Surface dilational behaviour of surfactant solutions: A comparison between the overflowing cylinder and the free falling film technique

• Published in: Colloids and surfaces 1992-08, Vol.65 (2), p.191-199
• Main Authors: Bergink-Martens, D.J.M., Bisperink, C.G.J., Bos, H.J., Prins, A., Zuidberg, A.F.
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; Foaming behaviour; free falling film; General and physical chemistry; Geïntegreerde levensmiddelentechnologie en -fysica; Integrated Food Science and Food Physics; overflowing cylinder; surface dilational properties; surface tension gradient
• ISSN: 0166-6622; 1873-4340
• DOI: 10.1016/0166-6622(92)80274-6

Both the overflowing cylinder and the free falling film technique are used to study the behaviour of expanding liquid surfaces far from equilibrium. An important property of an expanding liquid surface is its dynamic surface tension which can be measured by means of the Wilhelmy plate technique. In order to enable measurements in a vertical liquid film the Wilhelmy plate technique was modified in such a way that the dynamic surface tension could be measured along the height of the free falling film. The effect of the observed surface tension gradient on the velocity distribution of the free falling film is calculated. It appeared that the expanding liquid surfaces of the overflowing cylinder and the free falling film apparatus generated the same dynamic surface tension. From this it is concluded that these two techniques physically operate in the same way. It is shown that the behaviour of the overflowing cylinder is governed by the film falling on its outside.