Mechanical and tribological behavior of polytetrafluoroethylene composites reinforced by carbon nanotubes and poly-p-oxybenzoate

Effects of microscale poly- p-oxybenzoate (trade name Ekonol), nanoscale carbon nanotubes (CNTs) and multiscale fillers on the mechanical, creep and tribological properties of polytetrafluoroethylene (PTFE) are studied. Results reveal that the multiscale PTFE composite with 20 wt% Ekonol and 1 wt% CNTs has the highest tensile strength and modulus as well as relatively modest elongation at break compared to pure PTFE, micro and nanoscale PTFE composites. In addition, the combination of Ekonol and CNT fillers leads to a significant improvement in creep resistance of PTFE composites. Scanning electron microscopic observation of tensile fracture surfaces indicates that for multiscale composite, the surfaces of Ekonol particles are wrapped by individual CNTs and the bridge of CNTs between Ekonol particles is formed. Also, the combination of Ekonol and CNT fillers slightly increases the friction coefficient of multiscale composite but greatly decreases the wear rate by approximately four orders of magnitude compared with pure PTFE. Scanning electron microscopic observation of the worn surfaces shows that the wear surface of the multiscale composite is very smooth. Therefore, the wear resistance significantly improved. The synergetic role of multiscale fillers is expected to open up new opportunities to formulate high-performance PTFE composites.