The Role of Surface Transport in the Stability and Breakdown of Foams

Abstract

A new theory of foam stability is proposed which demonstrates that the transport of substrate. accompanying a movement of the surface of the bubble film, is a dominant factor in the stability of foams and in the action of foam breakers. The surface moves from a region of low surface tension (high surface pressure) to a region of high surface tension. The surface tension gradients arise from disturbances which may be caused by mechanical or thermal shocks, or by the addition to the surface of particles, droplets, or vapour of a surface-active material. When the surface tension is highest at the centre of disturbance the film mill be stable ; when the surface tension is lowest at this point the surface film and hence the substrate will be moved away from this point and the film will rupture.