Relationship between surface dilational properties and foam stability

The knowledge of the stability of foams and emulsions is very important for the control of a large number of technological processes. However, in spite of much intense research, the mechanism of foam stability is still not completely clear. Foam stability depends on many parameters but the type of the added surfactant and the surface rheological properties of the adsorption layers play the most important role. Because of the lack of reliable surface rheological data a comprehensive investigation of this problem was not yet possible. However, we can now present measurements of surface dilational properties of soluble adsorption layers in a frequency range of 1-500 Hz using a new version of the oscillating bubble method. The results are compared with measurements of foam stability. This indicates that the surface dilational viscosity plays an important role in the stability of foam films. A direct relation between surface dilational elasticity values and foam stability could not be detected for the examined systems. Pure elastic adsorption layers were not able to stabilize foam lamellas. (C) 2000 Elsevier Science B.V. All rights reserved.