Department of Physics Papers

Document Type

Journal Article

Date of this Version

1999

Publication Source

Journal of Rheology

Volume

43

Issue

6

Start Page

1411

Last Page

1422

DOI

10.1122/1.551052

Abstract

We present an experimental study of the rheology of polydisperse aqueous foams of different gas volume fractions φ. With oscillatory deformation at fixed frequency, we determine the behavior of the maximum stress as a function of the strain amplitude. At low strain, the maximum stress increases linearly, defining a shear modulus G.G. At progressively higher strains, the response eventually becomes nonlinear, defining the yield strain and the yield stress. While φ decreases toward φc=0.635±0.01,φc=0.635±0.01, GG goes to zero, and the yield stress decreases by many orders of magnitude with a quadratic behavior. The yield strain, which can be extrapolated to 0.18±0.020.18±0.02 at φ=1,φ=1, has a minimum value of 0.045±0.0100.045±0.010 at φc.φc. This behavior shows the occurrence of a melting transition located at φc,φc, which can be correlated to the random close packing of spheres. We compare these results to similar ones obtained previously for monodisperse and polydisperse emulsions. Our new experiments clarify the rheological similarities between emulsions and foams, as well as the role of polydispersity. We find that as long as polydispersity is moderate, it does not play a crucial role in the elastic response of foams and emulsions.

Copyright/Permission Statement

This article was originally published by the American Institute of Physics. You can find the original article at: http://sor.scitation.org/doi/10.1122/1.551052

Comments

At the time of publication, author Douglas J. Durian was affiliated with University of California Los Angeles. Currently, he is a faculty member at the Physics Department at the University of Pennsylvania.

Keywords

foams, emulsions, yield stress, elasticity, elastic moduli

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Date Posted:10 October 2017

This document has been peer reviewed.