Effect of Temperature on the Friction and Wear of PTFE by Atomic-Level Simulation

The tribological behavior of oriented, self-mated poly(tetrafluoroethylene) (PTFE) sliding surfaces is examined as a function of temperature from 25 to 300 K. Three distinct sliding configurations are considered: sliding perpendicular to the chain alignment in both PTFE surfaces, sliding parallel to chain alignment in both PTFE surfaces and sliding parallel to the chain alignment on one surface but perpendicular to chain alignment on the other. Our simulations reveal a general trend of increasing friction coefficient with decreasing temperature for configurations where the chains are aligned in the direction of sliding or crossed. However, for conditions where the chains are aligned but the sliding motion is perpendicular to this alignment, gross deformation and athermal friction behaviors are observed. The atomic-level processes associated with these increases in friction at low temperatures are characterized.