Improved wear resistance of nanotube- and other carbon-filled PTFE composites

Microfillers have long been shown to reduce the wear rate of PTFE by up to two orders of magnitude. One hypothesized mechanism resulting in this wear reduction is the interruption of subsurface crack formation, which prevents the formation of delamination debris. Recent studies into nanofillers have shown some promising results, but only for very few types of fillers. Notably, alpha-phase alumina and activated nanocarbon have been shown to impart exceptional wear resistance to PTFE composites, outpacing that provided by the same materials on the microscale. As described here, carboxyl-functionalized carbon nanotubes and mesoporous nanocarbon have both been additionally identified as effective nanoscale fillers, with composites approaching wear rates as low as 10−7 mm3/Nm. It is believed that the functionalized carbon nanotube fillers presented here may combine microscale mechanisms, such as subsurface arrest of crack propagation, with a uniquely nanoscale mechanism as held by the mesoporous nanocarbon, and that the effectiveness of such mechanisms increases with increased filler content.