Tribological Properties And Mechanism Of PTFE/PI Composites Controlling The Distribution Regions Of Nanoparticles

Self-lubricating bearing is the key factor affecting the performance of aviation self-lubricating bearings.Polymer self-lubricating material is used in aviation self-lubricating joint bearings because of their light weight and self lubricating performance.However,the wear performance needs to be improved in order to promote the wide application of self-lubricaing bearings.Nano-modification is one of the effective methods to improve the tribological properties of polymer self-lubricating materials.In this paper,PTFE composites were prepared by incorporating SiO₂ nanoparticles or Cu nanoparticles in different regions of PTFE/PI blends.The effects of nanoparticles dispersed in different regions on the tribological properties of PTFE composites were investigated.And the microscopic properties,macroscopic properties,worn morphology and transfer films of PTFE composites were studied systematically.Then the relationship between wear resistance,microscopic and macroscopic performance were analysized.At last,the effects of nanoparticles located in different regions on the microscopic behavior of PTFE composites were studied using molecular dynamic simulation to explore the relationship between microscopic performance and tribological behavior.PI-SiO₂ composites were prepared using an in-situ polymerization.High content（20wt%）of SiO₂ nanoparticles were dispersed homogeneously in PI matrices.Thermal resistance,mechanical and tribological performance of PI composites was improved effectively by uniformly dispersed SiO₂ nanoparticles.The effects of SiO₂ nanoparticles dispersed in different regions on the friction and wear behavior of PTFE composites were studied.PTFE composites exhibit the best friction and wear properties when SiO₂ nanoparticles are dispersed in PI.Compared with this,PTFE composites exhibit relatively poor friction and wear resistance when SiO₂nanoparticles are dispersed in PTFE and PTFE/PI interface simultaneously.The effects of SiO₂ nanoparticles on the worn morphology and wear resistance of PTFE composites are corresponding to the influence of SiO₂ nanoparticles on the microscopic structure and microscopic performance.The dispersion uniformity and microscopic mechanical performance of PI phases and the interfacial performance between PTFE and PI are improved when SiO₂ nanoparticles dispersed in PI phases.As a result,the plastic flow of PTFE resin is inhibited effectively,which improves the wear resistance of PTFE composites.Compared with this,the dispersion uniformity and microscopic mechanical performance of PI phases and the interfacial performance between PTFE and PI are relatively poor when SiO₂ nanoparticles are dispersed in PTFE and PTFE/PI interface simultaneously.As a result,the plastic flow of PTFE resin is severe.Additionally,the effect of Cu nanoparticles dispersed in different regions on the tribological properties and mechanism of PTFE composites.The results indicate that Cu nanoparticles dispersed in PI phases improve the friction and wear performance of PTFE composites.However,the tribological performance of PTFE composites is relatively poor when Cu nanoparticles are dispersed in PTFE and PTFE/PI interface simultaneously.The effects of Cu nanoparticles on the worn morphology and wear resistance of PTFE composites are corresponding to the influence of Cu nanoparticles on the microscopic structure and microscopic performance.Compared with Cu nanoparticles dispersed in PTFE and PTFE/PI interface simultaneously,Cu nanoparticles dispersed in PI phases improve the dispersion uniformity of PI phases and the interfacial performance between PTFE and PI.As a result,the plastic flow of PTFE resin is inhibited effectively,which contributes to the improvement of wear resistance of PTFE composites.Molecular dynamic simulation was employed to investigate the effects of nanoparticles dispersed in different regions of PTFE composites on the microscopic structure and microscopic performance at molecular level.The results indicate that the enhancement effects of nanoparticles on the intermolecular interaction of PTFE molecules and the compatibility between PTFE and PI contributes to the improvement of wear resistance of PTFE composites.