A new method for measuring the dynamic surface tension of complex-mixture liquid drops

Technical Report · Wed Jun 29 04:00:00 EDT 1994

DOI:https://doi.org/10.2172/110695· OSTI ID:110695

Zhang, X; Harris, M T; Basaran, O A

A simple and accurate technique has been developed for measuring dynamic surface tension. The new technique is based on growing a drop at the end of a fine capillary into another immiscible fluid and can follow the changes in tension at a freshly formed interface during its entire period of evolution. When the relative importance of the surface tension force is large compared to gravitational and viscous forces, shapes of growing drops are sections of spheres and the difference in pressure between the interior and the exterior of the drop {triangle}p is related to the surface tension {sigma} and the radius of curvature R by the static Young-Laplace formula {triangle}p = 2{sigma}/R. In contrast to related work, the new technique can determine the surface tension of an interface with a surface age of a few to tens of milliseconds by measuring transient drop shapes and pressures in 1/6 to 1 millisecond. The capabilities of the new method are demonstrated by performing tension measurements on liquid systems that do not exhibit dynamic surface tension as well as ones that exhibit significant dynamic tension effects. Tension measurements made with surfactant-laden solutions show that variation of surface tension is nonmonotonic in time. In such systems, the dynamic behavior of surface tension is shown to depend upon both the rate of interfacial dilatation and that of surfactant transport. A maximum in the surface tension is attained when the lowering of the surfactant concentration on the drop interface due to its dilatation is balanced by the addition of fresh surfactant to the interface by convection and diffusion.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 110695
• Report Number(s): DOE/OR/21400--T491; ON: DE96000672
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
DROPLETS
MEASURING METHODS
SORPTION
SPHERES
SURFACE TENSION
SURFACTANTS
VISCOSITY