Preparation And Tribological Properties Of Poly (Ether Ether Ketone) Composites Based On Graphite Nanosheets

Poly(ether ether ketone)(PEEK) is widely used in aerospace, energy, chemical,transportation, food processing, health care and other fields, due to the excellentcomprehensive performance and processibility. PEEK is a wear-resistant material andcan maintain good wear resistance in a wide temperature, load, speed and contactinterface roughness range. As a result, PEEK has a wide application prospects in thefields of friction materials. However, in its neat form, PEEK always exhibits a highfriction coefficient in dry sliding, hindering its utilization in tribological systems.Graphite nanosheets (GNS), as a kind of typical carbon material, have not only lowprice and good lubrication properties, but also high diameter-thick ratio(diameter/thickness ratio) and large specific surface area, which make it as analternative candidate in wear-resisting material. This thesis focuses on the preparationand performance of wear-resisting material based on PEEK and GNS.Poly(ether sulfone)(PES), which has matching overall performance with PEEK,was used to prepare GNS@PES through wrapping GNS. Then two series of composites(PEEK/GNS@PEEK and PES/GNS) were prepared via melt blending. Throughanalyzing and comparing the properties of the composites with different contents ofmodified and unmodified GNS filler, we found that the introduction of GNS fillerdramatically improved the mechanical properties, thermal stability, dimensionalstability and tribological properties of PEEK. The results could be ascribed to theformation of a PES interface layer between GNS and PEEK matrix. The interface layernot only improved the dispersibility of the GNS in PEEK matrix, but also enhanced theinterfacial force between PEEK and GNS. As a result, compared to PEEK/GNScomposites PEEK/GNS@PES composites exhibited better mechanical and wearproperties.For polymer-based friction materials, excellent mechanical properties couldimprove friction performance and broaden the application of the friction materials.Carbon fiber (CF) is a kind of reinforcing material with high performance, and it is usually used to enhance the strength, modulus, dimensional stability and tribologicalproperties of composites. Therefore, PEEK/GNS@PES/CF ternary composites wereperpared through introducing CF into the PEEK/GNS@PES composite. The resultsshowed that the introduction of carbon fibers could significantly improve themechanical properties and tribological properties of the composites.The special spiral-shaped configuration is beneficial for the intermolecularslippage among the polytetrafluoroethylene (PTFE) macromolecules. Furthermore, theabundant fluorine atoms endow PTFE with a more smooth shell. Therefore, a stableand uniform transfer film could be formed in frictional contact between the interfaces.As a result, PTFE has a very low friction coefficient and exhibits excellent tribologicalproperties during sliding. In order to further improve the tribological properties ofPEEK-based wear resistant material and broaden the applications, the content ofGNS@PES and CF were both fixed at10wt%. As a third packing, PTFE wasintroduced to prepare PEEK/GNS@PES/CF/PTFE quaternary composites. The resultsshowed that the friction coefficient of the quaternary composites is as low as0.254.After introduction of PTFE, the friction coefficient of the composites was significantlyreduced.