Viscoelastic response of a coarsening foam

Abstract : We have investigated the influence of the coarsening process on the complex shear modulus of three-dimensional aqueous foam. It is shown that the viscoelastic response is governed by a large spectrum of relaxation times and that the complex shear moduli measured as a function of frequency, at different foam ages, can be superposed on a single master curve using a scaling law. These results are in agreement with the hypothesis that aqueous foam can be modeled as an elastic matrix in which isotropic weak regions are dispersed. We find that the relaxation times associated with all of these weak regions must increase with foam age according to a parabolic law.