562e Interfacial Tension and Spreading Coefficient for Thin Films, and Lateral Drop Adhesion

Prashant Bahadur¹, Ken G. Pepper², Kumud Chaurasia¹, Preeti S. Yadav¹, and Rafael Tadmor¹. (1) Chemical Engineering, Lamar University, Beaumont, TX 77710, (2) Process Engineering, Chicago Bridge and Iron, 350 Pine Street, Suite 400, Beaumont, TX 77701

We present a modified mathematical expression for the interfacial tension of very thin films. At large thicknesses the modified expression converges to the classic mathematical expression. We use this modified expression to derive an equation for the spreading coefficient as a function of film thickness. The spreading coefficient equation is then used to calculate the equilibrium thickness of a wetting liquid film for a “pancake drop”. Our predictions agree with experimental data. We discuss the applicability of this theory to drop adhesion to surfaces and show some new experimental results.

References:

1. R. Tadmor and K. G. Pepper, “Interfacial Tension and Spreading Coefficient for Thin Films”, Langmuir, 24, 3185, (2008).

2. R. Tadmor, K. Chaurasia, P.S. Yadav P. Bahadur, A. Leh, L. Dang, W. Hoffer, “Drop Retention Force as a Function of Resting Time” Langmuir, 24, in press, (2008).

3. P.S. Yadav, P. Bahadur, R. Tadmor, K. Chaurasia, and A. Leh, “Drop Retention Force as a Function of Drop Size”, Langmuir, 24, 3181, (2008).