Critical bubble diameters and Plateau border dimensions for drainage in aqueous xanthan foams

Abstract Xanthan gum is used to stabilize aqueous foams in a wide number of commercial and industrial processes and is one of the numerous hydrosoluble polymers used to slow foam drainage. The slowing effects of viscosity on drainage flow have been well studied but the situations leading to a drainage delay are poorly described in the literature. The aim of this study was to shed light on the mechanisms governing drainage delay and drainage initiation. Drainage delay seems to be the result of liquid retention caused by the confinement of xanthan molecules in the Plateau borders, which increases local yield stress. Drainage begins when the bubbles and Plateau borders grow above a certain threshold size that allows liquid to flow through the foam.