MXene as a multi-functional 2D reinforcement in self-lubricating PEEK-based composites

MXene has been widely evaluated as a 2D reinforcement in polymer-based composites due to its large specific surface area, abundant surface chemical bonding sites, and robust layer bonding. However, when considering the polymer-based solid lubricant, MXene not only displays crucial roles in the aspects of mechanical properties but also contributes to the frictional processes. Particularly, unlike traditional van der Waals crystals (graphite, MoS₂, etc.), MXene nanoflakes have much stronger interlayer interactions. Therefore, the detailed mechanism of MXene on self-lubricating and anti-wear performances must be clarified. Herein, by introducing Ti₃C₂T_x MXene in a poly(ether-ether-ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE) composites, a series of composites with different component ratios are prepared, and their self-lubricating performance is evaluated under dry-sliding conditions. The positive role of Ti₃C₂T_x nanoflakes on tribofilm formation is probed, which includes improving the interfacial bonding between the polymer grains, enhancing the adhesion of PTFE chains on the counterpart ZrO₂ balls, and dispersing the stress on counter surfaces during friction. Eventually, MXene-reinforced PEEK-based composites display both a lower coefficient of friction and a lower wear rate than the previously reported PEEK-PTFE composites, which exhibit comparable self-lubricating performance to pure PTFE and a tensile strength of over 100 MPa. The current studies illuminate the crucial roles of MXene in PEEK-based solid lubricants and pave the way for theconstruction of novel solid lubricants as well.