Dynamic Interfacial Tension Measurements by a Capillary Pressure Method

Abstract: A new technique to measure dynamic interfacial tension is presented which represents one of the possible applications of the capillary pressure methods. These methods are based on the direct measurement of the capillary pressure to obtain surface or interfacial tension data by the application of the Laplace equation. The particular approach (expanded drop technique), presented with the relevant experimental details, allows the dynamic interfacial tension of static interfaces (constant interfacial area) to be recorded, as a function of the surface age. This latter property, together with the large mass of data which is possible to collect in a single experiment, makes this technique very attractive in adsorption kinetics studies aimed both at obtaining new experimental data and to test the available theories on the subject. A specific application to the study of adsorption kinetics of Triton X-100 at the n-hexane/water interface is also presented. The results of this study show that for this system adsorption kinetics is, essentially, diffusion-driven. Moreover, these results are in good agreement with the available literature, confirming the reliability of the presented technique.