The tribological behaviour of glass filled polytetrafluoroethylene(PTFE) under dry and water lubrication
Master Thesis
2003
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University of Cape Town
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Abstract
This study was aimed at establishing the tribological behaViour of 25 % wt glass fibre filled polytetrafluoroethylene (PTFE) under dry sliding conditions. The experimental work was extended to compare and include its wear behaviour with other fillers such as bronze, carbon and graphite and to conduct tests under under water lubrication. Polyester-based materials, Vesconite and Vesconite Hilube, were used in this study for comparison purposes as well. The worn polymer pin surfaces and the counterfaces were studied by means of optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EOS), x-ray photoelectron spectroscopy (XPS) and surface profilometry. X-ray diffraction (XRO) and differential scanning calorimetry (OSC) were employed to study the changes in crystallinity and morphology of PTFE composite wear surfaces during the sliding process. The effect of the different forms of glass, viz. glass fibres, glass beads (hollow and solid beads) and glass flakes on the friction and wear behaviour of PTFE was investigated. The effect of additions of small amounts of additive such as molybdenum disulphide, MoSâ‚‚ and pigments on the wear rate of glass fibre filled PTFE was also investigated. The results show that the addition of glass fillers to PTFE reduce the wear of PTFE by three orders magnitude while keeping the coefficient of friction more or less unchanged. The reduction in wear upon addition of the glass to PTFE was attributed to the formation of a coherent and adherent transfer film to the counterface during the sliding process. The transfer film formed by unfilled PTFE was quite patchy and non-adherent to the metal counterfaces.
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Klaas, N. 2003. The tribological behaviour of glass filled polytetrafluoroethylene(PTFE) under dry and water lubrication. University of Cape Town.