Papers by Keyword: PTFE

Abstract: In this paper, the thermal failure (seizure or melting) of hybrid radial bearing (PEEK ring-PTFE composite retainer and alumina ball) under rolling contact fatigue test was investigated. For effective operation of equipment in various environments such as dirty, harmful or corrosion situations, the radial PEEK-PTFE hybrid bearings were produced by machining. The PEEK accumulation layer containing carbon graphite was formed on the raceway of bearing's inner ring at 1200-1500 rpm rotation speed. Due to the self-lubrication of the PEEK composite accumulation layer as solid lubricant, the operation temperature in the hybrid bearing was lower than that of all PEEK radial bearing, and the load capacity of the PEEK bearings could be improved. Moreover, it was found that the PEEK composite film which is formed from the PEEK composite layer protected the raceway from the friction heat.

Abstract: Polymer bearings are attracting more and more attention due to the advantages on light weight, chemical and corrosion resistant, etc. PTFE owns the third-lowest friction coefficient within any known solid material, which makes it a considerable polymer material for bearing producing. In the present study, RCF tests under dry condition were carried out, and the relationship between failure and temperature of PTFE thrust bearings was investigated.

Abstract: During the irradiation of high molecular weight poly (tetrafluoroethylene) (PTFE) in presence of oxygen perfluoroalkyl (peroxy) radicals and functional groups are formed which allow chemical coupling reactions (cc = chemical compatibilized) with oils and plastics. The micropowder resulting from the irradiation of PTFE are used in base oils to improve the tribological properties significantly if oil molecules are covalently linked to primary PTFE particles in the oil dispersion. These oil-PTFE-cc-dispersions show primarily anti-wear (AW) properties. The use of additional reactive groups (e.g. phosphite groups) in the oil gives the dispersions extreme pressure (EP) properties additionally. This article demonstrates the usefulness of the oil-PTFE-cc-dispersions in rolling bearings and in ropes using phosphite-modified PTFE products as additive in lubricants. The investigations are completed by wear tests with different contact geometries. A model is shown to explain the effect of phosphite groups on 100Cr6 metallic surfaces.Keyword s: PTFE, high performance lubricant, oil-PTFE-cc dispersion

Abstract: This study investigates the application of PTFE wicks to flat-plate loop heat pipes (FLHPs). PTFE’s low heat transfer coefficient effectively prevents heat-leakage, which is a problem with using metal wicks, lowering the operating temperature and pressure. This paper uses PTFE particles to form wicks, and the effect of PTFE on flat-plate LHP performance is investigated. Experimental results shows that the highest heat load reached was 100W, with lowest thermal resistance of 0.61°C/W, and heat flux of about 10W/cm², For the wick properties, the wick had an effective pore radius of the wick was around 9.2μm, porosity of 47%, and permeability of 1.0 x 10^-12m². Compared to the highest heat flux reported in literature thus far for PTFE flat-plate LHPs, the heat flux in this study was enhanced by around 50%.

Abstract: Due to the advantage on low coefficient and self-lubricant, PPS races-PTFE retainer hybrid polymer bearings can offer better service performance under certain condition. In our previous study, the relationship between friction coefficient and rotation speed was investigated, and formation of black layer was found. In the present study, EPMA was introduced to investigate the component and thickness of the black layers. Based on the observations, the relationship between friction coefficient, solid lubricant layer and thrust load was also discussed.

Abstract: Surface modification of polytetrafluoroethylene (PTFE) fiber by plasma grafting polymerization with acrylamide (AAm) was studied to improve the compatibility between polyacetal (POM) and PTFE. The best modified PTFE manufactured by self-designed plasma polymerization was investigated and denoted as AAm (20wt%)-g (plasma 30min)-PTFE. The grafting polymerization is successful and shown by ESCA spectra of modified PTFE fibers. It is also proved by SEM photographs and the improvement of properties of the POM/PTFE composites. As a result, the friction coefficients, Taber wear factors, and impact strengths of composites with 85wt% of POM and 15wt% of a variety of PTFEs were investigated. The frictional coefficient of POM/ AAm (20wt%)-g (plasma 30min)-PTFE deceased to 0.162; while that of POM/PTFE was 0.174. Taber wear factor of the composite significantly decreased from 5.2 to 1.5 when the PTFE was replaced by AAm-g (plasma)-PTFE. Meanwhile, the impact strength increased from 6.1 kg-cm/cm (POM/PTFE) to 9.3kg-cm/cm (POM/ AAm-g (plasma)-PTFE). Besides, the multi-yield behaviors were found in the Stress-Strain curves of composites with modified PTFE fibers.

Abstract: With the rapid development of advanced science and technology, the performance requirements of the PTFE fabric composite is rapidly increase. In this work, the dry friction tests of PTFE braided composites were carried out on high-speed Tribo-tester analysing the influence of different working conditions to the friction temperature and humidity in the measurement of friction characteristics experiments. Scanning electron microscopy (SEM) was utilized to examine composite microstructures and study modes of failure. Energy spectrometer analysis was also performed to study the wear surface and the ingredient of the debris in an effort to get the mechanism of the composites damage.

Abstract: Co-deposition process of amorphous nickel and PTFE particles in the presence of Ni (OH)₂ carrier suspended in the bath by magnetic stirring, was investigated. Composite Ni-P+Ni (OH)₂+PTFE coatings and comparative Ni-P deposits, were electrodeposited on low carbon steel substrate under galvanostatic conditions at room temperature. The physical and chemical characterization of the coatings was carried out using X-Ray diffraction analysis and microanalysis, stereometric quantitative microscopy and atomic absorption spectroscopy. The optimum production conditions of the composite coatings based on the Ni-P matrix into which PTFE and Ni (OH)₂ components can be embedded uniformly, were found.

Abstract: In this work an attempt of production of the composite coatings based on the amorphous nickel matrix with embedded different carrier (TiO₂, Ni (OH)₂) and PTFE particles as the composite component, was undertaken. The relaxation characteristics of the electrodeposition process of the composite Ni-P+TiO₂+PTFE and Ni-P+Ni (OH)₂+PTFE coatings was carried out. It was found that the obtained J = f (t) relaxation curves correlate with electrodeposition conditions of the coatings determined on the basis of the E = f (J) polarization curves. Usability of the relaxation methods for determination of the electrodeposition parameters of the composite coatings was also discussed.

Abstract: We investigate the effects of polytetrafluoroethylene (PTFE) on organic photovoltaic (OPV) devices with structure of ITO/PTFE/PEDOT:PSS/P3HT:PCBM/PTFE/Al by inserting thermally evaporated PTFE films between indium-tin-oxide (ITO) and PEDOT:PSS layers, and also between P3HT:PCBM and Al, respectively. Significant improvement in terms of open-circuit voltage, Fill factor (FF), and thereby in its commensurate power conversion efficiency is achieved compared to devices with PEDOT:PSS and LiF buffer layers. The OPVs performance enhancement is attributed to the formation of an artificial dipole layer resulting from the rich, negatively charged fluorine that facilitates the charge extraction process.