Polytetrafluoroethylene Content Research Articles

Comprehensive Analysis of Wettability in Waterproofed Gas Diffusion Layers for Polymer Electrolyte Fuel Cells.

In polymer electrolyte fuel cells (PEFCs), the gas diffusion layer (GDL) is crucial for managing the flooding tolerance, which is the ability to remove the water produced during power generation from the assembled cell. However, an improved understanding of the properties of GDLs is required to develop effective waterproofing strategies. This study investigated the influence of the polytetrafluoroethylene (PTFE) content on the pore diameter, porosity, wettability, water saturation, and flooding tolerance of waterproofed carbon papers as cathode GDLs in PEFCs. The addition of minimal PTFE (∼6 wt %) to carbon paper provided external waterproofing, whereas internal waterproofing was achieved at a higher PTFE content (∼13 wt %). However, excessive PTFE (∼37 wt %) led to macropore collapse within the carbon paper, reducing fuel cell performance. Although PTFE addition was expected to improve the flooding tolerance, operando synchrotron X-ray radiography revealed that the water saturation level in carbon paper increased with increasing PTFE content. These findings provide a benchmark for assessing whether GDLs meet the flooding tolerance requirements of PEFCs and may be applicable to waterproofed GDLs in electrochemical devices for water and CO2 electrolysis.

Development of a feasible and scalable manufacturing method for PTFE-based solvent-free lithium-ion battery electrodes

Conventional wet-electrode manufacturing encounters challenges in producing thicker electrodes due to issues related to solvent evaporation. This study introduces a novel method for fabricating solvent-free dry electrodes using polytetrafluoroethylene (PTFE) as a binder, representing a significant advancement in electrode manufacturing processes. By eliminating the use of solvents, this method not only addresses these challenges but also offers a scalable and practical solution for mass production. The process is meticulously structured into sequential unit operations, each specifically tailored for a distinct function, utilizing the distinctive fibrillation properties of PTFE. Intermediate product specifications for each phase are clearly defined, accompanied by a comprehensive analysis of both physical and electrochemical performances. This analysis highlights the influence of varying PTFE contents and properties on the microstructure of the dry electrode. Notably, the study achieves a significant breakthrough with an electrode formulation of NCM811/PTFE/carbon black (CB)/carbon nanotube (CNT) = 96/2.0/1.8/0.2, which demonstrates exceptional discharge rate capability of 80 % at a 0.5 C-rate (5 mA/cm2) under the demanding parameters of 10 mAh/cm2 and 3.8 g/cc. This approach not only enhances the microstructural properties of dry electrodes but also paves the way for environmentally friendly and efficient electrode manufacturing for future energy storage applications.

Pore-scale study of two-phase flow in the gas diffusion layer of proton exchange membrane fuel cells: The impact of polytetrafluoroethylene content and gradient distribution

The polytetrafluoroethylene (PTFE) is commonly used to improve the hydrophobic of the gas diffusion layer (GDL). In this study, impacts of PTFE content and piecewise/linear gradient distributions on the transport behavior of liquid water were numerically studied by using a multiphase lattice Boltzmann method. A two-dimensional microstructure of the GDL was reconstructed by stochastic algorithm. The two-phase flow in the GDLs with PTFE contents of 0, 10, 20, 30 and 40 wt% were evaluated and compared. The liquid water transport process can be greatly affected by the PTFE content and the best water drainage performance was provided by the GDL with PTFE content of 30 wt%. Subsequently, the GDLs with PTFE piecewise/linear gradient distributions were designed and investigated. It was found that the water drainage performance can be further improved when the PTFE content is well distributed. This study can provide guidelines for design of GDL for high performance proton exchange membrane fuel cells.

