Lubrication properties of hydrogel-coated polyethylene head

Abstract

Frictional behavior of stainless steel cup against polyethylene head coated with dimethylacrylamide (DMAA) hydrogel was studied using a pendulum type friction tester. The friction coefficient of the pairs lubricated with Hyaluronic acid aq (HA) was as about 0.01, which is similar to that of living human hip or knee joint. The friction of the pair increased with loading time. When the coated head was immersed in the HA lubricant during an interval of repeated swing motions of the pendulum, the friction coefficient was above low value. The friction coefficient of the pair lubricated with a hydrophobic liquid (silicone oil) was as a high value of 0.4, close to the value without any lubricant. The friction coefficients of pairs lubricated with HA were not dependent on the load. The coefficients of friction lubricated with the biological factor (albumin, phospholipid) additive HA showed a little increase. Especially with albumin, the coefficient of friction increased with load. This behavior may be caused by the attachment albumin to hydrophilic high molecular chain by chemical adsorption. From these experimental observations, it is surmised that the low friction shown in coated PE head is caused by the formation of highly viscous zone through hydration of DMAA at the solid/liquid interface.