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THE DRAINAGE AND RUPTURE OF THE FILM BETWEEN COLLIDING DROPS IN THE PRESENCE OF SURFACTANT

The understanding of the coalescence process between two drops is essential in determining the stability of liquid-liquid systems. By solving the equation governing the evolution of the continuous phase film trapped between two drops colliding at constant velocity coupled with that describing the surfactant interfacial concentration in the lubrication approximation, we show that the interface is rendered immobile due to the presence of a small amount of surfactant. Film rupture is therefore delayed due to the Marangoni effect retarding the drainage of the film. In this study, the effects of the viscosity ratio, surface diffusivity, approach velocity and the van der Waals interaction force are reported.