Modification on Drying Chamber Wall of Spray Dryer Towards Better Yield

Spray drying is a widely used industrial process that converts liquid or slurry feed materials into dry powder or granules and it commonly shrouded with the stickiness problem. This study was carried out by response surface methodology (RSM) to minimize fouling during the spray drying process by optimizing the condition of the drying chamber wall of the spray dryer. The concentration (%) and exposure time (min) of polytetrafluoroethylene (PTFE) were examined as independent variables in order to modify the dryer wall. Responses including flux adhesion weight, product recovery, hygroscopicity, and moisture content of the powder were evaluated. Statistical analysis showed that experimental data were best fitted into a quadratic polynomial model with regression coefficient values greater than 0.75 for all responses. The optimum conditions in reducing fouling were discovered at PTFE concentration of 17.27% and PTFE exposure time of 6 min. These conditions would result in low flux adhesion weight (35.28 mg), high product recovery (39.38%), low hygroscopicity (6.08%) and low moisture content (7.97%). The observed outcomes aligned with the predicted values, affirming the suitability of the model in improving the flowability of the spray drying process.

Enhanced Water Management in Fuel Cell Cathodes by the Application of Superhydrophobic Fluorinated Carbon Microporous Layers

Under high current density operation, the efficiency of polymer electrolyte fuel cells (PEFCs) can dramatically decrease. This is due to water accumulation at the cathode side, preventing oxygen diffusion to the electrocatalyst. As such, effective water management is of vital importance by use of a suitable gas diffusion layer (GDL) and/or microporous layer (MPL). MPLs generally consist of carbon black as the porous electron conducting phase, and polytetrafluoroethylene (PTFE) as a hydrophobic binder. Here, we instead use superhydrophobic fluorinated carbon powder in the MPL as a novel material to decrease the required PTFE content. It is confirmed that the water contact angle of the MPL can be increased from 131° to 151° by using fluorinated carbon. Moreover, the fluorinated carbon MPL shows lower oxygen transport resistance at high humidity. Furthermore, in single fuel cell tests at various temperatures and relative humidity values, the I–V performance is significantly and consistently better than for the conventional MPL. These results confirm that fluorinated carbon is a promising new material for water management in the MPLs of PEFCs.This paper is based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).1. Tailored Wettability in Fluorinated Carbon Nanoparticles Synthesized from Fluorotelomer Alcohols, E. Can, M. Nishihara, K. Sasaki, S. M. Lyth, Applied Surface Science, 157136 (2023)2. Superhydrophobic Fluorinated Carbon Powders for Prevention of Flooding in PEFCs, E. M. Can, A. Mufundirwa, T. Kitahara, M. Nishihara, K. Sasaki, S. M. Lyth, Journal of Power Sources, 548, 232098 (2022)3. Solvothermal Synthesis of Superhydrophobic Hollow Carbon Nanoparticles from Fluorinated Alcohol, S. M. Lyth, W. Ma, J. Liu, T. Daio, K. Sasaki, A. Takahara, and B. Ameduri, Nanoscale, 7, 16087 (2015)

Optimization of hydrophobic additives content in microporous layer for air breathing PEMFC

This study explored the ideal polytetrafluoroethylene (PTFE) content in the microporous layer (MPL) for proton exchange membrane fuel cells (PEMFCs) operating under specific conditions: room temperature, ambient pressure, and no-external humidification. The physical properties of MPL were evaluated through FE-SEM and contact angle measurements, and to understand how these properties affect the performance of MPL under unique operating conditions only dependent on internally generated water, the maximum power density at various PTFE contents was compared and electrochemically investigated. Both 5% and 20% PTFE contents exhibited superior performance, and the optimal PTFE content for passive-type cells was determined through performance and durability evaluations. These findings are expected to enhance fuel cell technology's suitability as a compact, portable power source and offer valuable operational insights.

Droplet flow characteristics on experimentally measured gas diffusion layer surfaces of polymer electrolyte membrane fuel cells

Understanding water droplet flow characteristics on realistic gas diffusion layer (GDL) surfaces is crucial for designing high-performance fuel cells. In this paper, droplet flow characteristics on experimentally measured GDL surfaces with different roughnesses are investigated by a volume of fluid (VOF) method in a gas channel (GC). GDL surface morphologies with different roughnesses are obtained by changing the Polytetrafluoroethylene (PTFE) content in the GDL and measured by a 3-dimensional surface metrology microscope. Results show that a low PTFE content reduces the GDL surface contact angle and increases the surface roughness, thus increasing the water droplet discharge time, spreading area and deformation. As the PTFE content increasing, the GDL surface contact angle increases and the surface roughness decreases, thereby yielding a relatively smooth flow process and short water droplet discharge time. Additionally, the water droplet flow characteristics on smooth GDL surfaces are comparatively examined. We find that even when flowing on a surface with the same contact angle, water droplet flow on rough GDL surfaces tends to yield a longer discharge time, larger spreading area, stronger fluctuations and larger pressure drop than on smooth GDL surfaces, further indicating that the GDL surface roughness exhibits a noteworthy influence on water droplet flow.

