EFFECTS OF SURFACTANT ADSORPTION—DESORPTION KINETICS AND INTERFACIALRHEOLOGICAL PROPERTIES ON THE RATE OFDRAINAGE OF FOAM AND EMULSION FILMS

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Abstract
An analysis has been developed to describe the rate of drainage of an axi-symmetric plane-parallel foam and emulsion films associated with bubble-bubble and drop-drop coalescence phenomena. The present analysis extends the earlier work of Zapryanov et al(1983) and of others which was limited to the diffusion controlled case of the surfactant transport from the bulk phase onto the interface. Here the surfactant transport from the bulk phase to the interface is accounted for by a two step mechanism: (i) diffusion of the surfactant from the bulk to the sublayer, followed by (ii) the adsorption of the surfactant from the sublayer onto the interface. The results of a parametric study indicate that the rate of drainage of surfactant stabilized films is strongly dependent upon the surfactant adsorption-desorption kinetics, selective surfactant solubility, and interfacial Theological properties such as elasticity and interfacial viscosity. Predictions of the film drainage time are compared with our experimental data to establish the range of the applicability of the present model with respect to film radius.

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