Avaliação tribológica de compósitos de PTFE em ensaios tipo pino sobre disco

Abstract

Recent studies in the laboratory of Surface and Contact Analysis in the UTFPR evaluated the tribological properties of pure polytetrafluoroethylene (PTFE) versus stainless steel, without lubrication, on pin-on-disc tests. On the continuation of this project, the changes on tribological properties were demonstrated, when particles of graphite or bronze are added to this polymer. Further analysis included: evaluation of surface topography before and after wear using SEM micrographs and white-light interferometer measurements; determination of the coefcient of friction as a function of normal force; determination of wear rate as a function of loading level; and the molecular variation on polymer chains, from the FTIR analysis. The results were satisfactory. Signs of transfer flm wear mechanisms were detected, as well as abrasion mechanisms in a lesser degree. Coefcient of friction was found to be smaller in the graphite-flled composite. Bronze did not affect the coefcient of friction, either positively or negatively, as bronze-flled PTFE composite showed statistically equal friction results compared to pure PTFE. Wear rates on composites were four to fve times lower than pure PTFE rates, proving the effectiveness of fllers. Graphite and bronze contributions on PTFE wear resistance are similar, as the effects of both on wear are statistically equivalent. Lastly, molecular alterations were not found on the surface of pins.