Effects of polyimide/silica and polyimide/pores fillers on the morphology, thermal, mechanical, and tribological properties of polytetrafluoroethylene composites

Abstract

The effects of polyimide with silica (SiO2-PI) and pores (porous PI) on the morphology, thermal, mechanical, and tribological properties of polytetrafluoroethylene (PTFE) composites were investigated. SiO2-PI and porous PI fillers decrease the compactness of PTFE matrices within PTFE/SiO2-PI composites and PTFE/porous-PI composites. In addition, SiO2-PI fillers improve the interfacial bonding between PI fillers and PTFE matrices, which is opposite to the detrimental effect of porous PI fillers. Thermal and mechanical properties of PTFE composites were deteriorated apparently. The friction coefficients of PTFE/SiO2-PI and PTFE/porous-PI composites are 9.5% and 8.5% lower than that of PTFE/PI, respectively. The wear resistance of PTFE/SiO2-PI and PTFE/porous-PI composites is enhanced by 77.8% and 70.1%, respectively. Scanning electron microscopy (SEM) of worn surface indicates that SiO2-PI and porous PI fillers protect PTFE matrices from counterpart ball, which inhibits the plastic flow of PTFE matrices effectively. In addition, the uneven worn surface decreases the contact area between PTFE composites and counterpart ball. Compared with SiO2-PI fillers, the extension of porous PI fillers in friction process increases the contact area between PTFE composites and counterpart, which induces the relatively poor tribological performance of PTFE/porous-PI. Furthermore, SiO2-PI and porous PI fillers contribute to the formation of smooth and uniform transfer films, which improve the tribological performance of PTFE composites effectively. In addition, compared with adding SiO2-PI into PTFE, the addition of SiO2 nanoparticles into PTFE/PI induces the rough and uniform transfer films, which is bad for tribological performance of PTFE/PI/SiO2 composites.