Thin-film drainage

Thin-film dewetting, 7 409 Thin film drainage, 12 13 Thin-film evaporators (TFE), 15 259... 

In summary, the results of our thin film drainage study as well as our investigation of oil spreading mechanisms and frequency dependence of dynamic interfacial tension all suggest that the C 2 0S system, which displays the m.ost unstable foam behavior in the presence of oil, should not perform as effectively as the Ci6A0S system in oil displacement experiments in porous media. 

Ivanov, LB. and Dimitrov, D.S., Thin film drainage, in Thin Liquid Films, Ivanov, I.B., Ed., Marcel Dekker, New York, 1988, p. 379. 

Figure 5. Gibbs—Marangoni effect in the thin-film drainage process. Surfactant is swept to the Plateau borders by flow in the film and droplet phases, and thereby create surface concentration gradients that engender surface tension gradients.

Figure 8. Thin-film drainage tune (x) and dilatational modulus (m) at 10 s 1 bubbling frequency of a-olefin sulfonate solutions as a function of surfactant chain length. (Reproduced from reference 22. Copyright 1986 American Chemical Society.)...

The theoretical findings of thin-film drainage models clearly suggest the important role that surface viscosities and elasticities play in foam sta-... 

Film Drainage The drainage of liquid from a lamella of liquid separating droplets or bubbles of another phase (i.e., in a foam or emulsion). Also termed thin film drainage. See also Fluid Film. 

As sedimentation proceeds, a cream can form and drop aggregation and disproportionation (Otswald ripening) can take place (97). The sedimentation step terminating the approach of neighboring drops ends up in a complex dampening process, which may leave a thin film between the drops (98). Numerous factors, from external phase fluid properties to interfacial properties and dynamic effects, can influence the thin film drainage. This is a very active area of research and many of the complexities have been understood (71, 72, 98, 99). However, these phenomena are too complex and intricate to be amenable to straightforward fonnulator handbook recipes. 

IB Ivanov, DS Dimitrov. Thin Film Drainage. In IB Ivanov, ed. Thin Liquid Films — Fundamentals and Applications. Surfactant Science Series, Vol 29. New York Marcel Dekker, 1988, pp 379—85. 

SAK Jeelani, S Hartland. Effect of Interfacial Mobility on thin Film Drainage. J Colloid Interface Sci 164 p 296—... 

Effect of Surfactants on Drop Stability and Thin Film Drainage... 

In the paper Effect of Surfactants on Drop Stability and Thin Film Drainage presented by Professor Krassimir Danov (Sofia University, Bulgaria) the stability of suspensions/emulsions is under consideration. Traditional consideration of colloidal systems is based on inclusion only Van-der-Waals (or dispersion) and electrostatic components, which is refereed to as DLVO (Derjaguin- Landau-Verwey-Overbeek) theory. Professor Danov s contribution shows that not only DLVO components but also other types of the inter-particle forces may play an important role in the stability and colloidal systems. Those contributions are due to hydrodynamic interactions, hydration and hydrophobic forces, steric and depletion forced, oscillatory structural forces. The hydrodynamic and colloidal interactions between drops and bubbles emulsions and foams are even more complex (as compared to that of suspensions of solid particles) due to the fluidity and deformability of those colloidal objects. The latter two features and thin film formation between the colliding particles have a great impact on the hydrodynamic interactions, the magnitude of the disjoining pressure and on the dynamic and thermodynamic stability of such colloidal systems. 

Thin film drainage has been investigated in detail both theoretically and experimentally [22, 28-30, 35]. An extensively applied physical model of a draining thin film is the one of Reynold s, a form of which is shown in Equation 1 ... 

Chapter 5 (Section 6) described the conditions when a thin liquid film could become unstable and rupture and thereby cause coalescence of bubbles or drops. Instability was possible when the film became thin enough (less than 100 nm) for the disjoining pressure effects to be significant. However, considraable time may be required for the film to drain to this thickness, so that the rate of drainage has an important influence on the coalescence rate. The literatnre on expmmental and theoretical aspects of thin film drainage is extensive (Exerowa and Kruglykov, 1998 Ivanov and Dmitrov, 1988). 

Danov, K.D., Effect of surfactants on drop stability and thin film drainage, in Fluid Mechanics of Surfactant and Polymer Solutions, Starov, V. and Ivanov, LB. (Eds.), Springer, New York, 2004, p. 1. 

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