Viscous traction

The interfacial shear viscosities are measured by the deep channel viscous traction surface viscometer (5) at the Illinois Institute of Technology. The oil-water equilibrium tensions are measured by either the spinning drop or the du Nouy ring (6) method. 

Viscosity, defined as the resistance of a liquid to flow under an applied stress, is not only a property of bulk liquids but of interfacial systems as well. The viscosity of an insoluble monolayer in a fluid-like state may be measured quantitatively by the viscous traction method (Manheimer and Schechter, 1970), wave-damping (Langmuir and Schaefer, 1937), dynamic light scattering (Sauer et al, 1988) or surface canal viscometry (Harkins and Kirkwood, 1938 Washburn and Wakeham, 1938). Of these, the last is the most sensitive and experimentally feasible, and allows for the determination of Newtonian versus non-Newtonian shear flow. 

The layer of soft-ice adjacent to an interface may be melted or disoriented by adding LiCl. By this means Blank 2) has shown that the value of E/ of a monolayer of octadecanol to the passage of CO2 could be reduced from about 300 sec. cm. for pure water to only about 30 sec. cm. for 8M LiCl solution. Under the latter conditions we believe that the soft-ice is apparently almost completely melted. A small amount of methanol in the water penetrates and somewhat disrupts the film of octadecanol, and Ri again drops from 300 sec. cm. to about 30 sec. cm. i, though with further increase in the methanol concentration the resistance increases again to about 500 sec. cm., presumably due to the methanol molecules held in or near the surface increasing the viscosity of the soft-ice layer. These interpretations of the experimental data are not those proposed by Blank, and further studies with a viscous-traction surface-viscometer (1) should certainly be carried out to test this soft-ice theory. 

When a material is subjected to a tensile or compressive stress, Eqs. (5.63) through (5.74) should be developed with the shear modulus, G, replaced by the elastic modulus, E, the viscosity, rj, replaced by a quantity known as Trouton s coefficient of viscous traction, k, and shear stress, r, replaced by the tensile or compressive stress, a. It can be shown that for incompressible materials, k = 3r], because the flow under tensile or compressive stress occurs in the direction of stress as well as in the two other directions perpendicular to the axis of stress. Recall from Section 5.1.1.3 that for incompressible solids, E = 3G therefore the relaxation or retardation times are k/E. 

Iv) Ion transport, which in the bulk proceeds by conduction, is considerably modified by the presence of the particle. When, as will be assumed here, the particle is kept stationary, the electric force exerted on the countercharge sets this charge into motion. By viscous traction liquid is entrained. This phenomenon is called electro-osmosis-, it will be treated in sec. 4.3b. 

Interfacial Viscosity. In a clean system in which two pure liquids produce an interface, the viscosity of the interface should be the same as the bulk solution viscosity. However, surfactant or impurity adsorption at an interface can cause a resistance to fiow to occur that can be measured as the interfacial shear viscosity. This viscosity is defined as the ratio between the shear stress and the shear rate in the plane of the interface (12), Methods used to make these measurements include a viscous traction surface viscometer (J2), droplet-droplet coalescence (J3), the rotating ring viscometer (14), and surface laser light scattering (9). 

Brookfield Measure viscous traction on spindle rotating in sample... 

Wasan et al. (163) used a deep-channel viseometer in studying the interfaeial shear viseosity of Salem crudes/water with and without the addition of petroleum sulfonate and salts, as well as Illinois erude/brine with pen-tadecyl benzenesulfonate. They showed a decreased coalescence time with decreased shear viseosity. A viscous traction shear viscometer was used for fraetionated crude oil/brine by Pasquarelli and Wasan (164), who showed that increased interfacial shear viseosity is eorrelated with decreased coalescence. Later, Wasan eorrelated interfacial shear viscosity with film-drainage time to determine effective demulsifiers (178). 

Trouton FT (1906) The coefficient of viscous traction and its relation to that of viscosity. Proc R Soc A77 426-440... 

Interfacial shear viscosity measurements were made on the viscous traction shear viscometer developed by Wasan et al. (25) for determining interfacial viscosities of crude oil-aqueous systems. 

Interfacial viscosity measurements Interfacial viscosity (IFV) was measured using a viscous-traction interfacial viscometer constructed according to Wasan (16). Teflon particles were used to measure the centerline velocity of oil/water interface. 

Systems D and E are crude oil-brine-surfactant systems, with System D involving Witco 10-80 surfactant and System E the Exxon C-12 orthoxylene sulfonate system. The large amount of surfactant and alcohol used in System D was to insure a large middle phase volume, the latter being required for interfacial viscosity measurements on a viscous traction instrument. 

In the last five columns we provide the values of the interfacial mobility parameter n (here n corresponds to power in t F R ), the predicted ratio of the surface viscosity coefficient ri and the critical collapse distance 6, the predicted individual values of ri and 6, and, where available, values of r] = K +e or obtained by direct methods. In the latter cases, the r data were obtained from a drop deformation method (17,18), and the e data from tests in a viscous traction instrument (20). 

---