SPREADING OF A DROP BETWEEN A SOLID AND A VISCOUS POLYMER

We consider, for instance, a water droplet (viscosity eta(w)) which tends to wet completely the interface between a hydrophilic solid and a polymer melt (of high viscosity eta(p)). From the Huh-Scriven analysis, we expect two regimes of spreading: (1) when the dynamic contact angle theta is larger than R-1/3 (where R = eta(p)/eta(w)), the velocity U of the contact line should be independent of theta and the radius of the wet patch Q should increase linearly in time rho = Ut; (2) when theta < R-1/3, we return to the standard Tanner law U approximately theta3 and rho approximately t1/10.