficient decreases (that is, the monomer partitioning shifts toward the aqueous phase) as the average monomer concentration in the system decreases [56, 57]. 

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