Slow viscoelastic relaxation and aging in aqueous foam

Université de Marne-la-Vallée, Laboratoire de Physique des Matériaux Divisés et des Interfaces, UMR 8108 du CNRS - 5 Boulevard Descartes 77454 Marne-la-Vallée cedex 2, France

Received: 5 December 2005
Accepted: 1 March 2006

Abstract

Like emulsions, pastes and many other forms of soft condensed matter, aqueous foams present slow mechanical relaxations when subjected to a stress too small to induce any plastic flow. To identify the physical origin of this viscoelastic behaviour, we have simulated how dry disordered coarsening 2D foams respond to a small applied stress. We show that the mechanism of long time relaxation is driven by coarsening-induced rearrangements of small bubble clusters. These findings are in full agreement with a scaling law previously derived from experimental creep data for 3D foams. Moreover, we find that the temporal statistics of coarsening-induced bubble rearrangements are described by a Poisson process.