EFFECT OF IONIC SURFACTANTS ON THE STABILITY OF PLANE-PARALLEL FILMS

Abstract. The stability of a partially mobile thin liquid plane-parallel film between two gas or oil phases is studied. The long wave approximation is used to analyze the influence of soluble ionic surfactants and non-surface active background electrolyte on the increment/decrement of fluctuations. The material properties of the corresponding multiphase flow and interfaces are taken into account. The equilibrium state of the film is described by the classical DLVO theory in which the Van der Waals and electrostatic disjoining pressures are included. The fluctuation analysis of the electro-diffusion fluxes, velocity of the components, concentrations, electric potential and film thickness give the analytical criteria for stability of the equilibrium state. Numerical results show changes of the stability region with increasing surfactant concentration and significant influence of the background electrolyte. The stabilizing effects of the Gibbs elasticity, surface and bulk viscosities are demonstrated.. The results are useful for control of the foam breakdown in the industrial systems