SOME REFLECTIONS ON CONTEMPORARY VIEWS OF THEORIES OF ADHESION

This paper reviews the literature on mechanical interlocking and adsorption interactions, the two main mechanisms postulated to account for adhesive bonding. It is shown that interpenetration of adhesive and adherend is important in obtaining optimum adhesion in a wide range of applications. While for fibrous materials this interpenetration is fairly obvious on a macro scale, for metal/metal oxide surfaces it is on a micro scale and revealed by sophisticated surface examination techniques. Wetting and the thermodynamics of solid/liquid interfaces are reviewed and the development of theories relating to secondary interaction forces is discussed Recent evidence for the existence and significance of primary chemical bonding in adhesion is then outlined.