Effect of simulation conditions on friction in polytetrafluoroethylene (PTFE)

Barry, Peter R.; Jang, Inkook; Perry, Scott S.; Sawyer, W. Gregory; Sinnott, Susan B.; Phillpot, Simon R.

doi:10.1007/s10820-007-9087-4

Cited by 14 publications

(10 citation statements)

References 9 publications

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“…The sliding was given parallel to PTFE chains because this direction would be energetically stable in sliding process. 13 Also, the velocity was set as 100 m/s to observe the sliding effects with reasonable computation time. The bottom layer of the carbon backbone in PTFE was completely fixed during the QCMD simulation.…”

Section: Resultsmentioning

confidence: 99%

“…In the field of nanotribology, a computational chemistry method is a powerful tool for analyzing the mechanism of friction at the atomistic scale, and they have been extensively applied so far. − The PTFE sliding system has also been investigated by this method. , Recently, the initial stage of the transfer film formation onto metallic surface, which was supported by interfacial chemical bonds, was successfully simulated by our original quantum chemical molecular dynamics (QCMD) method . Accordingly, in this study, the tribochemical reaction between PTFE and metallic surface after forming transfer film was focused on since the change in the chemically stable polymer structure is probably caused by interaction with environmental molecules, viz.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Reaction Mechanism of Polytetrafluoroethylene on Aluminum Surface under Friction Condition

et al. 2014

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To develop a novel shearing resin material, it is necessary to understand the mechanism of friction-induced chemistry during the friction process. For this purpose, the chemical reaction of the polytetrafluoroethylene (PTFE) resin on an aluminum surface during friction was first focused on and investigated by a quantum chemical molecular dynamics method. From our simulation, an aluminum atom on a native oxide of aluminum surface led to a tribochemical reaction, which included defluorination of PTFE and aluminum fluoride formation. It was inferred that the aluminum surface acted as a catalytic Lewis acid in which the fluorine atom was removed from the PTFE polymer chain. The tribological performance of the investigated system was reduced by the forming of aluminum fluoride since a self-lubrication by PTFE was inhibited by an interfacial electrostatic repulsion. On the basis of our study, it was suggested that the key to increase tribological performance was a chemical reaction between reactive defluorinated PTFE and environmental water vapor to form a novel functional group on the PTFE chain.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical Reaction Mechanism of Polytetrafluoroethylene on Aluminum Surface under Friction Condition

et al. 2014

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“…For solving the above-described problem concerning the “nanotribology” of PTFE, it has been recognized that a computational chemistry method, such as molecular dynamics (MD), is a powerful tool for revealing the mechanism of friction on the atomistic scale. Such methods have thus been extensively applied, − and the PTFE system focused on in this study has been no exception. − Recently, the tribochemical reaction dynamics between PTFE and an aluminum oxide surface was investigated by an original quantum chemical MD (QCMD) method developed by the authors . This method was used to clarify the tribochemical reaction including the fluorination of the aluminum oxide surface and depolymerization by forming a carbon double bond in the PTFE molecule.…”

Section: Introductionmentioning

confidence: 99%

Effect of Tribochemical Reaction on Transfer-Film Formation by Poly(tetrafluoroethylene)

