Polytetrafluoroethylene Films Research Articles

Enhancing polytetrafluoroethylene (PTFE) coated film for food processing: Unveiling surface transformations through oxygenated plasma treatment and parameter optimization using response surface methodology.

Spray drying fruit juice powders poses challenges because sugars and organic acids with low molecular weight and a low glass transition temperature inherently cause stickiness. This study employed a hydrophobic polytetrafluoroethylene (PTFE) film to mimic the surface of the drying chamber wall. The Central Composite Design (CCD) using response surface methodology investigated the impact of power (X1, Watt) and the duration of oxygenated plasma treatment (X2, minutes) on substrate contact angle (°), reflecting surface hydrophobicity. To validate the approach, Morinda citrofolia (MC) juice, augmented with maltodextrins as drying agents, underwent spray drying on the improved PTFE-coated surface. The spray drying process for MC juice was performed at inlet air temperatures of 120, 140, and 160°C, along with Noni juice-to-maltodextrin solids ratios of 4.00, 1.00, and 0.25. The PTFE-coated borosilicate substrate, prepared at a radio frequency (RF) power of 90W for 15 minutes of treatment time, exhibited a porous and spongy microstructure, correlating with superior contact angle performance (171°) compared to untreated borosilicate glass. Optimization data indicated that the PTFE film attained an optimum contact angle of 146.0° with a specific combination of plasma RF operating power (X1 = 74 W) and treatment duration (X2 = 10.0 minutes). RAMAN spectroscopy indicated a structural analysis with an ID/IG ratio of 0.2, while Brunauer-Emmett-Teller (BET) surface area analysis suggested an average particle size of less than 100 nm for all coated films. The process significantly improved the powder's hygroscopicity, resistance to caking, and moisture content of maltodextrin-MC juice. Therefore, the discovery of this modification, which applies oxygen plasma treatment to PTFE-coated substrates, effectively enhances surface hydrophobicity, contact angle, porosity, roughness, and ultimately improves the efficacy and recovery of the spray drying process.

A triboelectric nanogenerator based on CNC/gelatin for running and jumping training monitoring

In this work, we proposed a triboelectric nanogenerator (TENG) based on cellulose nanocrystal (CNC)/gelatin composite film (CG-TENG) to monitor the posture and movements of athletes during jumping training. The triboelectric layers comprise a polytetrafluoroethylene film (which carries a negative charge) and a CNC/gelatin composite film (manifesting a positive charge). The CNC is derived from recycled wasted boxes using the traditional sulfuric acid hydrolysis method and is incorporated into the gelatin film as a nanoscale additive. By utilizing an external load resistance measuring 20 MΩ, it is possible to attain an all-time high instantaneous power of 583 µW. The electrical output of the CG-TENG demonstrates notable stability and endurance, as it maintains a consistent pattern during a duration of more than 30 000 cycles. By capitalizing on sustainable and green materials, the CG-TENG paves the way for innovative sports monitoring solutions, amplifying the potential for human physiological signal tracking.

Optical control of degradation of polytetrafluoroethylene films and its modification under electron irradiation

A method for monitoring the degradation of the optical density in polytetrafluoroethylene films and its modification, a copolymer of tetrafluoroethylene and ethylene, irradiated by electrons with energies of 100 keV and 10 MeV is described. The method is based on measuring the optical density of irradiated films in the photon energy range of 1-6 eV and is confirmed by established «dose-optical absorption» relationships. In particular, using the described method, a completely different nature of the radiation degradation of the optical properties of the two types of films under study was discovered. With an increase in the irradiation dose, «bleaching effect» in the region of 2-5 eV and the appearance of an absorption band at 5.6 eV are observed in polytetrafluoroethylene films. With a similar dose increase, three absorption bands at 4.0, 4.6 and 5.5 eV appear and grow in films of copolymer of tetrafluoroethylene and ethylene. The evidence of the critical role of the optical density of films in the functioning of space technology devices is given.

Performance of delaminated CFRP composite under pure bending using two-dimensional digital image correlation

ABSTRACT Delamination is an interlaminar damage which may be pre-existing in multilayered fibre reinforced polymer composite parts due to manufacturing imperfections or generated by out of plane loading during service life. Its existence leads to significant reduction of structural integrity, strength and stiffness of the material. Hence, to study the effect of induced delamination on the performance of a composite under pure bending, a circular polytetrafluoroethylene (PTFE) film was introduced between the second and third plies of a sixteen layered carbon/epoxy laminate during fabrication. The bending tests were conducted in displacement control mode. The displacements and strains were measured through the thickness of the composite using two-dimensional digital image correlation. The damage modes were captured using CCD camera and the causes were explained. The flexural strength and modulus of composite were 329.74 MPa and 104.58 GPa respectively. The delaminated composite behaved as a single member without any crack within the elastic range. The existence of PTFE drastically reduced flexural stiffness of composite beyond the stress at 75.81% of its ultimate strength. The ± 45º plies offered low mechanical performance against the induced off axis loading. Hence, in these plies fibre breakage was higher. In the portion of PTFE, the strains were higher due to larger outward displacements produced by local buckling.

