Friction of polymers sliding on smooth surfaces

Friction plots of polymers sliding on smooth metal surfaces are generally characterized by two regions of distinct dependency on the normal load, with low sensitivity at low stress levels followed by a sharp change in the rate of decrease of friction with increasing pressure at levels above the plastic flow limit of the polymer. A simplified model is proposed to describe this behavior which accounts for the effect of the normal load on the growth of the real contact area and the shear stress at the interface between the polymer and the mating surface. The model has a wide generality when expressed in terms of dimensionless variables, allowing to rationalize the friction behavior of different polymers within a single framework