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Flocculation and Coalescence of Oil-in-Warer Emulsions

Published online by Cambridge University Press:  25 February 2011

J. Bibette
J. Bibette*
Affiliation:
Centre de recherche Paul-Pascal, Av A. Schweitzer, Pessac F33600 Cedex, France
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Abstract

Emulsions are commonly made of macrosized droplets dispersed in a continuous solvent. These systems are subject to two types of instabilities. One is reversible: flocculation, the other is irreversible: coalescence. The reversible flocculation induced by excess surfactant is studied. It is shown that an attractive interaction arises from depletion of surfactant micelles and leads to a fluid-solid phase transition. The sensitivity of this phase transition to the oil droplet diameter leads to a fractionated crystallisation method for purifying in size highly polydisperse emulsions. These well characterized systems are used to study the stability of the film against coalescence. Two distinct regimes of coalesence are found. One is driven by the surfactant chemical potential and occurs in a dilute emulsion. The other is driven by the water chemical potential and takes place in a concentrated emulsion which ressembles a biliquid foam.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 248: Symposium O – Complex Fluids , 1991 , 303
Copyright
Copyright © Materials Research Society 1992

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