Surfactant solutions and porous substrates: spreading and imbibition.

摘要: In Section 1, spreading of small liquid drops over thin dry porous layers is investigated from both theoretical and experimental points view [V.M. Starov, S.R. Kosvintsev, V.D. Sobolev, M.G. Velarde, S.A. Zhdanov, J. Colloid Interface Sci. 252 (2002) 397]. Drop motion a layer caused by an interplay two processes: (a) the drop already saturated parts layer, which results in expanding base, (b) imbibition into substrate, shrinkage base wetted region inside layer. As result these competing processes, radius goes through maximum value time. A system differential equations has been derived to describe evolution with time radii This includes parameters, one accounts for effective lubrication coefficient other combination permeability capillary pressure Two additional experiments were used independent determination parameters. The does not include any fitting parameter after parameters are determined. Experiments carried out on silicone oil various microfiltration membranes (permeable normal tangential directions). monitored. All data fell universal curves if appropriate scales plot dimensionless predicted relationships accounting quite satisfactory data. According theory predictions [1]: (i) dynamic contact angle dependence same as before should be function, (ii) change rapidly initial short stage remain constant duration rest process. constancy this nothing do hysteresis angle: there no under investigation. These conclusions again good agreement observations 2, investigations reviewed aqueous SDS solutions substrates (nitrocellulose membranes) case partial wetting [S. V. M. Spreading nitrocellulose membranes. 264 (2003) 481-489]. was monitored area substrate. total process subdivided three stages-the first stage: expands until reached; decreases during stage; second remains linearly time; third shrinks constant. substrate expends whole Appropriate Experimental showed 481-489]: overall solution increase surfactant concentration; difference between advancing hydrodynamic receding angles concentration increase; angle, but determined reasons. It shown using nonporous that static equal zero, supports conclusion nature substrates. 3, developed spontaneous hydrophobic capillaries, takes account micelle disintegration decreasing close moving meniscus adsorption, well surface diffusion molecules [N.V. Churaev, G.A. Martynov, V.M. Z.M. Zorin, Polym. 259 (1981) 747]. nonionic solution, Syntamide-5, hydrophobized quartz capillaries. rise capillaries presented, connects adsorption front bare interface [V.J. 270 (2003)]. 4, [V. Straov, S. 273 (2004) 589]. Cylindrical model media treatment problem. averaged pore size medium below critical value, then influenced presence surfactants at concentration: moves exactly way pure water. inner pores. If bigger than increases concentration. observations. 5, surfaces considered 227 (2000) 185]. Water droplets wet virgin solid transfer water droplet onto changes characteristics three-phase line. solid-vapor interfacial tension hydrophilise initially just drop. causes spread compared assumption controls rate confirmed 6, polar analyzed when amphiphilic (or their fragments) capable overturning, resulting hydrophilisation Rudoy, V.I. Ivanov, (Russian Academy Sciences English Transaction) 61 (3) (1999) 374]. Such situation may take place, example, polymer whose macromolecules have hydrophilic side groups rotating around backbone polymers containing surface-active additives or Langmuir-Blodgett films composed molecules. possible only lateral interaction neighbouring groups) place. "the overturning state" some distance line making it partially hydrophilic. quantitative describing kinetics allowance mechanism self-organization droplet.