The friction and visco-elastic properties of polymeric solids

• Published in: Wear 1966-01, Vol.9 (5), p.329-348
• Main Authors: Ludema, K.C., Tabor, D.
• Format: Article
• Language: English
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/0043-1648(66)90018-4

This paper describes an attempt to link the frictional properties of polymers with their visco-elastic characteristics. The friction was measured over a speed range of 10 −5−1 cm/sec and over a temperature range of −100°−+200°C. The results show, in agreement with the earlier studies of Grosch, that, for rubber, there is a close relation between the sliding friction at various speeds and temperatures and the viscoelastic properties of the rubber. This may be explained on a very simple model in terms of the way in which the area of contact and the interfacial shear strength vary with rate of deformation and temperature. With polymers below their glass transition temperature there is often a marked variation in sliding friction with speed and temperature but is does not appear to correlate directly with the visco-elastic properties of these materials as determined by conventional methods. On the other hand, the rolling friction correlates very well with the conventional visco-elastic data, showing that the high local pressures at the points of real contact do not appreciably change the visco-elastic characteristics. The lack of correlation with sliding friction must, therefore, be attributed to the extremely high shear strains occurring at the interface during sliding. These deformations, although themselves speed and temperature dependent, bear little relation to the deformation processes involved under the very gentle conditions of conventional visco-elastic investigations. Presumably with rubber, the slip of chain segments over one another remains the basic mechanism of shear even at the high strains involved in sliding. The results suggest that more direct information is required on the viscoelastic properties of polymers when they are deformed under high pressures and at very large strains.