Study On The Tribological Properties Of PTFE-Based Composites Filled With Inorganic Fillers

Polytetrafluoroethylene(PTFE), a kind of self-lubricating material with good comprehensive performances such as very low frictional coefficient, good thermal stability and anti-crrosion, has been widely used in verious engineering fields. However, pure PTFE is not suitable for the wear resistance applications because of its bad mechanical performance, high linear expansion coefficient and low thermal conductivity. Usually the performances of PTFE can be improved by adding fillers. In this thesis, the tribological properties and wear mechanisms of a series of PTFE-based composites were experimentally and therotically studied, which were filled with copper powders(6-6-3 and 8-3), glass fibers,graphite,carbon fiber and carbon nanotubes in different amounts and different sizes. In addition, the thermal conductivity of different composites was also measured, and the influence of thermal properties of the composites on the tribological properties was investigated. Moreover, some useful results were obtained.The influences of the type, amount and diameter of copper powders on the tribological properties of PTFE-based composites were studied. The studied results of the composites with different amounts of 6-6-3 or 8-3 copper powders (also including 5% glass fiber and 5% graphite) showed that the best copper powder amount is 15% or 30% to get the best friction property for 6-6-3 or 8-3, respectively. The wear of the composites decreased with the increase of copper powder amount, and the composite filled with 8-3 copper powder has a better performance. The tribological properties of the composites with different size 6-6-3 or 8-3 copper powders revealed that smaller copper particles has adverse effects not only on the improvement of frictional performances of the composites, but also on the increase of the anti-wear of the composites.The influences of the amount of carbon fiber and carbon nanotube on the tribological properties of PTFE-based composites were also investigated. The experimental results about the composites with different amounts of carbon fiber and carbon nanotube (also including 5% glass fiber and 30% 8-3 copper powder) showed that the frictional coefficient of the composites decreased gradually with the increase of the amount of carbon fiber, but the increase of the amount of carbon nanotube exhibited a adverse effect. The thermal conductivity the composites were measured and analyzed. The results showed that the filling of 6-6-3 copper powder, 8-3 copper powder, carbon fiber and carbon nanotube can increase the thermal conductivity of the composites in different extent, and the increase of the thermal conductivity of the composites has beneficial effect on the improvement of the anti-wear performance of the PTFE-based composites.