Wear-Induced Microstructural and Chemical Changes in Poly[tetrafluoroethylene-<i>co</i>-(perfluoroalkyl vinyl ether)] (PFA)

Sidebottom, Mark A.; Junk, Christopher P.; Salerno, Holly L. S.; Burch, Heidi E.; Blackman, Gregory S.; Krick, Brandon A.

doi:10.1021/acs.macromol.8b01564

Cited by 10 publications

(5 citation statements)

References 32 publications

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“…28,29,36,39,40 It has been demonstrated that the tribochemical breaking of C−C bonds in the PTFE backbone occurs in non-ultralow wear PTFE systems, and even unfilled PTFE and perfluoroalkoxy polymer (a random copolymer of TFE and a few mol % of perfluoroalkyl vinyl ether). 61,62 It is hypothesized that tribochemically generated carboxyl/carboxylic acid end groups are not unique to ultralow wear PTFE; they are expected to form in higher wearing PTFE composites and unfilled PTFE but only accumulate measurably (via IR) in the tribofilms of the ultralow wear composites. This occurs because conditions for ultralow wear PTFE promoted extended shearing cycles on the same region of the polymer, which created progressively more carboxylic acid end groups that bond to nearby metallic surfaces to form protective films.…”

Section: Resultsmentioning

confidence: 99%

Ultralow Wear PTFE-Based Polymer Composites—The Role of Water and Tribochemistry

Campbell¹,

Sidebottom

Atkinson³

et al. 2019

Macromolecules

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The role of water in the tribochemical mechanisms of ultralow wear polytetrafluoroethylene (PTFE) composites was investigated by studying 10 and 20 wt % polyether ether ketone (PEEK)-filled and 5 wt % αAl2O3-filled PTFE composites. These composites were run against stainless-steel substrates in humidity, water, and dry nitrogen environments. The results showed that the wear behavior of both composites was significantly affected by the sliding environment. Both composites achieved remarkably low wear rates in humidity because of tribochemically generated carboxylate end groups that anchored the polymer transfer films to the steel substrate. In nitrogen, PTFE–PEEK outperformed PTFE−αAl2O3 because of polar carbonyl groups on PEEK, which increased the surface energy of PEEK, aiding it in adhering to the substrate and resulting in a transfer film. Both composites in water exhibited high wear. The water oversaturated the functional groups at the end of the polymer chains and prevented the formation of a transfer film.

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Section: Resultsmentioning

confidence: 99%

Ultralow Wear PTFE-Based Polymer Composites—The Role of Water and Tribochemistry

Campbell¹,

Sidebottom

Atkinson³

et al. 2019

Macromolecules

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“…The second heating cycle (Figure 3) shows an endotherm peak, in the range of −10–10 °C, which corresponds to the solid−solid transition of PFA crystallites from the triclinic to hexagonal crystalline structure. [ 12 ] This transition can be attributed to greater molecular mobility of the PFA side chain, due to the oxygen present in the structure, which allows a rearrangement in the crystal in the transition region between the crystal and amorphous phase during heating or cooling.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, research efforts were trying to modify PTFE in different ways to overcome these shortcomings, because modified PTFE significantly reduced melt viscosity by lowering the crystallinity through the incorporation of bulky comonomers [11] into the polymer main chain. [6] In this way, copolymerizing perfluoroalkyl vinyl ether with PTFE led to tetrafluoroethylene-perfluoroalkyl vinylether copolymer (PFA) (Figure 1b), which exhibit reduced crystallinity, [12] lower melting points and making the polymer easier to process. [13] The consumption of fluoropolymers has increased over the last decade, as technological advancement has required their unique properties in several applications, ranging from the biomedical and aerospace industry to everyday household appliances.…”

Section: Introductionmentioning

confidence: 99%

Recycling Tetrafluoroethylene–Perfluoroalkyl Vinylether Copolymer (PFA) Using Extrusion Process

