Polytetrafluoroethylene (PTFE) is an attractive membrane material due to its superior chemical resistance, thermal stability and strong hydrophobicity. However, PTFE hollow fiber membranes are ...challenging to produce by conventional technique due to the high solvent resistance and high melt viscosity of PTFE. In this study, novel PTFE hollow fiber membranes composed of pure PTFE nanofibers were firstly fabricated via a scalable and environment-friendly method based on emulsion electrospinning with a non-rotating collector and followed by a high-temperature sintering process. The effects of PTFE/PEO mass ratio and sintering temperature on the morphologies and properties of the resulting membranes were investigated. The prepared PTFE hollow fiber membrane shows the excellent characteristics combining the advantages of both electrospun nanofibers membrane and hollow fiber membrane, such as high porosity (more than 82%), self-supporting and superhydrophobicity. The membrane sintered at 380 °C present the highest mechanical strength, which shows the tensile strength, Young's modulus, strain at break of 30.5 Mpa, 53 Mpa, and 315%, respectively. The permeate flux of the prepared PTFE hollow fiber membrane is about 4.6–8.8 times as that of the commercial PTFE hollow fiber membranes, as well as is approximately 3.2–11.6 times higher than the date of the reported PTFE hollow fiber membranes. Additionally, the prepared membrane shows high and stable flux in long-term and rising salinity experiments, indicating it is very promising for membrane distillation (MD) application and even for the treatment of hyper-saline wastewater.
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•Novel hollow fiber membranes composed of pure PTFE nanofibers.•Scalable and environment-friendly method was proposed.•Membranes are high porous, self-supporting and superhydrophobic.•3.2–11.6 times higher than the flux of reported PTFE hollow fiber membranes.•Stable and high flux in treatment of hyper-saline wastewater.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•PTFE hollow fiber membrane was fabricated via electrospinning with no organic solvent.•Pullulan was used as the carrier of the PTFE for electrospinning.•The prepared membrane shows high porous, ...superhydrophobicity and high LEP.•The KOE of the prepared membrane is 1.6–2.4 times higher than commercial membrane.
Polytetrafluoroethylene (PTFE) is increasingly used in membrane applications due to its excellent thermal stability, resistance to chemical degradation and strong hydrophobicity. However, it is difficult to prepare high flux membranes by conventional technology due to its high melt viscosity and solvent resistance. Here, a environment-friendly technology is used to fabricate PTFE hollow fiber membrane via emulsion electrospinning. Pullulan is dope into the PTFE emulsion and employ as the binder of PTFE particles to facilitate the formation of the as-spun PTFE-Pullulan hollow fiber membrane. The expected PTFE hollow fiber membrane is obtained after sintering of the as-spun membrane. No organic solvent is used and no pollutant is discharged during the preparation process. The prepared PTFE hollow fiber membrane shows excellent properties such as superhydrophobicity (contact angle > 150°), high porosity (85%) and excellent mechanical properties (Young's modulus of 39 MPa and fracture strain of 245%). In the deamination test, the experimental mass transfer coefficient of the PTFE hollow fiber membrane reaches 2.4*10−5 m/s when the pH is 11, which is 1.6–2.4 times as that of the commercial membrane. The self-made PTFE hollow fiber membrane shows great potential in the application of membrane deamination.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Membrane technology, as one of the key standard technologies for green chemistry and sustainable development, has been applied for a wide range of separation and purification processes. Poly ...(tetrafluoroethylene) (PTFE), known as a combination of excellent properties, have been widely employed in a vast number of membrane process fields for the last several decades, typically in liquid/air separation, biomedicine, and new energy applications et al. This review first provides an introduction to PTFE material, including the polymerization process, structure and properties, processing, recycling and applications. Subsequently, particular emphasis is given to recent progress in the preparation method and technology of PTFE porous membranes. Moreover, the strategies to control membrane pore structure, and the functionalization of PTFE porous membranes are assorted and illustrated in detail. The essential problems connected to the practical applications of PTFE porous membranes are then highlighted. A brief conclusion and perspective of PTFE porous membranes in future research are summarized and prospected in the end. It is hoped that the systematic description of this review will acquaint the readership with a fundamental understanding of PTFE materials, enabling them to choose an appropriate PTFE membrane production technology for a variety of real-world applications. Future PTFE-based membrane technology development may benefit from the knowledge provided by this review.
The comprehensive review provides updates on the recent developments of PTFE porous membranes based on the polymer of PTFE, with significant attempts to improve PTFE porous membranes. Display omitted
•Introduction to structure, properties, processing, recycling and applications of PTFE.•Progress in preparation, structure control, and functionalization of PTFE membrane.•The key issues associated with PTFE porous membranes for actual applications.•A brief conclusion and perspective of PTFE porous membranes in future research.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Tribocatalysis of homogeneous material was revealed for the first time.•Rubbing multi-size PTFE particles can degrade organic pollutants.•The multi-size PTFE tribocatalysis has high ...durability for degradation of pollutants.•Tribocatalytic mechanism of homogeneous material was proposed.•The tribocatalytically degraded pathway of pollutants was studied.
