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 spit e of much intense research, the mechanism of foam stability is still not co mpletely clear. Foam stability depends on many parameters but the type of t he added surfactant and the surface rheological properties of the adsorptio n layers play the most important role. Because of the lack of reliable surf ace rheological data a comprehensive investigation of this problem was not yet possible. However, we can now present measurements of surface dilationa l 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 compa red with measurements of foam stability. This indicates that the surface di lational viscosity plays an important role in the stability of foam films. A direct relation between surface dilational elasticity values and foam sta bility could not be detected for the examined systems. Pure elastic adsorpt ion layers were not able to stabilize foam lamellas. (C) 2000 Elsevier Scie nce B.V. All rights reserved.