Relaxation processes at fluid interfaces

• Published in: Advances in colloid and interface science 1983-01, Vol.18 (3-4), p.281-301
• Main Authors: van den Tempel, M., Lucassen-Reynders, E.H.
• Format: Article
• Language: English
• ISSN: 0001-8686; 1873-3727
• DOI: 10.1016/0001-8686(83)87004-3

Non-equilibrium surface tensions are of paramount importance in the practical application of surfactants. The value of the dynamic surface tension and the rate at which it approaches equilibrium are determined by relaxation processes taking place in or near the surface. This paper reviews the information obtained from both conventional methods and more recent surface wave techniques. The latter are shown to be particularly suitable to identify and study relaxation processes occurring in time scales ranging from 10−3 to 103 s. No evidence is found for ad - and desorption barriers, which are often postulated when equilibration is found to be slow. It is argued that such slow equilibration is more likely to be caused by structure formation in the surface. Ultralow tensions, in particular, are believed to result from the slow formation of structures resembling lamellar liquid crystals in the surface.