Recently, tribocatalysis driven by mechanical energy has been developed by rubbing two kinds of different materials. In this work, we firstly demonstrated that the friction of the single material also could initiate the tribocatalysis for degrading organic dyes. Under magnetic stirring, the multi-size granular polytetrafluoroethylene (PTFE) particles were triboelectrically charged, among which the collision between large and small particles would cause high energy electrons on large particles to transfer to small ones. These triboelectric charges on PTFE particles could react with adsorbed oxygen molecules or water to generate reactive oxygen species, and then promoted the degradation process of organic dyes together with oxidant holes. We further investigated the experimental parameters, such as stirring speed, size and quantity of stirring bar, to optimize the tribocatalytic performance. What’s more, the PTFE tribocatalysis possessed high durability for multiple recycling runs with > 90% degradation efficiency of Rhodamine B, as well as well universality for eliminating other pollutants. Finally, we proposed a plausible tribocatalytic mechanism of multi-size granular PTFE according to the detected reactive oxygen species and the determined intermediates. This study provides new insights into tribocatalysis, and demonstrates that the single material with different particle sizes can also be used as catalyst to drive tribocatalytic process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The tribological properties of hybrid polytetrafluoroethylene (PTFE)/aramid fibers 1414 (Kevlar) fabric self-lubricating composite under different conditions was studied. To improve tribological ...properties and the bonding performance of PTFE, the hybrid Kevlar/PTFE fabrics were treated by sodium-naphthalene complex liquid. PTFE/Kevlar fabric composite was prepared by phenolic-epoxy (6:4) resin. Tribological properties of the composite, friction coefficient and wear amount, were analyzed using varying loads and speeds on a friction and wear testing machine. Worn surface morphology and transfer film were observed by Scanning electron microscopy (SEM). The results showed that the coefficient of friction decreased with the decrease of load and the increase of rotating speed. In addition, the composites with higher PTFE content showed better lubricating behavior. The friction coefficient of the composites reinforced by modified fabrics were more stable and the PTFE transfer film remains more complete.
•The hybrid PTFE/Kevlar fabric self-lubricating composites were prepared.•The PTFE surface was carbonized by the treatment, while, Physical properties of Kevlar were not affected.•The surface treatment improves the friction coefficient stability and the PTFE transfer film completeness.•Friction coefficient and the amount of wear increases as the speed increases, however, the contrary is the case with increases of the load.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The performance of AC/AC (AC=activated carbon) symmetric capacitors based on two commonly used binders–poly(vinylidene difluoride) (PVDF) and poly(tetrafluoroethylene) (PTFE)–introduced in the ...electrodes at same amount (10 wt%) has been compared in 1 mol·L−1 NaNO3 aqueous electrolyte. For capacitors charged up to 1.6V, the PTFE and PVDF-based carbon electrodes exhibit capacitance values of 116 F·g−1 and 104 F·g−1, respectively. This difference in capacitance is related to the presence of the binder which, in the case of the PVDF-based electrodes, causes a more pronounced reduction of pore volume as compared to the pristine powder. The positive electrode of the AC-PTFE/AC-PTFE cell operates under the thermodynamic potential limit of di-oxygen evolution (in 1 mol·L−1 NaNO3, Eox=0.834V vs. SHE) up to 1.4V voltage, while this limit is reached at a voltage of 1.2V with the AC-PVDF/AC-PVDF cell. This shows that the porosity of the electrode strongly impacts the potential range of the positive electrode. Accelerated ageing performed by potentiostatic floating at 1.6V for 120h shows higher capacitance decrease and internal resistance increase in the case of the AC-PVDF/AC-PVDF cell due to a stronger oxidation of the positive electrode caused by the higher potential reached by this electrode. Hence, these results suggest that the performance of supercapacitors might differ depending on the selected binder, and discussions relating the capacitance performance to the textural parameters of the pristine carbon may be biased by a change of porosity. Therefore, it is highly recommended to take into account the gas adsorption data of the electrodes instead of the original powder.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Taking fluorinated graphene (FG) and polytetrafluorethylene (PTFE) as the typical models, this work aims to clarify the influences of carbon-skeleton structure and CF bond strength on their ...tribological performance and lubrication mechanism under extreme-pressure condition. As oil additives, the load-bearing capacity of PAO-6 increases from 300 N to 600 N with FG and 400 N with PTFE. Compared with the situation with the PTFE sub-microspheres, the wear rate of PAO-6 with FG nanosheets reduces by about 40%. Proved by the apparent difference in tribofilm formation ability of FG and PTFE, it is believed that the higher reactivity of the CF bond and adsorption ability of two-dimensional carbon-skeleton play a crucial role in FG’s excellent tribological performance.
