FRICTIONAL PROPERTIES OF POLYETHYLENES AND PERFLUOROCARBON POLYMERS
NAVAL RESEARCH LAB WASHINGTON DC
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Friction was measured at 25 C for steel sliding on polytetrafluorothylene TFE, a copolymer of tetrafluoroethylene and hexafluoropropylene FEP, three high-density polyethylenes HDP, and two low- density polyethylenes LDPat a velocity of 0.01 cmsec and with a load of 1000 grams. The static coefficient of friction with a clean steel slider for all the polymers and the kinetic co efficient of friction for LDP are of the order predicted by the adhesion theory. The experimental values of kinetic coefficient of friction are much smaller than the calculated values with TFE, FEP, and HDP because of the low specific adhesion between these polymers and their films which have transferred to the steel slider. The value of kinetic coefficient of friction for FEP was found to be greater than that of TFE by a factor of three. Similarly, kinetic coefficient of friction for LDP was three times that of HDP. These large differences are explained by the differences in the nature of the transferred polymer films and real areas of contact. All these polymers are potentially excellent dry-film lubricants when used as thin films on a hard backing.
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