Self-Lubricating Ultrahigh Molecular Weight Polyethylene Thin Films with Excellent Wear Resistance at Light Friction Loads on Glass and Silicon

Thin films of ultrahigh molecular weight polyethylene (UHMWPE) were prepared on glass and silicon using a dip-coating technique, followed by removal of the decahydronaphthalene solvent at 140 °C for 20 hours and cooling in the oven in air. The wetting ability of the films was investigated by a contact angle method. The tribological behavior of the films was investigated using a ball-on-disk configuration in reciprocating mode. The reciprocating frequency of 4 Hz and single sliding distance of 5 mm used corresponded to a sliding speed of 40 mm/s. The counterface was a GCr15 steel ball with diameter of 3 mm and the normal frictional loads were 10–300 g. The worn surfaces on the films and wear scars on the steel ball were observed and analyzed by scanning electron microscopy (SEM). It was found that the surface morphologies of the films on glass and silicon were different, which is ascribed to the difference in thermal conductivity of the glass and silicon. Evaporation of the solution caused micro-orifices in the films on glass. The water contacting angle of about 87° on the films on the two substrates was similar to that of bulk UHMWPE. Their friction coefficient of about 0.1–0.2 indicated the films were self-lubricating. The wear life of the films decreased quickly with the increase of friction load. At light friction loads, the films showed excellent wear resistance. Extrusion was believed to be the main wear mechanism of the films.