Arc Voltage as an Indicator of Nozzle Ablation Degradation in High-voltage CO2 Gas Circuit Breakers

Energy released by electric arc during short-circuit current interruption is mostly absorbed by the surrounding cold gas and partly transferred to the arcing contacts and nozzle. The radiation is the main mode of thermal energy transfer between the electric arc and nozzle surface. Experimental research on the nozzle ablation has been carried out at a model circuit breaker, in which CO2 is filled in the chamber and poly-tetrafluoro-ethylene (PTFE) is used as the nozzle material. It is found that the arc voltage can be as an indicator of nozzle ablation degradation by comparing the voltage at current peak and arc voltage extinction peak. Under 20kA and 35kA peak current interrupting conditions, the voltage at current peak decreases with the number of operations. There are two factors that affect the arc voltage at current peak. One is the size of the arc cross section, and the other is the content of PTFE entering the arc zone, which affects its conductivity.

Superhydrophobic electrospun FPI/PTFE nanofiber membranes for robust vacuum membrane distillation

In this study, we firstly proposed a fluorinated polyimide (FPI) /polytetrafluoroethylene (PTFE) nanofiber membrane for vacuum membrane distillation (VMD) by electrospinning FPI and double eletcrospraying PTFE particles. The resultant FPI /PTFE nanofiber membrane possessed desirable superhydrophobicity (water contact angle (WCA) of 155.3°), anti-wettability and durability due to the rough micro/nano structure of the membrane surface. The surface morphology and chemical composition of obtained FPI nanofiber membranes were characterized by SEM, FTIR, XRD and XPS, and the effects of PTFE content on the VMD performance were investigated. Results showed that the liquid entry pressure (LEP) of FPI/PTFE nanofiber membranes increased significantly after PTFE particles were introduced (LEP of 158 kPa). In the VMD process, the FPI/PTFE nanofiber membrane showed stable MD flux (33.49 L·m2·h−1) and excellent salt rejection (99.96%). Furthermore, the FPI/PTFE nanofiber membrane maintained its favorable performance, resulting in stable MD flux (30.21 L·m2·h−1) and salt rejection (99.96%) after the 120 h continuous long-term operation. It shows a promising future for VMD of FPI/PTFE nanofiber membranes.

Nanocomposites with Optimized Polytetrafluoroethylene Content as a Reinforcement Agent in PA12 and PLA for Material Extrusion Additive Manufacturing.

Herein, polytetrafluoroethylene (PTFE) is evaluated as a reinforcement agent in material extrusion (MEX) additive manufacturing (AM), aiming to develop nanocomposites with enhanced mechanical performance. Loadings up to 4.0 wt.% were introduced as fillers of polylactic acid (PLA) and polyamide 12 (PA12) matrices. Filaments for MEX AM were prepared to produce corresponding 3D-printed samples. For the thorough characterization of the nanocomposites, a series of standardized mechanical tests were followed, along with AFM, TGA, Raman spectroscopy, EDS, and SEM analyses. The results showed an improved mechanical response for filler concentrations between 2.0 and 3.0 wt.%. The enhancement for the PLA/PTFE 2.0 wt.% in the tensile strength reached 21.1% and the modulus of elasticity 25.5%; for the PA12/PTFE 3.0 wt.%, 34.1%, and 41.7%, respectively. For PLA/PTFE 2.0 wt.%, the enhancement in the flexural strength reached 57.6% and the modulus of elasticity 25.5%; for the PA12/PTFE 3.0 wt.%, 14.7%, and 17.2%, respectively. This research enables the ability to deploy PTFE as a reinforcement agent in the PA12 and PLA thermoplastic engineering polymers in the MEX AM process, expanding the potential applications.

