FRICTION, ADHESION AND BOUNDARY LUBRICATION OF POLYMERS.

Abstract

This review discusses the mechanism of polymer friction in terms of adhesion and deformation processes. It suggests that the deformation term is the only certain factor that can be directly related to the bulk viscoelastic properties of the polymer. The mechanism of adhesion is then discussed in terms of electric surface charges and van der Waals forces and it is suggested that a simple monistic view is not valid. The adhesion component of friction depends on speed, temperature and contact pressure in a manner implying a close correlation with bulk viscoelastic properties. This appears to be reasonably valid for rubbers but less so for thermoplastics. Reasons for this are discussed and some of the inadequacies of current theories of polymer friction analyzed. In fluid lubrication the importance of wettability and the role of electrical double layers are discussed. Reference is also made to chemical modifications of the surface and to the behavior of polymers containing small amounts of ″dissolved″ additives.