ABSTRACT
Adhesion and wetting of solid surfaces are major elds in interface science with a remarkable range of technological applications. In spite their importance, their precise determination still remains a challenge due, primarily, to the challenges associated with the practical implementation of an operational denition of the surface tension, γS, of solids. The latter is often determined from extrapolations from the melt state and, most commonly, indirectly from the contact angle of liquid drops deposited on the surface and the application of a model/equation for the interfacial tension, γSL, with the liquid. In general, the work of adhesion of two unit surfaces or the negative of the surface free energy change upon the formation of a unit interface ij from the component unit surfaces i and j is obtained from the Dupre equation [1,2]:
W Gijadh i j ij ijs= + − = −γ γ γ Δ (11.1)
The work of adhesion of a solid with a liquid, forming a contact angle θ with the solid surface, is given by the classical Young equation [3]:
L= +γ θ( cos )1 (11.2)
As seen, a combination of Equations 11.1 and 11.2 does not give the interfacial tension unless we know the surface tension of the solid surface, and vice versa. The use of additional liquids will provide for more equations, but one unknown will always be left undetermined. Thus, it is essential to have an additional model/equation for the interfacial tension or the work of adhesion.
