Study On Frictional Properties Of CNT Modified PEEK/PTFE Composites

Polytetrafluoroethylene（PTFE）is an important application material in industries such as petrochemicals,machinery,and chemistry due to its self-lubricating,impermeable,and corrosion-resistant properties.Especially PTFE has extremely low friction coefficient and is widely used in the field of dynamic sealing.Especially PTFE has extremely low friction coefficient and is widely used in the field of dynamic sealing.Polyetheretherketone（PEEK）has good corrosion resistance,lightweight,and low cost,and is often used in combination with PTFE.To further enhance the frictional performance of polymers and meet the increasing demands of dynamic sealing,a modification study was conducted on PTFE widely used in polymers,utilizing the unique structure and excellent physical and mechanical properties of carbon nanotube（CNT）,through a method that combined PEEK and CNT filling.The molecular dynamics simulation method and the experimental research method of multi scale analysis were used to reveal the structural characteristics and strengthening mechanism of the polymer.PTFE was used as the matrix,and PEEK,CNT,and functionalized CNT were respectively filled in.Molecular dynamics simulation was used to analyze and reveal the reinforcement differences and action mechanisms of different fillers on the matrix in terms of friction performance from a microscopic perspective.Furthermore,the enhancement mechanism of the friction surface of PEEK/PTFE composite material matrix by CNT with different functional groups was explored.Based on the results of molecular dynamics simulation analysis,CNT/PEEK/PTFE composite materials were prepared,and their mechanical and frictional properties were experimentally characterized.The specific research content is as follows:（1）Material Studio（MS）software was used to construct models of PTFE composite with0%,5%,10%,15%and 20%PEEK.The mechanical and tribological properties of the composites were calculated,and parameters such as free volume fraction and interfacial interaction energy were compared to explore the reinforcing mechanism of PEEK on the PTFE matrix.The simulation results showed that the 10%PEEK/PTFE composite exhibited good mechanical and tribological properties.When the PEEK content exceeded 20%,stress concentration occurred and the properties of the composite significantly decreased.（2）The mechanical and frictional properties of CNT/PEEK/PTFE composite materials were analyzed by adding 1%,3%,and 5%CNT to the 10%PEEK/PTFE composite.The temperature and total potential energy parameters of the friction process were simulated to explore the enhancement differences of CNT on the PEEK/PTFE matrix.In the simulation results,the good mechanical and tribological properties were exhibited by 3%CNT/10%PEEK/PTFE.（3）Surface modification of CNT was carried out to improve the agglomeration tendency caused by van der Waals interaction of carbon nanomaterials,in order to fully exploit the filling enhancement effect.Models of amino-functionalized CNT（CNT-NH₂）,ester-functionalized CNT（CNT-COOCH₃）,and carboxylic-functionalized CNT（CNT-COOH）were constructed to enhance 10%PEEK/PTFE composite materials.The mechanical and tribological properties of the functionalized CNT/PEEK/PTFE composite materials were calculated and compared,while analyzing parameters such as temperature and total potential energy during frictional processes,as well as dipole autocorrelation functions to investigate the difference in enhancement of the functionalized CNT to the matrix.The hydrogen bonding and van der Waals interactions between the functional groups and the matrix,as well as the mean square displacement between the molecular chains were calculated to reveal the reinforcement mechanism of the functional groups on the matrix properties.（4）Based on the conclusions of molecular dynamics studies,pure PTFE materials,10%PEEK/PTFE,3%CNT/10%PEEK/PTFE,and 3%COOH-CNT/10%PEEK/PTFE were prepared by the processes,such as mechanical mixing,high-pressure pressing,and high-temperature sintering.The mechanical properties（tensile and compression testing）,friction and wear properties,and wear morphology（SEM）of these materials were analyzed and observed.Through the two-way characterization of experiments and molecular dynamics,the friction and wear mechanisms of CNT/PEEK/PTFE composite materials were studied,theoretical basis was provided for the development and application of PTFE-based composite materials.