The viscoelastic nature of the sliding friction of polyethylene, polypropylene and copolymers

Abstract

According to the adhesion theory of sliding friction, the sliding force or frictional resistance to motion is due to making and breaking of adhesional bonds between the sliding bodies. Thus the sliding force F is proportional to the shear strength S of adhesional bonds and the area of contact A between contacting bodies. This paper reports the results of a study to find the proper relationship between F, A and S. The value of F is taken from a friction test over a sliding speed range of 10,000 to 1 and over a temperature range up to 150[deg]C. The values of A and S are derived from shear tests, also over wide ranges of strain rate and temperature. All data were then subjected to special viscoelastic transformation. It was found that the friction data were transformable by the same transforms applicable to mechanical property data, provided changes in polymer morphology are taken into account. This coincidence is evidence of a strong connection between A, S and F which lends support to the adhesion theory of friction.