Surface wettability, tensile mechanical performance, and tribological behavior of polyimide/polytetrafluoroethylene blends enhanced with hydroxylated multiwalled carbon nanotubes at high relative humidity

Multiwalled carbon nanotubes were hydroxylated (MWCNTs-OH) by a strong acid mixture and then used as a reinforcement nanofiller in blends of polytetrafluoroethylene (PTFE) and polyimide (PI) to fabricate MWCNTs-OH/PTFE/PI nanocomposites. The influences of MWCNTs-OH additions on the surface wettability, tensile mechanical property, and tribological behaviors of MWCNTs-OH/PTFE/PI nanocomposites under different relative humidity were investigated. Test results indicate that the introduction of MWCNTs-OH can dramatically decrease the static water contact angles and increase the tensile strengths and elastic moduli of the PTFE/PI polymer blends. This is largely due to the existence of numerous hydrophilic functional groups on the surfaces of MWCNTs-OH and its ultrahigh mechanical characteristics. The relative humidity has a much weaker impact on the friction coefficients of the MWCNTs-OH/PTFE/PI nanocomposites than on the wear rates. Of all composites, the 0.8 wt% MWCNTs-OH/PTFE/PI nanocomposite possesses the lowest friction coefficient (0.11) and wear rate (2.97 x 10(-15) m(3)/(Nm)) at a high relative humidity of 90%. The conspicuous increase in wear resistance is attributable to the enhancement effect of MWCNTs-OH and the generation of homogeneous polymer self-lubricating tribofilms.

Automated summary

The hydroxylation of multiwalled carbon nanotubes and its incorporation into PTFE/PI nanocomposites significantly improves the mechanical properties and wear resistance. The 0.8 wt% MWCNTs-OH/PTFE/PI nanocomposite shows the lowest friction coefficient and wear rate at a high relative humidity of 90%, attributed to the enhancement effect of MWCNTs-OH and the formation of self-lubricating tribofilms.