Self-lubricating micro-arc oxidized polytetrafluoroethylene composite coating on rivet steel for improve corrosion/wear resistance

To improve contact corrosion between auto parts of magnesium alloy and steel rivets during cold connection, a polytetrafluoroethylene (PTFE)-micro-arc oxidation (MAO) composite coating (PTFE-MAO) was prepared on 10B21 steel in the electrolyte consisting of aluminate and phosphate in this work. PTFE carrying anionic surfactant drills into the discharge channel due to the electrostatic adsorption of anions and cations, which plays a role in plugging holes. It shows that PTFE concentration has a significant effect on phase composition, surface microstructure morphology, and corrosion property of MAO coatings. In particular, for the PTFE concentration of 6 g/L, it greatly improves the coating's corrosion resistant, wear resistance, and hydrophobicity. In addition, glycerol (C3H8O3) with 2 mg/L was added to the electrolyte containing PTFE to obtain a composite coating, the corrosion resistance of which is significantly improved, and the decrease in salt spray corrosion rate is doubled compared to the MAO coating. This approach provides a reference for preparing multifunctional anticorrosion coatings on steel substrates.

Optimization of concentration and exposure time of polytetrafluoroethylene (PTFE) for the development of hydrophobic coating of drying chamber of spray dryer

Modelling was applied using response surface methodology (RSM) and central composite rotatable design (CCRD) in order to establish the optimum conditions for applying PTFE on borosilicate glass to create a hydrophobic surface coating. Two experimental operating conditions of concentration and exposure time of polytetrafluoroethylene (PTFE) were optimized, obtaining high contact angle value, and showed high hydrophobic characteristics for PTFE-coated plate. Multiple linear regression analysis was implemented to develop a second-order polynomial model for the response. Results indicated that the most significant (p<0.05) factors influencing the contact angle value of the PTFE-coated plate were the main effect of concentration of PTFE. When the PTFE concentration increases, the plate’s contact angle also increases. The optimum conditions to maximize the value of contact angle (113.23°) for hydrophobic characteristics were a PTFE concentration of 9.17% and a PTFE exposure time of 6 minutes. The experimental results met what was predicted, indicating the model suitability for hydrophobic conditions optimization for the plate. This research indicated a good optimization of a PTFE solution in developing hydrophobic surface on a PTFE-coated plate.

Freezing characteristics of supercooled water in gas diffusion layer of proton exchange membrane fuel cells

The freezing characteristics of supercooled water in a gas diffusion layer (GDL), which are the bases for the cold start-up of proton exchange membrane fuel cells (PEMFCs), were investigated. An experimental apparatus for noncontact temperature measurement and observation systems was developed. GDL and GDL with a microporous layer (MPL) were prepared, and freezing experiments using a water-containing GDL under various cooling rates were performed with variations in polytetrafluoroethylene (PTFE) content and water saturation. Furthermore, based on the experimental results, the freezing initiation probability was theoretically investigated to elucidate the freezing characteristics. Results showed that, with increasing supercooling of water in GDL, the freezing probability of water increased abruptly. The effect of saturation showed a different trend depending on PTFE addition. For the GDL without PTFE, the freezing initiations occurred at approximately 6 °C of supercooling degree, and the probability approached 1.0 at approximately 9.5–11.5 °C, with saturation dependency. In contrast, for both GDL and GDL + MPL containing PTFE, the initiation temperature characteristics were relatively similar, which were approximately 8–12 °C, regardless of the saturation and PTFE content. In these cases, the ice-nucleating activity of water in the GDL was possibly stronger than that in the MPL.

