Adhesion and Deformation Friction of Polymer on Hard Solids

Abstract

The main objective of this paper is to present a detailed view of various aspects of adhesion and deformation friction based mainly upon the research findings of this laboratory. An attempt is also made to analyse the large number of results reported elsewhere in order to develop a coherent presentation. Certain fundamental aspects of friction are discussed at first from a phenomenological point of view. A discussion of the law of friction relating to motion follows with a study of the stick-slip phenomena. The next part deals with the isothermal adhesive friction of elastomers on nominally flat and smooth surfaces. Various factors such as physico-chemical nature, sliding speed, temperature, pressure and viscoelastic properties are studied. A quantitative theory to predict the frictional behaviour from physical data specifying the above factors is given along with experimental results obtained in support of the theory. For a given friction pair and normal load, dependence upon the speed and temperature may be calculated from the viscoelastic functions. The magnitude of the friction coefficient in a given viscoelastic state depends upon surface adhesion, which in turn is related to contact angle data, and upon the real area of contact which may be evaluated from elastic and surface statistical data. Certain other factors influencing friction such as the presence of water film and an applied electrical potential are briefly considered. Finally the deformation friction arising from inelastic behaviour of materials is considered along with a discussion of existing theories.