Emulsifier mass balance

The determination of adsorption isotherms at liquid-solid interfaces involves a mass balance on the amount of polymer added to the dispersion, which requires the separation of the liquid phase from the particle phase. Centrifugation is often used for this separation, under the assumption that the adsorption-desorption equilibrium does not change during this process. Serum replacement (6) allows the separation of the liquid phase without assumptions as to the configuration of the adsorbed polymer molecules. This method has been used to determine the adsorption isotherms of anionic and nonionic emulsifiers on various types of latex particles (7,8). This paper describes the adsorption of fully and partially hydrolyzed PVA on different-size PS latex particles. PS latex was chosen over polyvinyl acetate (PVAc) latex because of its well-characterized surface PVAc latexes will be studied later. 

There are two factors that infiuence the particle formation conditions the adsorption of emulsifier on the droplets, which baves less emulsifier in the aqueous phase to facilitate particle formation-there, and the rate of radical absorption in monomer droplets. The former factor may be evaluated by talcing into account the adsorption isotherm of emulsifier on monomer droplets. Using a modified Langmuir adsorption isotherm in combination with a mass balance gives an expression for the aqueous phase concentration of emulsifier C... 

The number of particles is a function of emulsifier type and concentration and initiator level, although for monomers that obey Case 1 kinetics such as vinyl chloride and vinyl acetate, is almost independent of initiator level (Ugelstad et al, 1969 Friis and Nyhagen, 1973). The calculation of iVp for various reactor operations will he discussed later. The monomer concentration in the polymer particle [Mp] can he obtained using a simple mass balance. Assuming the monomer and pdymer volumes are additive, one obtains the following relationship for the conversion interval,... 

Figure 4.4 Mass balance of reagents and products in the esterification of sucrose with fatty acid methyl ester under solvent- and water-free conditions (125°C, K2CO3, sucrose ester as emulsifier).

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