Triboelectric nanogenerator-embedded intelligent bearing with rolling ball defect diagnosis via signal decomposition and automated machine learning

Smart fault diagnosis of bearings is of great significance due to their extensive applications on various occasions. Recently, self-powered sensing technology based on triboelectric nanogenerators promotes the development of intelligent bearings. However, the effective detection and recognition of the rolling element defects of bearings need to be investigated further. This study proposes a triboelectric sensor-embedded rolling bearing (T-bearing) to monitor the working conditions and conduct the defect diagnosis of rolling balls. The interdigitated copper electrode covered by polytetrafluoroethylene film is attached to the inner surface of the outer ring of a commercial bearing. Such a design not only directly forms the TENG with rolling balls to obtain the contact-sensing signals, but also successfully achieves the diagnosis of rolling ball defects with similar triboelectric signals through a novel analysis and prediction paradigm combining signal decomposition and automated machine learning. Finally, a recognition accuracy of 99.48% with five different conditions of bearing balls is reached, which is extremely superior to the highest accuracy of 78.34% without signal decomposition. Thus, this study provides a new strategy for the defect diagnosis and the intelligent application of triboelectric bearings.

Innovative design: Flexible conductive natural rubber electrode sheets with triboelectric generator activated by wheel rotation

Efficient consumption and clean energy management play a vital role in green energy. To be a part of this effort. Among the materials explored, flexible conductive electrodes utilizing triboelectric phenomena and unique properties of natural rubber composites have demonstrated a great potential for mechanical-to-electrical energy conversion. Fabrication process involves modifying natural rubber latex by incorporating conductive fillers such as carbon black, Ketjen black, and multiwall carbon nanotubes. The modified flexible conductive natural rubber sheets (CNRs) are then characterized for their structural and electrical properties. This structural arrangement significantly reduces the electrical resistance of the NR sheets. The incorporation of the MWCNT fillers leads to an increase in dielectric constant of CNRs. These properties are optimized via a proper design of the conductive natural rubber sheet triboelectric nanogenerator (CNRS-TENG). To enhance charge accumulation, polytetrafluoroethylene (PTFE) film is applied to the bottom surface of the CNRs. The CNRS-TENG are integrated into a wheel rotation generator setup. The output performance of the wheel rotation generator is influenced by the rotational speed as well as the arrangement of phases and segments. This work demonstrates that CNRs can be integrated with flexible electronic and other energy harvesting devices, opening possibilities for multifunctional clean energy solutions.

Robust, breathable, and chemical-resistant polytetrafluoroethylene (PTFE) films achieved by novel in-situ fibrillation strategy for high-performance triboelectric nanogenerators

Robust, breathable, and chemical-resistant polytetrafluoroethylene (PTFE) films achieved by novel in-situ fibrillation strategy for high-performance triboelectric nanogenerators

A multifunctional hydrogel-based strain sensor and triboelectric nanogenerator for running monitoring and energy harvesting

Recently, flexible wearable electronics for human running posture monitoring and human energy harvesting have attracted widespread attention. Hence, we design a mixed type conductive hydrogel based on polyvinyl alcohol, cotton paper, graphite oxide, and MXene, named PCGM hydrogel. Furthermore, the PCGM hydrogel can act as the PCGM-based strain sensor and triboelectric nanogenerator (P-TENG) for running posture monitoring and mechanical energy harvesting. The PCGM-based strain sensor has two sensing linear regions: The pressure sensitivity is 0.0164 kPa−1 in the low pressure region (0–16 kPa), whereas it is 0.002 86 kPa−1 in the high pressure region (16–120 kPa). To achieve comprehensive health monitoring of runners, the PCGM-based strain sensors can be installed on human joints and facial skin to monitor human posture and facial expressions. The PCGM hydrogel can be combined with a polytetrafluoroethylene film to form a P-TENG device for mechanical energy harvesting. The P-TENG maximum output power can reach 135 µW with a 30 MΩ load. The short-circuit current (Isc), open-circuit voltage (Voc), and transfer charge (Qsc) of P-TENG can reach 10.36 µA, 229.85 V, and 49.24 nC, respectively. This research provides an effective approach for human-running motion monitoring by using multifunctional flexible devices.

