Graphene oxide versus graphite and chemically expanded graphite as solid lubricant in ultrahigh molecular weight polyethylene composites

Graphene oxide (GO), chemically expanded graphite (CEG) and graphite were evaluated as solid lubricant for ultrahigh molecular weight polyethylene composites. Under dry conditions, the addition of all solid lubricants increased the coefficient of friction by up to 38%. For the composites corrugated stick-slip features were observed which correlate with a decrease in matrix degree of crystallinity. GO had the lowest effect on the crystallisation, resulting in the lowest relative increase in friction coefficient of only 13%. Under water lubrication, GO, CEG and graphite were equally effective in reducing friction and wear. The highest friction for the neat matrix was found to be due to a transfer film, which was suppressed by the addition of the solid lubricants.