THE EFFECT OF SURFACE-TOPOGRAPHY ON THE ADHESION OF POLY(URETHANE) METAL CONTACTS

This paper describes the results of five types of experiment where a poly(urethane) is adhered to a metal substrate. The adhesion has been quantified by using the 'blister test' and data are given for the interface peeling energy at the same crack velocities to account for the pronounced viscoelastic character of the crack propagation process. The five types of interface studied were prepared as follows using a number of topographically characterized metal substrates. The polymer was cured against these substrates and the fracture energy measured (type 5). The experimental method allowed the interface to be re-formed without a major geometric relocation of the original juxtaposition of the prepared interface. These interfaces were ruptured and the peeling energy quantified (type 1). Alternatively, the interface was re-formed at a position different to the original juxtaposition and peeled apart (type 2). The third and fourth configuration (types 3 and 4) involved the creation and rupture of interfaces of differing combined topographies which had been re-formed following rupture. There are two extremes: a relatively smooth metal in contact with elastomers of a range of roughness and vice versa. The experimental data from the five cases show characteristically different trends and the origins of these trends are considered. The type 3 data are found to follow the predictions proposed and established elsewhere based upon a model of adhesion which incorporates surface free energy and stored elastic strain at asperity contacts. The other types of data indicate that, for these systems at least, the introduction of roughness reduces the strength of the interfaces.