An experimental and theoretical approach to the dynamic behavior of emulsions

Document Type

Syllabus

Publication Date

1-1-2005

Abstract

For emulsion stability the surface chemistry, the dynamic of adsorption, the surface rheology, and the physicochemical kinetics are important. In contrast to the large success in industrial application of the emulsion surface chemistry the physicochemical kinetics is almost not used in emulsion technology. Meanwhile, the population balance equation (PBE) enables prediction of the evolution in time for droplet size distribution if the family of subprocesses including droplet aggregation, aggregate fragmentation, droplet coalescence, and droplet (floccula) creaming are quantified. These subprocesses are characterized in PBE by means of kinetic coefficients (kernels). The coupling of these four subprocesses, droplet poly-dispersity, and immense variety in droplet aggregate configurations cause the extreme difficulty in emulsion dynamics modeling (EDM). Three subprocesses, namely aggregation, fragmentation, and creaming, can be quantified. The systematic consideration of these three subprocesses with account for both Brownian and gravitational aggregation is accomplished in this chapter as it is necessary for EDM. In contrast to those three subprocesses, the experimental approach only is effective now concerning the emulsion film stability and coalescence kernel quantification for EDM. Accordingly, an experimental theoretical approach for the coalescence time determination, based on a dilute emulsion characterization in its simplest state, namely at the singlet doublet quasi-equilibrium, is elaborated. Information about elementary acts of coalescence and fragmentation obtained in experiments with dilute emulsion preserves its significance for concentrated emulsion as well. For modeling of nondiluted emulsions the combining of experimental investigation of the simplest emulsion model system with computer simulation accounting for the characteristics of a concentrated emulsion is proposed. Emulsion dynamics modeling combined with experiments using dilute emulsions at singlet doublet equilibrium may result in: (1) the quantification of emulsion film stability, namely the establishment of the coalescence time dependence on the physicochemical specificity of the adsorption layer of a surfactant (polymer), its structure and the droplet dimensions. This quantification can form a base for the optimization of emulsifier and demulsifier selection and their synthesis for emulsion technology applications, instead of the current empirical level applied in the area; (2) the elaboration of a commercial device for coalescence time measurement, which in combination with EDM will represent a useful approach to the optimization of emulsion technology with respect to stabilization and destabilization.

Identifier

85056387166 (Scopus)

ISBN

[9780824726959, 9781420028089]

Publication Title

Emulsions and Emulsion Stability Second Edition

First Page

1

Last Page

106

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