Polytetrafluoroethylene (PTFE) exhibits desirable tribological characteristics, including low friction, high melting temperature and chemical inertness. Based on these characteristics, PTFE is a frequently used solid lubricant both as a filler and matrix material. Without a filler, however, PTFE suffers from a relatively high wear rate, generally precluding its use in frictional applications, including use as a bearing material.
As a matrix material, PTFE has been successfully filled with various nanoparticles, including alumina, zinca, and carbon nanotubes. Regarding alumina filling, Sawyer et al. [Sawyer, W. G., Freudenburg, K. D., Bhimaraj, P., and Schadler, L. S., (2003), “A Study on the Friction and Wear of Ptfe Filled with Alumina Nanoparticles,” Wear, 254, pp. 573-580] discloses 38 nm substantially spherical shaped Al2O3 filler particles for improving the wear performance of PTFE. The wear resistance of this nanocomposite was reported to increase monotonically with filler wt %, eventually being 600 times more wear resistant than unfilled PTFE at a loading of 20 wt. % Al2O3. Although the wear performance provided by PTFE/alumina nanocomposites disclosed by Sawyer et al. represents a major improvement over PTFE, the high filler percentage required to reach the desired wear level significantly raises the cost of the nanocomposite. In addition, for certain applications wear rates lower than 600 times better than PTFE are desirable and may even be required. Accordingly, a PTFE nanocomposite is needed which provides improved wear resistance, while at the same time requiring a lower filler percentage as compared to the PTFE nanocomposites disclosed by Sawyer et al.
USPTO Backgrounds
USPTO Backgrounds