Tribological Properties Of Polytetrafluoroethylene Research Articles

Influence of different types of counterbodies on tribotechnical properties of polytetrafluoroethylene

This paper presents the results of a study of different types of counterbodies on the tribological properties of polytetrafluoroethylene (PTFE). The characteristics of the polymer, the roughness and hardness of counterbodies made of the following materials are given: copper, aluminum, brass and steel grade 45. It is shown that the best wear resistance is obtained for a friction pair – polytetrafluoroethylene with steel grade 45 and brass. The friction surfaces of the counterbodies and the polymer were studied by optical, electron microscopy, and IR spectroscopy.

Effect of thermal oxidative ageing on the molecular structure and tribological properties of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE), which has an extremely low coefficient of friction and good thermal and chemical stability, is widely used as a self-lubricating material. In this study, the thermal oxidative-ageing mechanisms of PTFE were studied using infrared spectroscopy and molecular dynamics simulations, and the influence of the thermal oxidative-ageing time on its tribological properties was investigated under a high load (20 MPa). Results indicated that thermal oxidative-ageing resulted in oxidation fracture, generating CF2O products, followed by further oxidation to CFO2 as ageing time increased. The dynamic friction coefficient of PTFE fluctuated significantly under heavy load, and its wear rate fluctuated over a small range but showed a decreasing trend with increased ageing.

Quantitative Measurement of Morphological Characteristics of PTFE Composite Transfer Films Based on Computer Graphics

In this paper, the tribological properties of polytetrafluoroethylene (PTFE) composites filled with Nano-ZrO2 and polyetheretherketone (PEEK) particles were tested for sliding friction against a counterpart metal (ASTM 1045 steel) using a linear reciprocating friction and wear experimental machine. Data on tribological performance and optical images of the transfer film were obtained at various friction stages for the material. MATLAB software was employed to develop quantitative analysis procedures for the morphological characteristics of the transfer film. The program enables image enhancement and morphological processing of transfer film images, then identifies, extracts, and quantifies the geometric and textural properties of the transfer film as a foundation for analyzing the variation of the characteristics and their relationship to the tribological properties of the material. The results demonstrated that the geometric, morphological, and textural characteristics of the transfer film were dynamically developing during the friction process, with noticeable differences between various friction stages and a significant impact on the tribological properties of the material. Quantitative analysis revealed a good correlation between the trends of some morphological and textural characteristics (the coverage, area, diameter, roundness, consistency, and texture entropy) of the transfer film and the wear resistance of the PTFE composite. Therefore, these morphological and textural characteristics can thus be used to quantify the transfer film quality and utilized as an indirect indicator of the tribological properties of the material.

Tribological properties of PTFE/Kevlar fabric composites at different twill orientations

In this study, tribological properties of Polytetrafluoroethylene (PTFE)/Kevlar fabric composites at different orientations under different contact pressures (p) and sliding velocities (v) were investigated. The friction surface, debris and transfer film were analyzed to reveal the tribological behavior of the fabric composite. Results indicated that different wear mechanisms at different twill orientations lead to changes in tribological properties. The fabric composite with right twill (RT) has better tribological properties under high pv values and is sensitive to the change of load. The left twill (LT) shows better properties under low pv values and is sensitive to the change of velocity. The comparison of different twill orientations has implications for the structural design of fabric composites under different application conditions.

Effect of SiO2 on the tribological properties of PTFE sliding against Cu: a molecular dynamics simulation

PurposeThe purpose of this paper is to investigate the effect of SiO2 on the tribological properties of polytetrafluoroethylene (PTFE) composites from an atomic level.Design/methodology/approachEffect of SiO2 on the tribological properties of PTFE sliding against Cu was studied by molecular dynamics (MD) simulations to explore the inherent mechanisms from an atomic level.FindingsSiO2 had a higher interaction energy with PTFE than copper, which contributed to an increase of interfacial temperature and velocity with severe adhesive wear on the PTFE molecules.Originality/valueThis study reveals the mechanism of SiO2 on the friction and wear behavior of PTFE by MD simulation.

Experimental and Analytical Investigations on Tribological Properties of PTFE/AP Composites

The tribological properties of polytetrafluoroethylene (PTFE)/AP (poly(para-phenyleneterephthalamide) (PPTA) pulp) composites under different test conditions (load: 2N, 10N; frequency: 1 Hz, 4 Hz; amplitude: 2 mm, 8 mm) were holistically evaluated. PTFE/AP composites with different AP mass ratios of 3%, 6%, and 12% as a skeleton support material were prepared. The coefficient of friction (COF) and wear rate were determined on a ball-on-disk tribometer. Furthermore, the morphology, element composition, and chemical structure of the transfer membrane were analyzed accordingly. The relationships between load, frequency, amplitude, and tribological properties were further investigated. According to the wear mechanism, AP enables effective improvement in the stiffness and wear resistance, which is also conducive to the formation of transfer films.

