Frictional properties of plastics

Source abstract

Abstract The frictional properties of a group of linear polymers have been investigated over a range of loads from 0-04 to 10000 g. Deviations from Amontons’s law occur at light loads. At heavy loads the frictional force is proportional to the area of contact. The force per unit area of contact resisting sliding can be calculated from the frictional force, and is found to be roughly equal to the specific shear strength of the plastic itself. This suggests that strong adhesion occurs over the region of contact, and that, during sliding, shearing occurs within the bulk of the plastic rather than at the interface. The corollary to this, the transfer of material between the two surfaces, has been demonstrated. The frictional properties of plastics can thus be explained by the theory developed by Bowden and his co-workers for the friction of metals. An important exception to these conclusions is polytetrafluorethylene. The force per unit area of contact resisting sliding is much less than the shear strength of the plastic itself.