Effect of Polytetrafluoroethylene (PTFE) Content on the Properties of Ni-Cu-P-PTFE Composite Coatings

Q235B mild steel has the advantages of good mechanical properties, welding properties, and low cost, and it is widely used in bridges, energy fields, and marine equipment. However, Q235B low-carbon steel is prone to serious pitting corrosion in urban water and sea water with high chloride ions (Cl-), which restricts its application and development. Herein, to explore the effects of different concentrations of polytetrafluoroethylene (PTFE) on the physical phase composition, the properties of Ni-Cu-P-PTFE composite coatings were studied. The Ni-Cu-P-PTFE composite coatings with PTFE concentrations of 10 mL/L, 15 mL/L, and 20 mL/L were prepared on the surface of Q235B mild steel by the chemical composite plating method. The surface morphology, elemental content distribution, phase composition, surface roughness, Vickers hardness, corrosion current density, and corrosion potential of the composite coatings were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), three-dimensional profile, Vickers hardness, electrochemical impedance spectroscopy (EIS), and Tafel curve test methods. The electrochemical corrosion results showed that the corrosion current density of the composite coating with a PTFE concentration of 10 mL/L in 3.5 wt% NaCl solution was 7.255 × 10-6 A∙cm-2, and the corrosion voltage was -0.314 V. The corrosion current density of the 10 mL/L composite plating was the lowest, the corrosion voltage positive shift was the highest, and the EIS arc diameter of the 10 mL/L composite plating was also the largest, which indicated that the 10 mL/L composite plating had the best corrosion resistance. Ni-Cu-P-PTFE composite coating significantly enhanced the corrosion resistance of Q235B mild steel in 3.5 wt% NaCl solution. This work provides a feasible strategy for an anti-corrosion design of Q235B mild steel.

Systematic screening of gas diffusion layers for high performance CO2 electrolysis

Certain industrially relevant performance metrics of CO2 electrolyzers have already been approached in recent years. The energy efficiency of CO2 electrolyzers, however, is yet to be improved, and the reasons behind performance fading must be uncovered. The performance of the electrolyzer cells is strongly affected by their components, among which the gas diffusion electrode is one of the most critical elements. To understand which parameters of the gas diffusion layers (GDLs) affect the cell performance the most, we compared commercially available GDLs in the electrochemical reduction of CO2 to CO, under identical, fully controlled experimental conditions. By systematically screening the most frequently used GDLs and their counterparts differing in only one parameter, we tested the influence of the microporous layer, the polytetrafluoroethylene content, the thickness, and the orientation of the carbon fibers of the GDLs. The electrochemical results were correlated to different physical/chemical parameters of the GDLs, such as their hydrophobicity and surface cracking.

Increasing in the heat resistance efficiency of filters using hydrophobic PVA/PEO/PTFE/SA nanofiber and PTFE nanoparticle composite

In this study, a conventional polytetrafluoroethylene (PTFE) foam-coated glass fabric filter (PG) was coated with a nanoparticle (NP)-decorated nanofiber (NF) filter to improve the surface and filtration performance and super water-repellent properties of the baghouse system used in industrial sites. Accordingly, a filter prepared by electrospinning PPPS and electrospraying PTFE NPs (PNP/PNF/PG filter) and a filter without PTFE NPs (PNF/PG filter) were manufactured using 0.005 L/m2 of the NF and a coated PTFE concentration of 0.002 L/m2. The samples were sintered at 320 °C, and a comparative analysis was performed on the samples. The surface of the PNP/PNF/PG filter had a higher surface roughness and contact angle than the PNF/PG filter, confirming that the hydrophobic surface characteristics of the existing PNF/PG filter were improved and maintained. Furthermore, based on the filter performance evaluation, the PNP/PNF/PG filter outperformed the PG and PNF/PG filters. In the particle range of 0.5 to 10.0 µm or more, the efficiency and QF were 98.79 % and 0.006. The PNP/PNF/PG filter improves filter performance while maintaining the surface characteristics of the PNF/PG filter.

