An experimental investigation of the dynamic contact angle in liquid-liquid systems

Abstract

We report measurements of dynamic contact angles performed during the displacement of silicone oil/air and silicone oil/glycerin interfaces in capillary glass tubes. The data obtained for the liquid/air interfaces are in good agreement with other experiments performed by other authors. They also agree with the so-called Hoffman-Tanner law, and with theoretical estimates done by Cox. On the other hand, results obtained with liquid/liquid interfaces show a systematic increase of the dynamic angle compared to theoretical predictions. There are two possible explanations of this fact, which is also reported by other authors. One of them is related to the additional energy dissipation occurring when the contact line moves on a heterogeneous surface. The other one is based on molecular dynamics simulations by Robbins and Thompson, and relies on the influence of slip boundary conditions on the dynamic angle.