Desenvolvimento de compósitos tribologicamente eficazes

Abstract

The storage scheelite tailings in the open air as a result of Brejuí mine exploration, located near Currais Novos, Rio Grande do Norte, Brazil, between 1960 and 2015, a strong environmental passive. The polymer polytetrafluoroethylene (PTFE) outstands in sliding systems and significantly reduces maintenance costs, due to its excellent mechanical properties, such as low friction coefficient (0,01<  <0,10) and yield limit to the order of 10MPa. However, it has high wear rates (10-13 m2/N) and for arousing scientific and technological interests at petrochemical and aerospace industry, in the form of solid lubricants, the target was to develop polymeric composites with a PTFE matrix using tailings of scheelite as charge, enabling also environmental remediation processes. The tailing of Sheelite was characterized in acquired conditions, through XRD, XRF, SEM, EDS, granulometry by screening and by laser, recording traces of tungsten and strategic metals equally important. The PTFE was analyzed by TG, DSC, SEM, XRD, XRF. To the composites development, powders of PTFE and tailings of sheelite were mechanically mixed, previously prepared and weighed. To hot compression molding, a designed cylindrical steel mould was coupled with a resistor and placed in a hydraulic press. The composite’s tribological performance was evaluated from roughness, hardness, wettability, impact absorption, sclerometry, pin on disc, and morphological analysis. The results show that the variation in the tailing of scheelite concentration influences the results of roughness, hardness and impact absorption. Wet composites with saline and distilled water were characterized as hydrophobic, and the ones wet with paraffenic and naphtenic oil, they acted oleophilic. Correlating the results of tribological tests and costs, it was found that the composition of 20% mineral filler showed better planeness, low specific deformation energy consumption (<0,30J/mm³), the lowest mass loss (8x10-4g) and trail shipwreck (<0,4μm/km).