Lattice Boltzmann simulation of the structural degradation of a gas diffusion layer for a proton exchange membrane fuel cell

The aging of a gas diffusion layer (GDL) significantly impacts water drainage and mass diffusion within a proton exchange membrane fuel cell (PEMFC). This study employs a stochastic algorithm to reconstruct a 2D microstructure of carbon fiber-type GDL with various different aged degrees. Subsequently, a multiphase lattice Boltzmann method (LBM) is employed to examine water transport within the reconstructed GDLs. Results support the finding that as the GDL ages, its water elimination performance remarkably decreases and much water is retained inside the GDLs. Compared with the degradation of carbon fibers, the degradation of polytetrafluoroethylene (PTFE) leads to a more hydrophilic GDL, thereby reducing the local capillary pressure and forming multipaths for water transport, resulting in a more severe water flooding problem. A proper increase in PTFE content favors GDL antiaging performance, but an excessively high content can occupy pores and reduce the effective porosity, thus reducing the fuel cell performance. These results demonstrate that GDL with a PTFE content of 10 wt% shows better antiaging performance and the highest effective porosity. The study here provides an accurate assessment of liquid water drainage performance of GDL with various different aged degrees and guideline for designing GDLs with high antiaging performance.

Superhydrophobic fluorinated carbon powders for improved water management in hydrogen fuel cells

Under high current density operation, the efficiency of polymer electrolyte fuel cells (PEFCs) can dramatically decrease. This is due to water accumulation at the cathode side, preventing oxygen diffusion to the electrocatalyst. As such, effective water management is of vital importance by use of a suitable gas diffusion layer (GDL) and/or microporous layer (MPL). MPLs generally consist of carbon black as the porous electron conducting phase, and polytetrafluoroethylene (PTFE) as a hydrophobic binder. Here, we instead use superhydrophobic fluorinated carbon powder in the MPL as a novel material to decrease the required PTFE content. It is confirmed that the water contact angle of the MPL can be increased from 131° to 151° by using fluorinated carbon. Moreover, the fluorinated carbon MPL shows lower oxygen transport resistance at high humidity. Furthermore, in single fuel cell tests at various temperatures and relative humidity values, the I–V performance is significantly and consistently better than for the conventional MPL. These results confirm that fluorinated carbon is a promising new material for water management in the MPLs of PEFCs.

Ammonia crossover in thermally regenerative ammonia-based batteries for low-grade waste heat recovery

Ammonia crossover usually occurs in thermally regenerative ammonia-based batteries (TRABs) and significantly deteriorates the performance. In this study, the effect of ammonia crossover on the performance of TRABs and its influencing factors are studied. In addition, an ammonia-breathing thermally regenerative ammonia-based battery with an ammonia gas chamber (ATRB) is constructed by regulating the structure of the gas diffusion layer to control ammonia transfer in the anode. The results show that the cathode performance remarkably decreases with the increase of ammonia content in the cathode, and the amount of ammonia crossover increase with the rise of initial ammonia concentration, discharging current, and temperature. The visualization results show that TRAB with the ammonia diffusion layer can effectively alleviate the ammonia crossover by regulating ammonia transfer. The content of polytetrafluoroethylene (PTFE) in the gas diffusion layer significantly influences ammonia transfer to the porous anode and the cathode. The battery performance increases firstly and decreases later with the PTFE content, and an optimal PTFE content is 20%.

The synergistic effect of polytetrafluoroethylene in-situ fibrillation and dibenzoyl sebacate hydrazide on the crystallization and foaming behavior of poly (lactic acid)

The fully degradable poly (lactic acid) foam with green environmental protection characteristics can alleviate the shortage of petroleum resources caused by the application of plastics. However, due to the inherent low melt strength and slow crystallization rate of linear PLA. It is difficult to obtain PLA microcellular foam with good morphology. In order to obtain PLA microcellular foam with ultra-high expansion ratio and small cell size, PTFE (polytetrafluoroethylene) nanofibers with excellent CO2 adsorption rate were introduced. Self-assembled nucleator TMC-300(dibenzoyl sebacate hydrazide) was also introduced to blend with PLA to obtain small-sized cells. The results show that the PTFE entanglement network as a self-assembled template can effectively improve the early crystallization nucleation efficiency and increase the crystallinity of branched PLA (CBPLA)/TMC by 7 %. The microcellular foam with PTFE content of 0.5 wt% (CBPLA/TMC/PTFE 0.5) was successfully prepared by physical foaming agent, which had the lowest cell size (8.7 μm) And high expansion ratio (1200 %).