Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

Uçar, Ahmet; Çopuroğlu, Mehmet; Baykara, Mehmet Z.; Arıkan, Orhan; Süzer, Şefik

doi:10.1063/1.4898384

Cited by 6 publications

(5 citation statements)

References 32 publications

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“…44 This observation implied that aligned PTFE chains were transferred to steel after a single sliding pass, which agrees with surface plasmon resonance results from Krick et al 45 and XPS results from Ucar. 46 Because of its extremely high molecular weight (∼ tens millions g/mol 47 ), granular PTFE is unlikely to transfer an entire chain to the metal surface, thus C−C backbone bond scission is likely involved. A simple mathematical argument can be made to support the bond breaking and transfer of PTFE chains in the first cycle of sliding.…”

Section: Resultsmentioning

confidence: 99%

PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films

Harris¹,

Pitenis²,

Sawyer³

et al. 2015

Macromolecules

250

185

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The wear and friction behavior of ultralow wear polytetrafluoroethylene (PTFE)/α-alumina composites first described by Burris and Sawyer in 2006 has been heavily studied, but the mechanisms responsible for the 4 orders of magnitude improvement in wear over unfilled PTFE are still not fully understood. It has been shown that the formation of a polymeric transfer film is crucial to achieving ultralow wear on a metal countersurface. However, the detailed chemical mechanism of transfer film formation and its role in the exceptional wear performance has yet to be described. There has been much debate about the role of chemical interactions between the PTFE, the filler, and the metal countersurface, and some researchers have even concluded that chemical changes are not an important part of the ultralow wear mechanism in these materials. Here, a "stripe" test allowed detailed spectroscopic studies of PTFE/α-alumina transfer films in various stages of development, which led to a proposed mechanism which accounts for the creation of chemically distinct films formed on both surfaces of the wear couple. PTFE chains are broken during sliding and undergo a series of reactions to produce carboxylate chain ends, which have been shown to chelate to both the metal surface and to the surface of the alumina filler particles. These tribochemical reactions form a robust polymer-on-polymer system that protects the steel countersurface and is able to withstand hundreds of thousands of cycles of sliding with almost no wear of the polymer composite after the initial run-in period. The mechanical scission of carbon−carbon bonds in the backbone of PTFE under conditions of sliding contact is supported mathematically using the Hamaker model for van der Waals interactions between polymer fibrils and the countersurface. The necessity for ambient moisture and oxygen is explained, and model experiments using small molecules confirm the reactions in the proposed mechanism.

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Section: Resultsmentioning

confidence: 99%

PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films

Harris¹,

Pitenis²,

Sawyer³

et al. 2015

Macromolecules

250

185

View full text Add to dashboard Cite

show abstract

“…A characteristic feature that enhances PTFE's utility as a solid lubricant is the fact that it easily forms chemically stable transfer-films on a counter-surface, even at low pressures of only a few kPa ( Figure 3) [95]. Once the formation of the transfer-film on the counter-surface occurs, the frictional interface consists of PTFE-PTFE contacts, inducing low friction.…”

Section: Solid Lubrication With Ptfementioning

confidence: 99%

“…The ease with which PTFE can be transferred onto surfaces of materials, including metals and glass, provides a practical route for tribological properties to be modified. The molecularscale mechanisms involved in the formation of transfer films are still not completely understood, making them a subject of active computational [96] and experimental research [95,97,98]. Despite its attractive frictional properties, pure PTFE typically suffers from poor wear resistance, reflected by specific wear rates on the order of 10 -4 mm 3 /Nm [97,[99][100][101].…”

Section: Solid Lubrication With Ptfementioning

confidence: 99%

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Synergetic effects of surface texturing and solid lubricants to tailor friction and wear – A review

Rosenkranz

Costa

Baykara

et al. 2021

Tribology International

332

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Surface texturing and solid lubricants have demonstrated the ability to substantially reduce friction and wear under dry conditions. In recent decades, these two technologies have been combined to leverage the advantages of both for superior tribological performance. This review article first summarizes the state-of-the-art regarding surface texturing and solid lubricants, including soft metals, polytetrafluoroethylene, diamond-like carbon and 2D layered materials. Then, the synergy between surface textures and solid lubricants is discussed, with particular emphasis on the underlying mechanisms. Finally, gaps in the existing understanding of these synergies are identified and opportunities for future research are suggested.

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“…These mechanical properties have a direct impact on the friction behavior of PTFE. When sliding against highly polished surfaces of materials such as glass [35] and silicon oxide [58] at low sliding speeds (≤1 mm/s) and relatively high temperatures, a very thin film (10–40 nm) of PTFE is transferred to the countersurface, leading to an extremely low friction coefficient at room temperature (~0.04). These films are crystalline and highly ordered, even more than the bulk PTFE polymer, and form when PTFE strands consecutively attach to the substrate and are pulled off from the bulk material to yield an array of parallel fibers [59].…”

Section: Discussionmentioning

confidence: 99%

Influence of Femtosecond Laser Surface Nanotexturing on the Friction Behavior of Silicon Sliding Against PTFE

et al. 2019

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The aim of the present work was to investigate the influence of laser-induced periodic surface structures (LIPSS) produced by femtosecond laser on the friction behavior of silicon sliding on polytetrafluoroethylene (PTFE) in unlubricated conditions. Tribological tests were performed on polished and textured samples in air using a ball-on-flat nanotribometer, in order to evaluate the friction coefficient of polished and textured silicon samples, parallel and perpendicularly to the LIPSS orientation. In the polished specimens, the friction coefficient decreases with testing time at 5 mN, while it increases slightly at 25 mN. It also decreases with increasing applied load. For the textured specimens, the friction coefficient tends to decrease with testing time in both sliding directions studied. In the parallel sliding direction, the friction coefficient decreases with increasing load, attaining values similar to those measured for the polished specimen, while it is independent of the applied load in the perpendicular sliding direction, exhibiting values lower than in the two other cases. These results can be explained by variations in the main contributions to friction and in the wear mechanisms. The influence of the temperature increase at the interface and the consequent changes in the crystalline phases of PTFE are also considered.

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Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

Cited by 6 publications

References 32 publications

PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films

PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films

Synergetic effects of surface texturing and solid lubricants to tailor friction and wear – A review

Influence of Femtosecond Laser Surface Nanotexturing on the Friction Behavior of Silicon Sliding Against PTFE

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