Dynamic Contact Angles in Liquid-Liquid Systems

When a plate is withdrawn or inserted through a liquid-liquid interface, the additional forced required due to surface effects, is measured and reported in form of a dynamic contact angle. In the first set of experiments the case of water advancing into very viscous oils is shown to have dynamic contact angles somewhat larger than the equilibrium values. In the receding case, the meniscus is seen to be unstable.  In the second set, water is replaced with an aqueous polymer (PEO) solution. Significant changes in contact angles are observed but with no obvious signs of shear thinning effects of polymer solutions.  The receding contact lines are unstable but at higher velocities, with probably an increased effect due to elastic recoil.