Study On Mechanical Properties Of PI Composites Filled With Different Fillers

Polyimide (PI) refers to the main chain imide ring containing a polymer, which has excellent high temperature resistance, solvent resistance, radiation resistance, outstanding mechanical and dielectric properties, often widely used as high-performance thermoplastic composites in machinery, electronics, military, aerospace and other fields. However, due to the lower tensile strength, compressive strength of pure PI, which is not suitable to use alone as friction material, adding reinforcing fillers can significantly improve the mechanical properties of PI composites, PI friction and wear properties. The results were as follows:In this paper, carbon fiber (CF), silicon carbide fiber (SiC fiber), alumina fiber (Al2O3fiber), carbon powder (C powder), silicon carbide powder (SiC powder), alumina powder (Al2O3powder), solid lubricant (PTFE, MoS2and graphite) as the fillers, by surface treatment, the PI as matrix, prepared PI composites with different fillers by hot molding modified. Mechanical and friction wear properties of PI composites were investigated, cross-section of tensile, impact and friction wear surface were observed using scanning electron microscopy, the PI composites mechanical properties and friction wear performances which were improved by the fillers type, fillers content, fillers treatment, coupling agent and mixed modification were analysed, provided an effective theoretical basis for expanding the application of PI composites. The results were as follows:(1) The performances of PI composites filled with CF which were treated by coupling agent KH550, high temperature oxidation and ultrasound+coupling agent KH550combined (referred to as the ultrasonic compound treatment) were compared indicated thatThe mechanical and friction wear properties of PI composites, which were filled with CF treated by the ultrasonic compound treatment were better. The tensile cross-section microstructure showed a smooth and neat cross-section of pure PI, compact structure, the formation of radioactive silver in various patterns, showed a typical brittle fracture, untreated CF had poor adhesion with matrix, the section had hollows which were made by pulling out of the fiber, interfacial bonding of surface treated CF and PI matrix was good.(2) The properties of PI composites filled with three fiber (CF, Al2O3fiber, SiC fiber) were compared indicated that: The mechanical and friction wear properties of PI composites which were filled with SiC fiber were better, the wear mass and friction coefficient under the150N,200N and250N load were28%and78.7%,13.5%and71.9%,11%and73.1%of pure PI respectively. The worn surface of SiC fiber/PI composites had shallow furrows and adhesive wear was dominated. When the mass fraction of SiC fiber add to5%, the properties of SiC fiber/PI composites were better.(3) The comparison of the properties of PI composites which were blended with SiC fiber and solid lubricant (PTFE, MoS2and graphite) respectively indicated that:The mechanical properties of PI composites dropped when added the solid lubricant, because adding solid lubricant caused adhesion of SiC fiber and matrix deteriorated.But the wear mass and friction coefficient were greater improved, the friction and wear properties of PI composites filled with5%SiC fiber treated by ultrasound combined and10%graphite were better, the wear mass and friction coefficient under150N,200N and250N load were19.4%and57.8%,11.6%and63.8%,10.1%and61.5%of pure PI respectively.(4) The properties of PI composites filled with powder indicated that:The mechanical and friction wear properties of PI composites which were filled with SiC powder only was increased, but the extent of increase was lesser.The friction wear properties of PI composites were significantly improved through the synergy of SiC powder and solid lubricant, and the join of PTFE were better, the wear mass and friction coefficient under150N,200N and250N load were8.6%and41.7%,4.8%and38.4%,8.6%and40.2%of pure PI respectively;PI filled with different kinds of power and solid lubricant, compared the performances indicated that, the friction wear properties of PI composites filled with5%Al2O3powder and10%PTFE were better, the wear mass and friction coefficient under150N,200N and250N load were3.5%and38.3%,2.3%and34.4%,2.7%and40.9%of pure PI respectively.(5) The effect of coupling agent KH550content on the properties of CF/PI composites showed that, when the coupling agent KH550quality was3%of the fiber, the mechanical and friction wear properties of CF/PI composites were better.