Dynamic Contact Angles at Low Velocities

✍ Scribed by R.V. Sedev; C.J. Budziak; J.G. Petrov; A.W. Neumann

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 423 KB
• Volume: 159
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1993.1338

✦ Synopsis

Dynamic contact angles of octane, dodecane, and hexadecane on mica dip-coated with a fluorocarbon polymer were investigated at low velocities. The high precision capillary rise technique was employed to record both advancing and receding angles on dry, prewetted, and soaked surfaces. Repeated measurements on the same sample revealed that, although chemically stable, the polymer surface is affected by its contact with the liquid. Therefore, care should be taken when studying the wetting kinetics in such systems because dynamic contact angles depend not only on the contact line velocity but also on the time of the solidliquid contact and on the local degree of solid surface modification. On well defined (dry or soaked-to-saturation) surfaces neither the advancing nor the receding dynamic contact angles exhibit a velocity dependence up to (0.015 \mathrm{~cm} / \mathrm{s}). On the soaked surface, where the receding angles are meaningful, these velocity independent values are different for the advancing and receding mode. The observed initial plateaux of the dynamic contact angle-velocity dependences could be simulated by the scatter of the experimental data. For particular groups of systems the theoretical predictions give realistic estimates of the velocity at which these "quasi-plateaus" should end, but neither the hydrodynamic nor the molecular-kinetic approach describes satisfactorily all literature data on velocity independent dynamic contact angles. 1993 Academic Press. Inc.