•The honeycomb-like carbon structure of fluorinated graphene intensively improves its thermal stability.•The layered structure of FG exhibits better dispersion stability than the microsphere morphology of PTFE.•Due to its lower CF bond strength, it is easier for FG to from tribofilm over the friction surface than PTFE.•As lubricating oil additive, FG exhibits better extreme pressure and anti-wear properties than PTFE.
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GEOZS, IJS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZAGLJ
In this study, the carbon black/polytetrafluoroethylene (C/PTFE) electrode was prepared under the best conditions, and then it was modified by PTFE and NH4HCO3 to make a PTFE-C/PTFE electrode. ...PTFE-C/PTFE electrode was used to enhance H2O2 in-situ electro-generation and the electro-peroxone process (EPP) treatment of leachate. Various analytical methods results were applied to prove that the PTFE-C/PTFE electrode greatly improved the performance of H2O2 generation and electrode stability. The effects of initial pH, current intensity, ozone flow and Cl− concentration on the removal of NH4+ and chemical oxygen demand (COD) from landfill leachate were studied in the EPP with PTFE-C/PTFE as cathode (MEPP) by one factor at a time (OFAT) method. The initial pH value 7.5, current intensity 300 mA, ozone flow 875 mg/h and Cl− concentration value 4198 mg/L were selected as the best operating parameters. A response surface methodology based on box-behnken design (BBD) was employed to optimize running conditions of the MEPP of leachate. After optimization, Mineralization efficiency of the NH4+ and COD was obtained to be 79.83% and 52.14%, and biochemical oxygen demand (BOD5)/COD ratio increased to 0.38 after 4 h. The removal curves of NH4+ and COD in the MEPP conforms to the zero-order and first-order reaction kinetics, respectively. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) analysis shows that MEPP has a good removal effect on organics in leachate. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were carried out for the cathode sediment, which was mainly magnesium ion silicate precipitation and NaCl.
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•Preparation of C/PTFE electrode under optimum conditions.•PTFE and NH4HCO3 modified C/PTFE electrode has better performance.•PTFE-C/PTFE electrode enhances electro-peroxone process.•The process parameters of leachate treatment were optimized by RSM.•The treatment effect of leachate and cathode sediment were analyze.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report a one-step method for fabricating uniform and hierarchical porous HCNSs directly from raw biomass, in which HCNSs were obtained by just thermal treatment of raw biomass in the presence of ...polytetrafluoroethylene (PTFE). The as-fabricated HCNSs show combined advantages of uniform and hollow spherical architecture, high surface area, abundant accessible/open micropores and reasonable mesopores, so the HCNS-based electrode delivers high electrochemical capacitance.
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Hierarchical porous hollow carbon nanospheres (HCNSs) were fabricated directly from raw biomass via a one-step method, in which HCNSs were obtained by thermal treatment of raw biomass in the presence of polytetrafluoroethylene (PTFE). The HCNSs possess coupling merits of uniformly distributed hollow spherical architectures, and high specific surface area, abundant accessible/open micropores and reasonable mesopores, the HCNS-based electrodes deliver high electrochemical capacitance. The formation mechanisms of pores and hollow core-shell structures were explored thoroughly, it is found that the key to the formation of hollow core-shell structure is the onset-pyrolysis temperature difference between raw biomass and PTFE. Moreover, the content of silica had significant effects on the textures of HCNSs, and HCNS with the largest SSA of 1984 m2/g was obtained. Accordingly, a possible mechanism of HCNSs formation was proposed here, where PTFE acted as the pore creation and nucleation agents and raw biomasses were the primary carbon precursors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reaction energy, mechanical behavior, and impact initiation of three kinds of tungsten (W)–polytetrafluoroethylene (PTFE)–aluminum (Al) composites are investigated. The reaction energy results show ...that, the reaction energy of W–PTFE–Al composites in both oxygen and argon decreases with the mass ratio of W increased from 50% to 80%. Quasi-static compression results show that, the increased mass ratio of W has no obvious influence on the strength of W–PTFE–Al composites. However, the critical failure strain presents obviously decreasing tendency with the increased mass ratio of W. Dynamic compression results show that, the strength enhances with the increased W in W–PTFE–Al. The critical failure strain shows no obvious difference when the W content of W–PTFE–Al increases. Under impact condition, the deflagration time of all the three kinds of W–PTFE–Al composites lasts for about 500μs. The insensitivity to impact loading shows an increasing tendency with the increased W mass ratio. During impact compressive deformation, the PTFE matrix is elongated in nano-fibers, thus significantly increases the reaction activity of W–PTFE–Al composites. The nano-fiber structure is necessary for the reaction of W–PTFE–Al composites. The formation of PTFE nano-fibers must undergo severe plastic deformation, which is responsible for the excellent insensitivity of W–PTFE–Al composites.
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•The effect of W content on the reaction energy of W–PTFE–Al composites in both oxygen and argon were investigated.•The effect of W content on the quasi-static and dynamic compression properties of W–PTFE–Al composites was studied.•The effect of W mass ratio on the impact insensitivity of W–PTFE–Al composites was studied.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