Determination of scattering and Urbach absorption contributions to the light extinction in PTFE films by using graphical representation technique and numerical solution of the inverse problem

Ellipsometrically obtained spectral dependences of ordinary αxy and extra-ordinary αz extinction/attenuation coefficients within the spectral range λ = 300…980 nm of uniaxially anisotropic polytetrafluoroethylene (PTFE) films were analyzed. We considered the capabilities and specific features of the graphical representation technique for determining the contribution of Rayleigh scattering and Urbach absorption to light attenuation in the spectral range beyond fundamental absorption. It has been shown that the graphical approach enables to estimate these contributions qualitatively, semi-quantitatively or quantitatively, depending on the situation. The conclusions made using the analysis of graphical representation are confirmed by numerical solution of the inverse problem via simulation of the αxy (λ), αz (λ) experimental dependences within the framework of a best-fit procedure. Being based on both of these approaches, we have ascertained that, in the as-prepared PTFE films, the so-called anomalous light scattering (ALS) with the spectral dependence of scattering coefficient αs ≈ as λ–p (p > 4) takes place. Transformation of scattering from ALS to the Rayleigh one with p ≈ 4 due to annealing is accompanied by an increase of Urbach (subband) absorption. Both of these factors cause narrowing the dynamic range of extinction coefficient values. Both scattering and absorption coefficients are higher for the component of light polarized along the normal to the substrate as compared to the component polarized in parallel to it. The relationship between observed behavior of the scattering and absorption coefficients and the film structure has been discussed.

Self‐Adaptive Colored Radiative Cooling by Tuning Visible Spectra

Traditional radiative cooling leads to overcooling in the winter season and increases the total energy consumption of buildings. And, the super white color limits its practical applications. In this work, a bilayer coating consisting of a polydimethylsiloxane (PDMS)@thermochromic dye film as the top layer and a super white polytetrafluoroethylene film as the bottom layer is designed to achieve self‐adaptive colored radiative cooling by tuning visible spectra. The mass ratio of PDMS to the black thermochromic dye is 1: 0.04 to balance the solar heating and radiative cooling performances although the thermal emittance is constant (0.95). The designed black adaptive coating can achieve modulations of visible and solar reflectance from 0.36 to 0.91 and from 0.62 to 0.92, respectively. And its net power can switch from 331 W m−2 at −10 °C for heating to 70 W m−2 at 50 °C for cooling down. In the indoor and outdoor experiments, it is shown that adaptive coatings can achieve heating performance in a cold environment while cooling performance in a hot environment. Further energy consumption calculation indicates that adaptive coatings can save 5%−44% of energy consumption in different climates. Various colors and critical transition temperatures can be regulated by different thermochromic dyes for various scenarios.

Super-Low Friction Electrification Achieved on Polytetrafluoroethylene Films-Based Triboelectric Nanogenerators Lubricated by Graphene-Doped Silicone Oil.

The novel proposal of Wang's triboelectric nanogenerator (TENG) has inspired extensive efforts to explore energy harvesting devices from the living environment for the upcoming low-carbon society. The inevitable friction and wear problems of the tribolayer materials become one of the biggest obstacles for attaining high-performance TENGs. To achieve super-low friction electrification of the TENGs, the tribological and electrical behaviors of the sliding-mode TENGs based on polytetrafluoroethylene (PTFE) films and metallic balls under both dry friction and liquid lubrication conditions were investigated by using a customized testing platform with a ball-on-flat configuration. Most interestingly, a super-low friction coefficient of 0.008 was achieved under graphene-doped silicone oil lubrication. The corresponding wear rate of the PTFE film was drastically decreased to 8.19 × 10-5 mm3/Nm. Simultaneously, the output short-circuit current and open-circuit voltage were enhanced by 6.8 times and 3.0 times, respectively, compared to the dry friction condition. The outstanding triboelectrical performances of the PTFE film when sliding against a steel ball are attributed to the synergistic lubricating effects of the silicone oil and the graphene nanosheets. The current research provides valuable insights into achieving the macro-scale superlubricity of the TENGs in practical industrial applications.