Tribological properties of PAO40@SiO2/PTFE/aramid fabric composites subjected to heavy-loading conditions

PAO40@SiO2 microcapsules (PSMS) were prepared by adsorbing Poly α-olefin lubricating oil 40# (PAO40) with hollowed SiO2 particles. The tribological properties of polytetrafluoroethylene (PTFE)/aramid fabric composites at different microcapsules contents were evaluated by the ring-block tests. The friction coefficient and wear rate of PTFE/aramid fabric composites containing 6 wt% PSMS (Fabric-6% PSMS) were reduced by 42.9% and 31.5% respectively, as opposed to those of neat PTFE/aramid fabric composites (Fabric-0%). The service life of Fabric-6% PSMS under radial pressure of 240 MPa was increased by 5.3 times as compared with that of Fabric-0%. The wear mechanisms of Fabric-6% PSMS revealed that SiO2 particles promoted the formation of metal-F bonds on the shaft surfaces and further improved the abrasive resistance of transfer films.

Effect of Recovered Silicon Filler Inclusion on Mechanical and Tribological Properties of Polytetrafluoroethylene (PTFE) Composite

Effect of Recovered Silicon Filler Inclusion on Mechanical and Tribological Properties of Polytetrafluoroethylene (PTFE) Composite

Synergistic modification of the tribological properties of polytetrafluoroethylene with polyimide and boron nitride

Polytetrafluoroethylene (PTFE) blended with polyimide (PI) and filled with boron nitride (BN) is prepared through cold pressing and sintering for composites with remarkable wear resistance and reduced coefficient of friction (COF). The characterizations show that BN and PI at different levels, improve the hardness, dynamic thermo-mechanical modulus, thermal conductivity, and tribological properties of PTFE. PI boosts the dispersion and bonding of BN in PTFE. In dry sliding friction of a block-on-ring tribometer, the wear rate and COF of 10:10:80 BN/PI/PTFE reduce to almost 1/300 and 80% of those of pure PTFE, respectively, as the wear mechanism transition from being adhesive to partially abrasive. This occurs only when the additives BN and PI induce a synergistic effect, that is, at concentrations that are not higher than ca. 10 wt% and 15 wt%, respectively. The obvious agglomeration at high percentages of added PI and severe conditions (400 N and 400 rpm) induce strong adhesive failure. The variations in the tensile properties, hardness, crystallization, and microstructure of the composites correspond to different effects. The multiple parameters of the plots of wear and friction are transformed into their contour curves. The mechanism transition maps aid in understanding the influence of various test conditions and composite compositions on the contact surfaces in the space-time framework of wear.

Tribological Behavior of PTFE Composites Filled with PEEK and Nano-ZrO2

In order to study the tribological properties of PTFE modified by hard nanoparticles and soft polymer under dry friction conditions, the tribological properties of polytetrafluoroethylene (PTFE) filled with different volume contents of polyether ether ketone (PEEK) and nano-ZrO2 were investigated at a linear speed of 2 m/s, normal load of 200 N, and ambient temperature conditions for 60 min using a block-on-ring wear tester. A multiple-layer feedforward artificial neutral network (ANN) was used to simulate and analyze the friction coefficient and volume wear rate. The results showed that the friction coefficient and volume wear rate of PTFE composites were effectively reduced when nano-ZrO2 and PEEK were filled separately or simultaneously. The best tribological properties were obtained when the composites were filled with 5–8 vol% nano-ZrO2 and 20 vol% PEEK simultaneously; the volume wear rate was only 1.29 × 10−6 mm3/Nm and the friction coefficient was only 0.15. An ANN can accurately simulate and predict the friction coefficient and volume wear rate of composites, and the predicted results were consistent with the experimental results. A groove appeared in the volume wear rate simulation diagram when the volume content of nano-ZrO2 was about 7% with or without PEEK. This phenomenon indicates that the composites in this region had a lower volume wear rate. Therefore, the addition of nano-ZrO2 and PEEK can effectively improve the tribological properties of PTFE. As a simulation analysis method, an ANN can accurately analyze and predict the tribological properties of composites.