Romoaldo

Francisquetti

Simon

et al. 2022

Macro Materials & Eng

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Tetrafluoroethylene–perfluoroalkyl vinylether copolymer (PFA) has a broad application ranging from biomedical and aerospace to corroding environments in the chemical industry. Despite a low share in end‐of‐life products, PFA processing can produce up to 30% of waste. Thus, understanding how recycled fluorinated polymers affect product performance is crucial to ensure primary recycling, besides economic and environmental reasons. In this paper, the utilization feasibility of PFA waste materials is investigated, i.e., recycled PFA (PFAr) in closed‐loop recycling. The effect of PFAr loading (5–100 wt.%) on the thermal, mechanical, rheological, and color properties and chemical resistance are studied. Thermal properties and chemical resistance showed no significant changes in all ranges of PFAr content tested. The addition of higher loads of PFAr (≥50 wt.%) leads to a reduction in mechanical properties, particularly stress‐strength analysis and elongation at break. However, elastic modulus and hardness have improved concurrently with an increase in the degree of crystallinity. The decrease in complex viscosity and yellowing of the samples occurred probably induced by a polymer chain degradation. Despite that, the addition of up to 10 wt.% of PFAr proved to be an effective alternative to reusing PFA residues based on mechanical recycling.

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“…However, the effect of low temperature on transfer film formation is controversial, as shown in figure 5(b). The formation of a transfer film is strongly related to tribochemical reactions such as chain section, chelating reaction between carboxylic group and metal substrate, as well as structure orientation, among others [112,113,[122][123][124][125][126]. Transfer films strongly adhere to the counterface and have low shearing force.…”

Section: Transfer Film and Tribochemistrymentioning

confidence: 99%

Progresses on cryo-tribology: lubrication mechanisms, detection methods and applications

Cui

Hongzhan

Zhao

et al. 2023

Int. J. Extrem. Manuf.

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Tribology at cryogenic temperatures has attracted people’s attention since the 1950s with the acceleration of its applications on hi-tech equipment such as the cryogenic wind tunnel, liquid fuel rocket, space infrared telescope, superconducting device, planetary exploration, which requires solid lubrication for moving parts at low temperature down to 4 K in cryogenic liquid, gaseous or vacuum environments. Here the research progresses on cryo-tribology are reviewed. Tribological properties and mechanisms of solid lubricants listed as carbon material, molybdenum disulfide (MoS2), polymer and polymer-based composite, etc. with decreasing temperature are summarized. The friction coefficient was found to increase with decreasing temperature induced by thermally activated processes. The mechanism of transfer film formation should be noticed as a significant way to promote the tribological properties of the solid lubricant. On the other hand, applications of solid lubrication on moving parts under cryogenic conditions such as the spherical plain bearing, roller bearing are introduced. Tribological test technology of materials and bearings at cryogenic temperatures is summarized where the environmental control, motion and loading realization, as well as friction and wear measurement together at low-temperature environment result in the difficulties and challenges of the low-temperature tribotester. It is worth mentioning that novel technologies and tribotesters were developed for tribo-tests and tribological studies of solid lubricant, spherical plain bearing and roller bearing respectively by overcoming the limitation on cooling in vacuum, resolution of friction measurement, etc., and concentrating on in-situ observation of friction interface aiming to not only promote a deep understanding of friction and wear mechanism at low temperatures, but also give insights into performance of moving parts or components in cryogenic applications.

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Wear-Induced Microstructural and Chemical Changes in Poly[tetrafluoroethylene-co-(perfluoroalkyl vinyl ether)] (PFA)

Cited by 10 publications

References 32 publications

Ultralow Wear PTFE-Based Polymer Composites—The Role of Water and Tribochemistry

Ultralow Wear PTFE-Based Polymer Composites—The Role of Water and Tribochemistry

Recycling Tetrafluoroethylene–Perfluoroalkyl Vinylether Copolymer (PFA) Using Extrusion Process

Progresses on cryo-tribology: lubrication mechanisms, detection methods and applications

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