An investigation on the relationships between cohesive energy density and tribological properties for polymer–polymer sliding combinations

The friction and wear behaviors of various polymer–polymer combinations were examined by means of a pin-on-disc type apparatus. The worn surfaces of the polymers were observed by using Scanning Electron Microscope (SEM). The relationships between the tribological properties and cohesive energy density (CED) of the two mated polymers were found. For the similar polymer combinations, the increasing CED of the polymers associated with an increasing friction coefficient but a decreasing specific wear rate. For the dissimilar polymer combinations, the friction coefficient was found to relate to the absolute value of the CED difference of the two mated polymers, that was, the greater the CED difference of the two mated polymers was, the higher the friction coefficient was. The specific wear rates of the polymers increased with the increasing CED of the mated polymers for dissimilar polymer–polymer combinations. Coarse worn surfaces were observed when the two mated polymers with little difference in CED value. It was concluded that the adhesion between the two mated polymers was a main factor for controlling the friction property of a polymer–polymer sliding combination, and the polymer wear was closely related to its shear strength. The reasons why the tribological properties of polymer–polymer combinations related to the CED of polymers were also discussed.