Influence of the gamma irradiation dose on tribological property of polytetrafluoroethylene

Abstract In this study, the evolution of structure, nanomechanical and tribological properties of polytetrafluoroethylene (PTFE) induced by gamma-ray irradiation with dose up to 20 MGy were investigated, and the frictional failure mechanism after irradiation was also discussed. The structural analyses reveal that the crystallinity degree of PTFE increases significantly with the increase of irradiation dose. The functional groups of COOH, C C and -(CH2)n-are produced due to surface chemical reaction induced by irradiation above 5 MGy dose. High density cracks appear on the surface and both the length and width of the crack propagate with the increase of irradiation dose. Both the nanohardness and Young's Modulus of the irradiated PTFE increase significantly when the irradiation dose is lower than 5 MGy. Further exposure leads to the decrease of nanohardness. The mean friction coefficient increases from 0.035 to 0.12 after 0.3 MGy irradiation and turn to saturation with further increasing irradiation dose. However, after 5 MGy gamma-ray irradiation, the wear rate of PTFE increases significantly, the present of crack on the surface and subsurface accelerates the peeling of the bulk material during the sliding process and results in the wear deterioration.

SCLEROMETRIC AND TRIBOLOGICAL PROPERTIES OF POLYTETRAFLUOROETHYLENE WITH 40% BRONZE CONTENT FORMED BY ELECTRON BEAM IRRADIATION

The paper focuses on the improvement of sclerometric and tribological properties of polytetrafluoroethylene (PTFE) with 40% bronze content implied by irradiation with an electron beam of 10 MeV and a power of 10 kW, in a dose of 26–156 kGy. The results of the study confirm that radiation modification of the PTFE-bronze composite causes structural changes induced by breaking of bonds in long PTFE chains and the branching of the polymer structure. As a result, an increase in such properties as the wear resistance ratio, Wβ, is observed. In addition, sclerometric tests have shown that, with an increase of the absorbed radiation dose, the grooveto- elevation area ratio changes during scratching, which indicates a change in the micromechanism of wear, i.e. the material undergoes ploughing. From the operating point of view, the most important were tribological tests, which were carried out on a pin-on-disc test stand (T-01). The tests showed a nearly fourfold reduction in wear at a load of 20 N and more than a threefold reduction at 40 N. Controlled radiation modification leads to improved properties of the PTFE-bronze composite, which may result in a wider range of its applications.

Improved mechanical and tribological properties of polytetrafluoroethylene reinforced by carbon nanotubes: A molecular dynamics study

Mechanical and tribological properties of polytetrafluoroethylene (PTFE) reinforced with carbon nanotubes (CNTs) are studied by a molecular dynamics (MD) simulation to explore inherent interactions and wear mechanisms of polymer nanocomposites from an atomic scale. The friction models of polymer sliding against metal are developed to examine the friction coefficient and wear rate. The mechanical properties of pure PTFE are also analyzed to explain the inherent mechanisms of friction reduction and wear resistance improvement. The MD simulated results show that the Young’s modulus and shear stress of PTFE increase by 136.58% and 236.3% after carbon nanotubes reinforcement, respectively. The average friction coefficient of PTFE in the steady stage sliding against Cu layer under normal conditions decreases from 0.169 to 0.127 after CNTs reinforcement. The interaction potential energy between CNT and PTFE was calculated to interpret the improvement effect of CNT. The inherent mechanisms of the enhanced mechanical and tribological properties of PTFE are emphatically discussed and interpreted from an atomic view by analyzing the variations of the radius distribution function, relative concentrations and temperature in the thickness direction.

Tribological Behavior of PTFE Composites Filled with PEEK and Nano-Al2O3

ABSTRACT In this study, the tribological properties of polytetrafluoroethylene (PTFE) composites filled with polyetheretherketone (PEEK) and nano-Al2O3 particles were studied using a block-on-ring wear tester. The tribological performance of the composites was affected by the experimental parameters (sliding speed, normal load, and environmental temperature) and the composites achieved a high-speed sliding friction state. The results showed that the PEEK and nano-Al2O3 particles significantly improved the wear resistance of the PTFE composites. In addition, the nano-Al2O3 particles increased the hardness of the composites and enhanced the mechanical properties to enable applications in a wider range of industrial fields. The effects of the sliding speed and normal load on the tribological properties were more significant than that of the environmental temperature. In addition, the entire wear process was divided into three stages (the initial wear stage, severe wear transition stage, and ultralow stable wear stage), according to the evolution of the tribological characteristics (wear rate, morphology of the worn surface and transfer film, and wear debris morphology).

Tribological properties of polytetrafluoroethylene at cryogenic temperatures

Tribological properties of polytetrafluoroethylene at cryogenic temperatures

Proton irradiation effects on the structural and tribological properties of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was irradiated with protons in a ground-based simulation facility to study the effects of proton irradiation on the structural and tribological properties of PTFE. The structural changes were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total-reflection FTIR (ATR-FTIR), while the tribological properties were evaluated by friction and wear tests. It was found that proton irradiation induced the degradation of PTFE molecular chains, resulting in the increase of C concentration and the decrease in F concentration on the sample surfaces, and the surface chemical structure and morphology of the samples changed, which affected the friction coefficient and decreased the wear rate of the specimens as the friction and wear tests revealed.