et al. 2014

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Understanding tribochemical reaction mechanisms is necessary to develop a novel resin material that can easily slide on metallic parts. For this purpose, the chemical reaction dynamics between poly(tetrafluoroethylene) (PTFE) resin and an aluminum surface were studied by using a quantum chemical molecular dynamics simulation [Onodera, T., et al. J. Phys. Chem. C 2014, 118, 5390−5396]. The study showed that the PTFE tribochemically reacted with the oxidized surface of aluminum, forming two chemical products, namely, aluminum fluoride and depolymerized PTFE with a carbon double bond at the terminus of the PTFE polymer chain. The carbon backbone was exposed by changing to a double bond configuration, although that in genuine PTFE is fully covered by fluorine atoms. The subsequent chemical reaction of the polymer that reacts with gaseous molecules in the atmosphere (i.e., nitrogen, oxygen, and water vapor) was first studied by density functional theory (DFT). The DFT calculation results show that the chemical reaction of PTFE with water vapor was the most likely to occur and that a carboxyl group was finally formed on the terminus of the PTFE chain. The effect of the chemical reaction with water vapor on formation of a PTFE transfer film on an aluminum surface, which directly affects tribological performance of the focusing system, was then investigated by a classical molecular dynamics method. By forming a carboxyl group as a reaction product with water vapor, the amount of PTFE transfer film on an aluminum fluoride surface (one of the tribochemical reaction products) was increased. On the other hand, less genuine PTFE (without a carboxyl group) was transferred to the aluminum fluoride. This study clarified that the transfer film is formed easily by the reaction of PTFE with atmospheric water vapor, which thereby improves the tribological performance of the PTFE/aluminum lubrication system.

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“…14−21 In fact, they have been used to study the friction of PTFE. 15,16 Using a moleculardynamics (MD) method, Jang et al analyzed the friction between a PTFE polymer chain and itself, and they found that the structural orientation of PTFE contributes to its tribological properties. 15 However, to the authors' knowledge, there has been no theoretical study that focuses on the behavior and formation of a PTFE transfer film on a metallic surface.…”

Section: Introductionmentioning

confidence: 99%

“…In the field of nanotribology, methods applying computational chemistry have emerged as a powerful tool for analyzing the mechanism of friction on the atomistic scale, and they have been extensively applied so far. − In fact, they have been used to study the friction of PTFE. , Using a molecular-dynamics (MD) method, Jang et al analyzed the friction between a PTFE polymer chain and itself, and they found that the structural orientation of PTFE contributes to its tribological properties . However, to the authors’ knowledge, there has been no theoretical study that focuses on the behavior and formation of a PTFE transfer film on a metallic surface.…”

Section: Introductionmentioning

confidence: 99%

Transfer-Film Formation Mechanism of Polytetrafluoroethylene: A Computational Chemistry Approach

et al. 2013

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A method based on computational chemistry is used to theoretically investigate the mechanism by which a transfer film, which strongly contributes to reducing friction and wear of a resin material, of polytetrafluoroethylene (PTFE) forms. The formation mechanism of a PTFE transfer film on an aluminum surface was investigated by a quantum chemistry simulation that showed that interfacial ionic interaction plays an important role in forming the transfer film on the counter aluminum surface. A tribochemical reaction, namely, the PTFE reacts with the aluminum surface as a Lewis acid to form a carbon radical, was found. It is inferred that this reaction is one of the key processes that produces the good tribological performance of PTFE. The influence of ambient water and nitrogen molecules on the transfer film formation was then studied by using a molecular dynamics method. The degree of PTFE transfer to a metallic surface in nitrogen gas was less than that in water vapor because the nitrogen molecules shielded the interfacial ionic interaction, which is a key factor in forming the transfer film. It is concluded that to form the transfer film a polar gas molecule or several polar groups in PTFE polymer chain is necessary.

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Effect of simulation conditions on friction in polytetrafluoroethylene (PTFE)

Abstract: We report the results of molecular-dynamics simulations of friction at polytetrafluoroethylene (PTFE) interfaces and show that the calculated tribological properties are robust against significant changes in the sliding speed and the morphology of the polymer.

Cited by 14 publications

References 9 publications

Chemical Reaction Mechanism of Polytetrafluoroethylene on Aluminum Surface under Friction Condition

Chemical Reaction Mechanism of Polytetrafluoroethylene on Aluminum Surface under Friction Condition

Effect of Tribochemical Reaction on Transfer-Film Formation by Poly(tetrafluoroethylene)

Transfer-Film Formation Mechanism of Polytetrafluoroethylene: A Computational Chemistry Approach

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