title: Foam drainage. Possible influence of a non-newtonian surface shear viscosity.
abstract: We describe forced drainage experiments of foams made with model surfactant solutions with different surface rheology. We analyze the origin of two distinct drainage transitions reported in the literature, between regimes where the bubble surfaces are mobile or rigid. We propose that both transitions are related to the surface shear viscosity and to its shear thinning behavior. Shear thinning could also account for the huge discrepancies between measurements reported in the literature. The role of surface tension gradients, i.e. Marangoni effect, could not possibly explain the behavior observed with the different solutions.
authors.affiliation: Laboratoire de Physique des Solides, Université Paris Sud 11, CNRS UMR 8502, Orsay, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Gauchet
authors.affiliation: Laboratoire MSC, Université Paris Diderot, CNRS UMR 7057, Paris, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Durand
authors.affiliation: Laboratoire de Physique des Solides, Université Paris Sud 11, CNRS UMR 8502, Orsay, France. Electronic address: dominique.langevin@u-psud.fr.
authors.forename: Dominique
authors.initials: D
authors.lastname: Langevin
keywords: Foam drainage; Marangoni effects; Surface shear viscosity