THE THERMODYNAMICS AND WETTING OF REAL SURFACES AND THEIR RELATIONSHIP TO ADHESION

This paper questions the validity of the common practice of applying wettability experiments to a variety of surface problems, including adhesion. Following from a brief consideration of Gibbsian thermodynamics, wettability and the thermodynamic work of adhesion are discussed within the context of the change of state of the thermodynamic system. The results of this discussion are compared with the thermodynamic adhesion models of Fowkes and Good and with current experimental practice. ft is concluded that wetting experiments do not provide an exact means for determining the reversible work of adhesion, even if adsorption is absent, and that interpretation must always refer to models such as those proposed by Fowkes and Good. However, it is shown that these models imply simplifications and approximations that cannot be assessed for the error they produce in the thermodynamic work of adhesion.