Coalescence in emulsions containing inviscid drops with high interfacial mobility

Ph.T. Jaeger, J.J.M. Janssen, F. Groeneweg, W.G.M. Agterof

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25 Citations (Scopus)
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Abstract

The drainage process of a thin liq. films between 2 droplets of low viscosity is analyzed to specify conditions for coalescence. The time available for film drainage is detd. by the duration of a collision. A. K. Chesters (1975) considered a similar problem and obtained an expression for the rate of drainage which neither contained the extent of flattening of the droplets nor the strength of the flow field. The same hydrodynamic anal. was used to evaluate the rate of drainage in the case of fully mobile interfaces at a vanishing viscosity ratio for the dispersed and continuous phase, from the balance of the driving and resistance forces of the film drainage. In the 1st stage of film drainage, the droplets remain perfect spheres. Once the pressure in the film exceeds the Laplace pressure, deformation sets in. The extent of flattening follows from an energy equation. The drainage process is described by 2 dimensionless parameters, the Capillary no., which gives the strength of the flow field, and the Flow no., which is the ratio of the hydrodynamic and van der Waals forces. The time available for film drainage is obtained from the duration of a collision, which is detd. by the rotation of the collision doublet. Flattening of the droplets retards drainage and reduces the coalescence probability considerably above a value of 0.02 for the Capillary no. Generally, drops with fully mobile interfaces have a much higher coalescence probability than those having rigid interfaces. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)255-264
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume85
Issue number2-3
DOIs
Publication statusPublished - 1994

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