Génération et rupture de films liquides minces

Abstract : The ephemeral beauty of soap films is not only a source of wonder and poetic inspiration, but also conceals fundamental scientific questions, which are at the heart of various applications, ranging from shampoo formulation to oil recovery. This work aims at understanding how the life of a soap film, from its generation until its rupture, is affected by the physical-chemical properties of the surfactants used to stabilise it.First, I present a stationary model describing the generation of vertical soap films, under the assumption of insoluble surfactants. I show that the film thickness is controlled by both the generation velocity and the film surface elasticity. The model successfully describes experimental data for soluble surfactants, at least when adsorption is slow. I also introduce an original experimental set up for the generation of liquid films stabilised by insoluble surfactants, which are certainly a promising model system. Secondly, I study the time evolution – i.e. the drainage and rupture – of thin films pulled from a liquid bath, starting with the simplified case of pure liquids. Implementing a non-stationary simulation, I am able to predict the lifetime of silicone oil thin films as a function of the generation velocity, which I find in quantitative agreement with experimental data. I then carry out systematic experiments to characterise the drainage of soap films for various generation velocities, environmental humidities and positions in the film. I also demonstrate the influence of dTAB concentration and humidity on film lifetime. Finally, I investigate how surfactant concentration affects the drainage and break-up dynamics of hemispherical soap bubbles at the surface of a liquid pool, which is a system somewhat closer to real foams.
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Lorène Champougny. Génération et rupture de films liquides minces. Mécanique des fluides [physics.class-ph]. Université Paris-Saclay, 2015. Français. ⟨NNT : 2015SACLS221⟩. ⟨tel-01261045⟩

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