Interfacial Rate Processes in Adhesion and Friction

Adhesion between solid materials results from intermolecular interactions. The fracture resistance of an adhesive joint is, however, determined jointly by the mechanical deformation in the bulk material and the strength of the interfacial bond. The force needed to break an interfacial bond does not have a fixed value; it depends on the thermal state of the system and the rate at which the force is transmitted to the bond. The concomitant energy dissipation arising from the extension and the relaxation of the interfacial bonds contributes a significant resistance to fracture, which is clearly evident in elastomeric polymers. This issue of interfacial dissipation and its relationship to the length of the interfacial bridges and the rate of crack propagation are addressed with the kinetic theory of bond rupture in the tradition of the models developed by Eyring, Tobolsky, Zhurkov, Bueche, Schallamach, Kausch, and more recently, by Evans and Ritchie. Next, the method is extended to address the velocity-dependent sliding friction of elastomers against low energy solid surfaces. The theme of this article is to point out that certain aspects of adhesion, friction, and fracture may be described under a generalized framework of interfacial kinetics.