Thermal fluctuations at PTFE friction and transfer

Pleskachevsky, Yu. M.; Smurugov, V. A.

doi:10.1016/s0043-1648(97)00034-3

Cited by 33 publications

(18 citation statements)

References 2 publications

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“…The background temperature inside the glove box was held constant at 296 ± 1 K. The dew points of the 2% and 6% relative humidity experiments were calculated to be 243 K and 255 K, respectively. Uchiyama [12] (g) Pleskachevsky and Smurugov [14]. This dataset suggests that the friction of PTFE is a thermally activated process with an activation energy near 5 kJ/mol over the temperature range from 200 to 425 K. The results collected in the current study are connected by lines.…”

Section: Methodssupporting

confidence: 60%

“…It is wellknown that PTFE films transfer and adhere strongly to the counterface, and a modern hypothesis is that both friction and wear of PTFE are dominated by the interactions of PTFE chains sliding past one another at weak self-mated interfaces, often within transfer films [9][10][11][12][13][14][15]. A recent paper by McCook et al [4] found that friction of PTFE matrix composites continued to increase in the cryogenic regime down to 200 K, and the notion of a thermally activated friction coefficient for PTFE was proposed (analysis of an activation energy gave E a = 3.7 kJ/mol).…”

Section: Introductionmentioning

confidence: 99%

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Macroscopic Evidence of Thermally Activated Friction with Polytetrafluoroethylene

2007

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Under macroscopic pin-on-disk testing the sliding friction coefficient of Polytetrafluoroethylene (PTFE) was investigated over a temperature range of approximately 200-400 K. This study examines the nature of the temperature dependence by testing PTFE pins at varying temperature and humidity on a linear reciprocating pin-on-disk tribometer. The friction coefficient increased monotonically with decreasing temperature from l = 0.075to l = 0.210 in a manner consistent with thermal activation; it deviated from this trend only during phase and glass transitions in the PTFE and temperatures below the frost-points for the respective environments.

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Section: Methodssupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Macroscopic Evidence of Thermally Activated Friction with Polytetrafluoroethylene

2007

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“…Recent constant environment macroscale studies of various solid lubricants [4][5][6][7], and atomic-scale studies with terraces of graphite [8] show consistent trends of increased friction with decreased temperature, and the notion of thermally activated friction has been proposed [4,8,9]. Variable temperature experiments conducted on beds of aligned carbon nanotubes [10] and various high temperature polymer studies [11][12][13][14][15][16] have also demonstrated behavior that is well fit by an activated process at the macroscale. Burton et al [17] found inconclusive trends during tilted sled experiments with sapphire, PTFE, and other materials over a range of 4-400 K under dry sliding in vacuum but notes that ''…we believe that the effects of wear overwhelm any possible temperature dependent friction mechanisms.''…”

Section: Introductionmentioning

confidence: 82%

A Possible Link Between Macroscopic Wear and Temperature Dependent Friction Behaviors of MoS2 Coatings

et al. 2008

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Studies to explore the nature of friction, and in particular thermally activated friction in macroscopic tribology, have lead to a series of experiments on thin coatings of molybdenum disulfide. Coatings of predominately molybdenum disulfide were selected for these experiments; five different coatings were used: MoS 2 /Ni, . The temperatures were varied over a range from -80°C to 180°C. The friction coefficients tended to increase with decreasing temperature. Activation energies were estimated to be between 2 and 10 kJ/mol from data fitting with an Arrhenius function. Subsequent room temperature wear rate measurements of these films under dry nitrogen conditions at ambient temperature demonstrated that the steady-state wear behavior of these coatings varied dramatically over a range of K = 7 9 10 -6 to 2 9 10 -8 mm 3 /(Nm). It was further shown that an inverse relationship between wear rate and the sensitivity of friction coefficient with temperature exists. The highest wearrate coatings showed nearly athermal friction behavior, while the most wear resistant coatings showed thermally activated behavior. Finally, it is hypothesized that thermally activated behavior in macroscopic tribology is reserved for systems with stable interfaces and ultra-low wear, and athermal behavior is characteristic to systems experiencing gross wear.

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“…However, efficient lubrication is only attained in a self-regulating temperature range, where lamellar transfer layers provide optimum bearing capacity and rheological properties. Pleskachevsky et al [41] showed that PTFE has lowest friction at around 120°C. The thermally controlled sliding of pure PTFE agrees very well with the frictional tendencies of CF-TP-PTFE.…”

Section: Effect Of Thermal Heating and Pv-conditionsmentioning

confidence: 99%

Influence of Internal Lubricants (PTFE and Silicon Oil) in Short Carbon Fibre-Reinforced Polyimide Composites on Performance Properties

2009

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Short carbon fibre-reinforced thermoplastic polyimides (30 wt%) often show high and unstable coefficients of friction. In this study, the effects of internal lubrication by polytetrafluoroethylene (PTFE) (15 wt%) or silicon oil (15 wt%) have been investigated using a reciprocating cylinder-on-plate test under 50-100 N normal loads and 0.3-1.2 m/s sliding velocities. The sliding mechanisms are discussed by considering mechanical and thermochemical modifications. The PTFE additives provide lowest coefficients of friction completely stabilising after a transition from mechanically into thermally controlled sliding at 120°C. The sliding mechanisms and homogeneous transfer films are mainly controlled by plasticisation rather than easy-shear of its lamellar structure that is hindered by fibre reinforcement. Thermoplastic lubricants decrease the mechanical strength and therefore cause deformation and highest wear rates under 200 N. Internal oil lubricants do not reduce coefficients of friction at mild to intermediate normal loads and sliding velocities, while they become most efficient at severe sliding conditions, augmenting the pv-limit. While coefficients of friction match uniquely to the pv-conditions, the wear rates are mainly influenced by the load level: the lowest wear rates are provided by PTFE at low to intermediate pv-conditions and by oil lubricants under high normal loads.

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Thermal fluctuations at PTFE friction and transfer

Cited by 33 publications

References 2 publications

Macroscopic Evidence of Thermally Activated Friction with Polytetrafluoroethylene

Macroscopic Evidence of Thermally Activated Friction with Polytetrafluoroethylene

A Possible Link Between Macroscopic Wear and Temperature Dependent Friction Behaviors of MoS2 Coatings

Influence of Internal Lubricants (PTFE and Silicon Oil) in Short Carbon Fibre-Reinforced Polyimide Composites on Performance Properties

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