Wetting solid surfaces

D. W. Dwight, M. E. Counts, and J. P. Wightman, Colloid and Interface Science, Vol. ni. Adsorption, Catalysis, Solid Surfaces, Wetting, Surface Tension, and Water, Academic, New York, 1976, p. 143. 

An accurate formulation handling is extremely useful not only to make microemulsion and to adjust their properties such as their solubilisation ability, or to attain a low interfacial tension to ease emulsification or to enhance oil recovery. Formulation has been shown to be also directly linked with emulsion properties such as their type, stability, viscosity, drop size [6] and with the efficiency of the emulsification protocol [7]. The existence and persistence of foams are dependent on formulation too [8]. Solid surface wetting is also linked with formulation as well as with many related applications. This is why an accurate numerical treatment of formulation issues is paramount in industrial research and development. 

This commentary on the current status of research on heats of immersion begins where our review written in 1958 concludes [6]. The classification of heats of immersion of solids into liquids as a function of precoverage is expanded to include two new types of curves. Several difficulties in heat of immersion research are discussed. Then, current applications of heats of immersion to determine the average polarity of solid surfaces, heterogeneities on solid surfaces, wetting by surfactants, hydrophilicity of solid surfaces, and thermodynamics of the specific interaction of molecules from solution onto solid surfaces are described. 

Equation (8.1) shows that spontaneous (without work applied to the boundary) solid surface wetting by the composition in aqueous medium is possible for equality of surface tension values in adhesive and liquid, i.e., for -Ycv = 0- The maximum attainable t c,w is advisable, however, as it is in direct proportion to thermod5mamic work of adhesion. Therefore, it is impossible to ensiu-e high-quahty impregnation of porous materials with organic compositions without application of work to the composition-solid boundary, even if the thermodynamic conditions for selective wetting of material pores by the composition... 

Not all surfaces exhibit surface melting it appears to depend on the specific free energy Ay that the dry solid surface has in excess of a solid surface wetted by its own liquid. For positive values of Ay, the surface lowers its free energy by melting for negative values, it stays dry. The condition for surface melting is more readily fulfilled for open surfaces such as fcc(l 1 0) than for close-packed ones. In accordance... 

Figure C2.11.8. An illustration of the equilibrium contact (i.e. wetting) angle, ( ), fonned by the balance of interfacial energies for or a liquid (sessile) drop on a flat solid surface.

Telia F D, Ercolessi F and Tosatti E 1995 Maximum overheating and partial wetting of nonmelting solid surfaces Phys. Rev. Lett. 74 3201... 

The relationship between wetting and solid surface energy... 

The phenomenon of wetting of a solid by a liquid depends on the surfaces and interfacial energies. When a liquid droplet is in contact with an ideally smooth solid surface, as shown schematically in Fig. 9, according to the Young s equation [72], the contact angle (6) of the liquid is given by... 

Detergency may be defined as the removal of dirt from solid surfaces by surface chemical means [29], and may be related to several surfactant properties, including wetting and rewelting ability, foam generation, and surface and interfacial tension. It has long been observed... 

For the solid-liquid system changes of the state of interface on formation of surfactant adsorption layers are of special importance with respect to application aspects. When a liquid is in contact with a solid and surfactant is added, the solid-liquid interface tension will be reduced by the formation of a new solid-liquid interface created by adsorption of surfactant. This influences the wetting as demonstrated by the change of the contact angle between the liquid and the solid surface. The equilibrium at the three-phase contact solid-liquid-air or oil is described by the Young equation ... 

Besides the spontaneous, complete wetting for some areas of application, e.g., washing and dishwashing, the rewetting of a hydrophobic component on a solid surface by an aqueous surfactant solution is of great importance. The oil film is thereby compressed to droplets which are released from the surface. Hydrophobic components on low-energy surfaces (e.g., most plastics) are only re wetted under critical conditions. For a complete re wetting of a hydrophobic oil on polytetrafluoroethylene (PTFE) by an aqueous solution, the aqueous solution-oil interface tension must be less than the PTFE-oil interface tension... 

Bockris and Parry-Jones were the first to carry out experiments with a pendulum to measure the friction between a wetted substrate and the pivot upon which the pendulum swung. It should be noted that Rebinder and Wenstrom199 used such a device for an objective similar to that of Bockris and Parry-Jones, but they claimed that the characteristics of the pendulum oscillations reflected the hardness of the solid surface. The plastic breakdown determining this would be a function of v and this is a potential-dependent value.100, 01 More extensive determinations were made later by Bockris and Argade200 the theoretical treatment was given by Bockris and Sen.201 In the absence of adjustable parameters in the theory, a good agreement between theory and experimental data was assumed.201 The studies by Bockris and Parry-Jones indicated that the... 

By introducing surfactants, which lower the interfacial tension, it is possible to reduce the work necessary to deflocculate agglomerates. In liquid suspensions the introduction of an interfacial tension depressant facilitates wetting of the solid by the liquid and the displacement of adsorbed gases from the solid surface. Certain solids have adsorbed films whose adhesional forces are so great that they resist all mechanical efforts to displace them. Upon the addition of a surfactant, the Aims are displaced and a solid-liquid interface is achieved (1). 

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