Surface energy liquid-solid

Measurement of the contact angle at a solid-liquid interface is a widely used method for the determination of the surface energy of solid polymers. Fowkes [1] first proposed that the surface energy of a pure phase, y y could be represented by the sum of the contribution from different types of force components, especially the dispersion and the polar components, such that ... 

A, Mean free path of ions, meters Am Mean free path of electrons, ions, or molecules, meters a Surface tension of liquid or surface energy of solid, N/meter or J/ meter2... 

When an adsorbing surface is exposed to a gas or vapour adsorption will take place, being accompanied by the absorption or evolution of heat. Such thermal changes have already been noted in the extension and contraction of surface films of liquids. Although the direct determination of the surface energy of solid surfaces presents many experimental difficulties yet of its existence there is no doubt. On the adsorption of a gas or vapour a diminution in the free surface energy of the system likewise occurs. From the Gibbs-Helmholtz relationship dcr... 

Measurement of the surface energy of a liquid is relatively easy to both perform and understand. All methods are based on measuring the work required to create a new surface by transferring molecules from bulk liquid. However, what about the surface energy of a solid Clearly, for solids it is impractical to move molecules from bulk to the surface. There are basically two ways by which we can attempt to obtain the surface energy of solids ... 

The second approach to obtaining the surface energies of solids involves the study of wetting and non-wetting liquids on a smooth, clean solid substrate. Let us examine the situation for a non-wetting... 

Surface Tensions of Liquids and Surface Energies of Solids... 

The work of cohesion of a liquid Wc is defined as that which is required to create two new interfaces with a total interfacial tension of 2y. Under conditions of complete wetting, W. = 2y tTsv, which shows that the work of adhesion for completely wetting liquids is always larger than the work of cohesion. Adhesion problems generally require the consideration of aspects other than wetting alone. An important issue is to determine the surface energies of solids. The surface tensions of liquid-vapour and liquid-air interfaces can easily be determined from the pressure difference across... 

A solid is defined as a material that is rigid and resists stress. A solid surface may be characterized by its surface free energy and surface energy. The surface energy (tension) of a solid caimot be measured in a similar manner to that of a liquid, due to the difficulty caused by the reversible formation of its surface. The methods for the determination of surface energy of solids are described in this chapter. 

The article on Surface energy components describes how surface energies of solids and thence the work of adhesion between adhesive and substrate could be calculated from an assumption that the surface energy is composed of the sum of a dispersion and polar component (Eqn. 9 therein). Practical measurements of surface tensions of liquids and of contact angles of liquids on solids were involved. In a similar way, solid surface energies and works of adhesion can be obtained from the assumption (Eqns. 3 and 4 above) that surface energy is made up of the sum of a Lifshitz-van der Waals and an acid-base component. The term is obtained using non-polar liquids in exactly the same way as the dispersion components, y, were obtained. This article is concerned with expressions that can be used to represent acid-base interactions and which can then be used in equations such as 3 and 4 and those derived from them. 

Once the dispersion component of surface energy of a liquid is known, the polar component can be obtained from the surface tension using Eqn. 10. The approach based on Eqns. 9 and 10 can then be used to estimate surface energies of solids, particularly polymers, very much in the same way as Ys values are obtained from Eqn. 8. Here, yi2 is eliminated between Eqn. 10 and the Young equation, giving... 

Oji is the surface energy of solid-liquid interface is the bulk enthalpy of fusion... 

The surface tension of liquids is easily measured by a wide variety of methods, whereas it is much more difficult to measure the surface energy of solids. A comprehensive overview covering methods applicable for liquids and solids is presented by Adamson [111]. 

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