Tribological Properties of PTFE and PTFE Composites at Different Temperatures

The friction and wear properties of polytetrafluoroethylene (PTFE) and its composites with fillers such as bronze, glass fiber, carbon fiber, carbon, graphite, and polymer were studied at ambient temperature and high temperature. The wear resistance and hardness were enhanced by the fillers. Results showed that the wear resistance of all composites was much higher than that of pure PTFE. Pure PTFE has the lowest friction coefficient at ambient temperature (temperature: 23 ± 2°C, humidity: 50 ± 10%) but highest friction coefficient at high temperature (above 100°C). The PTFE composite filled with bronze showed the best wear resistance at ambient temperature but the poorest wear resistance at high temperature. The carbon-graphite- or polymer-filled PTFE composite showed a lower friction coefficient and moderate wear resistance at both ambient and high temperature.

The Wear and Friction Behavior of Novel Polytetrafluoroethylene/Expanded Graphite Nanocomposites for Tribology Application

The tribological properties of polytetrafluoroethylene (PTFE)/expanded graphite (EG) nanocomposites were evaluated on a pin-on-disk wear tester under dry conditions for the first time. Scanning electron microscopy (SEM) was used to examine worn surfaces and debris of the worn samples. The wear rate and coefficient of friction of 2 wt. % EG filled nanocomposite were reduced approximately 162 times and 38%, respectively. The significant decrease in wear rate was attributed to a thin and tenacious transfer film on the counter-surface. However, when 5 wt. % EG was filled into the PTFE/EG nanocomposite, the wear rate did not decrease further.

Mechanical and tribological behavior of polytetrafluoroethylene composites reinforced by carbon nanotubes and poly-p-oxybenzoate

Effects of microscale poly- p-oxybenzoate (trade name Ekonol), nanoscale carbon nanotubes (CNTs) and multiscale fillers on the mechanical, creep and tribological properties of polytetrafluoroethylene (PTFE) are studied. Results reveal that the multiscale PTFE composite with 20 wt% Ekonol and 1 wt% CNTs has the highest tensile strength and modulus as well as relatively modest elongation at break compared to pure PTFE, micro and nanoscale PTFE composites. In addition, the combination of Ekonol and CNT fillers leads to a significant improvement in creep resistance of PTFE composites. Scanning electron microscopic observation of tensile fracture surfaces indicates that for multiscale composite, the surfaces of Ekonol particles are wrapped by individual CNTs and the bridge of CNTs between Ekonol particles is formed. Also, the combination of Ekonol and CNT fillers slightly increases the friction coefficient of multiscale composite but greatly decreases the wear rate by approximately four orders of magnitude compared with pure PTFE. Scanning electron microscopic observation of the worn surfaces shows that the wear surface of the multiscale composite is very smooth. Therefore, the wear resistance significantly improved. The synergetic role of multiscale fillers is expected to open up new opportunities to formulate high-performance PTFE composites.

Tribological properties of polytetrafluoroethylene as additive in titanium complex grease

PurposeThe purpose of this paper is to study, analyze and present the lubricating mechanism and tribological properties of two types of oil‐based titanium complex grease containing Polytetrafluoroethylene (PTFE).Design/methodology/approachTwo types of oil‐based sebacic acid/stearic acid titanium complex greases containing PTFE additive were synthesized using 3 L reaction vessel, and the base oils including neopentyl polyol ester and mixed oil of 650SN and neopentyl polyol (1:1.8). Friction‐reduction, antiwear, and load‐carrying properties of greases were evaluated using a four‐ball tester, and their dropping point and penetration were characterized using relevant ASTM standards. Morphologies of wear scar and chemical states of typical elements on worn surfaces were characterized by means of scanning electron microscope and X‐ray photoelectron spectroscopy, respectively.FindingsTribological results show that titanium complex grease containing PTFE had better friction‐reduction and antiwear properties than base grease. However, PTFE could not improve the load‐carrying capacity of base grease. Moreover, a synergistic effect between deposited film and adsorptive film contributes to good tribological properties of titanium complex grease.Practical implicationsSuch a very useful lubricating material could be used in industrial applications including steel plants, power plants, packaging, and fertilizer industries.Originality/valueThe lubricating mechanism of titanium complex grease containing PTFE was proposed by tribochemical analysis of worn surfaces. The mechanism should become the direction of the theoretical and applied research of grease in the future.