Interrelated Effects of Temperature and Environment on Wear and Tribochemistry of an Ultralow Wear PTFE Composite

Khare, H. S.; Moore, Axel C.; Haidar, Diana R.; Gong, Liang; Ye, J.; Rabolt, John F.; Burris, David L.

doi:10.1021/acs.jpcc.5b00947

Cited by 82 publications

(70 citation statements)

References 47 publications

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“…Obviously such additives should be selected which bear the same functional groups evolved according to above schemes, which may enter in reaction with them, or which have possible ligands for the supposed complex formation. The latter aspect seems to be confirmed by the ultralow wear results measured for PTFE with alumina and silicate type nanofillers [6][7][12][13][14][15]. Suitable functional groups for complexing can be produced, however, also on carbonaceous nanofillers, such as CNT and graphene derivatives.…”

Section: Introductionmentioning

confidence: 72%

“Ultralow” sliding wear polytetrafluoro ethylene nanocomposites with functionalized graphene

Padenko

Rooyen

Wetzel

et al. 2016

Journal of Reinforced Plastics and Composites

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Abstract:The dry friction and sliding wear behavior of sintered PTFE containing various amounts of functionalized graphene (GR) were studied in this work. GR was incorporated in 0, 0.25, 0.75, 1, 2 and 4 vol%, respectively. Sliding wear tests were performed in ring(metal)-on-plate(PTFE) (ROP) test rig under ambient temperature setting 1 m/s sliding speed and 1 MPa contact pressure. The dynamic coefficient of friction (COF) and specific wear rate (ws) data were determined. Very low COFs (0.12-0.14) were measured for PTFE containing 2 or 4 vol% GR which was attributed to the formation of a tribofilm on the countersurface. ws went through a maximum (peaked at doubling that of the unmodified PTFE at about 0.75 vol% GR) as a function of GR content. Ultralow ws data in the range of 10 -6 mm 3 /(N.m) were measured for the PTFE nanocomposites with 2 and 4 vol% GR. This was reasoned by the formation of a robust tribofilm, the development of which was followed by scanning electron microscopy (SEM) by inspecting the worn surface of PTFE nanocomposites and that of the steel ring of the ROP test rig. Fourier transform infrared spectroscopic results confirmed the formation of carboxyl groups in the tribofilm. They were 2 supposed to react with the functional groups of GR and to create complexes with the metal countersurface ensuring the tribofilm with high adhesion and cohesion strengths.

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Section: Introductionmentioning

confidence: 72%

“Ultralow” sliding wear polytetrafluoro ethylene nanocomposites with functionalized graphene

Padenko

Rooyen

Wetzel

et al. 2016

Journal of Reinforced Plastics and Composites

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show abstract

“…In addition to producing thinner and more uniform transfer films, low-wear alumina-PTFE transfer films are obviously discolored [13,18,20,[23][24][25][26][27]29,31,32,[37][38][39], which suggests chemical reactions had taken place and possibly enhanced adhesion of the transfer film. In 2013, Ye and Burris used optical microscopy to determine the degree to which transfer films persist during sliding [20].…”

Section: The Effects Of Filler Characteristics On Transfer Films and mentioning

confidence: 99%

“…Harris et al [27] found evidence showing that PTFE chain ends not only chelate to the steel surface under the transfer film, but also to the surface of the alumina filler particles. Thus, tribochemistry in this system appears to stabilize the transfer film and the sliding surface of the solid lubricant, thus compartmentalizing damage and reducing wear [39]. As a group with unprecedented expertise in tribology and fluoropolymer chemistry, Harris et al [27] proposed a likely tribochemistry-based wear reduction mechanism in PTFE-related systems with the following essential steps: (1) PTFE chains break during sliding and form perfluoroalkyl radicals at new chain ends; (2) the perfluoroalkyl radicals react with atmospheric oxygen to form acyl fluoride end groups; (3) the acyl fluoride end groups hydrolyze in ambient humidity to form carboxylic acids; and (4) the perfluorinated carboxylic acids chelate to metals (Fe in the steel counterface and Al in the alumina fillers), thus stabilizing the transfer film and near surface of the pin.…”

Section: Chemistry Of the Transfer Filmmentioning

confidence: 99%

A Review of Transfer Films and Their Role in Ultra-Low-Wear Sliding of Polymers

Burris

Xie

2016

Lubricants

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Abstract:In dry sliding conditions, polytetrafluoroethylene (PTFE) composites can form thin, uniform, and protective transfer films on hard, metallic counterfaces that may play a significant role in friction and wear control. Qualitative characterizations of transfer film morphology, composition, and adhesion to the counterface suggest they are all good predictors of friction and, particularly, wear performance. However, a lack of quantitative transfer film characterization methods and uncertainty regarding specific mechanisms of friction and wear control make definitive conclusions about causal relationships between transfer film and tribological properties difficult. This paper reviews the state of the art in the solid lubricant transfer film literature and highlights recent advances in quantitative characterization thereof.

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“…Polymer‐based composites have been widely used in numerous triboengineering applications and show high tribological performances under dry sliding conditions . For numerous applications, the addition of combined reinforcing fillers and solid lubricants, e.g., short carbon fibers (SCFs) and MoS 2 , provides an efficient solution for simultaneously reducing the friction and wear .…”

Section: Introductionmentioning

confidence: 99%

Ultralow Friction and Wear of Polymer Composites under Extreme Unlubricated Sliding Conditions

Zhang

Chang

et al. 2017

Adv Materials Inter

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Dependence of the tribological behaviors of polyimide‐ and polyetheretherketone‐based composites on pv (pressure × speed) factors is investigated in air ambience. It is demonstrated that the hybrid composites filled with nanosilica/carbon fibers/graphite exhibit ultralow friction and wear under extreme conditions. In particular, the friction coefficients of the hybrid nanocomposites at 40 MPa m s−1 are in the range of 0.03–0.04, which are even lower than those obtained with poly alpha olefin lubrication. Moreover, the friction coefficients are lower than those of carbon fibers reinforced polymer composites ever reported in literatures. In order to reveal the underlying mechanisms of ultralow friction and wear, tribochemistry and tribofilms' nanostructures are comprehensively analyzed. It is identified that chelation of polymeric molecular radicals with steel counterface occurs enhancing tribofilm's bonding strength. Striking orientation of the molecules of remnant polymer in tribofilm is indicative that the film exhibits an easy‐to‐shear characteristic under extreme pv conditions. Nanosilica released onto sliding interface and iron oxide particles abraded from the counterface are thereafter tribosintered into a compact layer, which accounts for the high load‐carrying capability of the tribofilm.

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Interrelated Effects of Temperature and Environment on Wear and Tribochemistry of an Ultralow Wear PTFE Composite

Cited by 82 publications

References 47 publications

“Ultralow” sliding wear polytetrafluoro ethylene nanocomposites with functionalized graphene

“Ultralow” sliding wear polytetrafluoro ethylene nanocomposites with functionalized graphene

A Review of Transfer Films and Their Role in Ultra-Low-Wear Sliding of Polymers

Ultralow Friction and Wear of Polymer Composites under Extreme Unlubricated Sliding Conditions

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