Influence of PTFE-Based Dry Lubricants on Friction and Wear Behavior in Dry Lubricated Steel–Bronze Contact

Abstract In this article, solid lubricants are investigated to examine their tribological performance in a dry lubricated steel–bronze contact. The examined solid lubricants are made of polyamide (PA) and irradiated polytetrafluoroethylene (PTFE), which are chemically bonded by reactive melt extrusion. For the tribological investigations, a block-twin-disc test rig, on the one hand, and a three-disc test rig, on the other hand, were used under ambient conditions, where the solid lubricant for lubricating the steel–bronze contact was released from a block or a disc. Results from the tribological investigations are presented here, showing the friction and wear behavior in a steel–bronze contact depending on the slide-to-roll ratio in the contact between the steel disc and the compound body. Furthermore, surface analytical investigations on the steel and bronze discs were carried out. These studies showed that the chemical bonding of 20 wt% of irradiated PTFE in PA12 improves the wear and friction behavior in steel–bronze contact significantly, due to the buildup of a transfer film of PTFE on the steel surface.

Damage formation and evolution mechanisms in drilling CFRP with prefabricated delamination defects: Simulation and experimentation

Delamination is a common defect in carbon fiber reinforced polymer (CFRP) during the molding process. Accurately understanding the formation and evolution mechanisms of drilling damage in CFRP with delamination defects is helpful for effectively suppressing drilling defects with delamination. In this study, a macro-micro finite element model (FEM) of CFRP with prefabricated delamination defects during drilling is established to simulate and analyze the damage formation and evolution behavior. The circular polytetrafluoroethylene (PTFE) films are employed to simulate the delamination defects in CFRP. These samples with different sizes of prefabricated delamination defects are prepared for the drilling experiments. The results show that the maximum errors of the thrust force and the exit damage factor between the simulation and experiments are 8.75% and 4.2% respectively, indicating good reliability of the simulation model. Under the condition of CFRP with delamination defects, as the size of the delamination defects increases, the maximum thrust force decreases, while the maximum delamination propagation length and exit damage increase. Compared to the case without delamination defects, when the delamination diameter is 7 mm, the delamination propagation percentage and the maximum stress in CFRP increase by 52.17% and 155.4% respectively, and the maximum increment of the exit delamination damage factor is 38%.

Enhancing Adhesion between Polyphenylene Sulfide Fabric and Polytetrafluoroethylene Film for Thermally Stable Air Filtration Membrane

Enhancing Adhesion between Polyphenylene Sulfide Fabric and Polytetrafluoroethylene Film for Thermally Stable Air Filtration Membrane

SERS with Flexible β-CD@AuNP/PTFE Substrates for In Situ Detection and Identification of PAH Residues on Fruit and Vegetable Surfaces Combined with Lightweight Network.

The detection of polycyclic aromatic hydrocarbons (PAHs) on fruit and vegetable surfaces is important for protecting human health and ensuring food safety. In this study, a method for the in situ detection and identification of PAH residues on fruit and vegetable surfaces was developed using surface-enhanced Raman spectroscopy (SERS) based on a flexible substrate and lightweight deep learning network. The flexible SERS substrate was fabricated by assembling β-cyclodextrin-modified gold nanoparticles (β-CD@AuNPs) on polytetrafluoroethylene (PTFE) film coated with perfluorinated liquid (β-CD@AuNP/PTFE). The concentrations of benzo(a)pyrene (BaP), naphthalene (Nap), and pyrene (Pyr) residues on fruit and vegetable surfaces could be detected at 0.25, 0.5, and 0.25 μg/cm2, respectively, and all the relative standard deviations (RSD) were less than 10%, indicating that the β-CD@AuNP/PTFE exhibited high sensitivity and stability. The lightweight network was then used to construct a classification model for identifying various PAH residues. ShuffleNet obtained the best results with accuracies of 100%, 96.61%, and 97.63% for the training, validation, and prediction datasets, respectively. The proposed method realised the in situ detection and identification of various PAH residues on fruit and vegetables with simplicity, celerity, and sensitivity, demonstrating great potential for the rapid, nondestructive analysis of surface contaminant residues in the food-safety field.

Conversion of Dielectric Surface Effect into Volume Effect for High Output Energy.

Improving the output energy and durability of triboelectric nanogenerators (TENGs) remains a considerable challenge for their practical applications. Owing to the interface effect of triboelectrification and electrostatic induction, thinner films with higher dielectric constants yield a higher output; however, they are not durable for practical applications. Herein, the dielectric surface effect is changed into a volume effect by adopting a millimeter-thick dielectric film with an inner porous network structure so that charges can hop in the surface state of the network. Charge migration inside the dielectric film is the key factor affecting the output of the triboelectric nanogenerator (TENG)with a thick film, based on which each working stage follows the energy-maximization principle in the voltage-charge plot. The maximum peak and average power densities of the TENG with polyurethane foam film in 1mm thickness reach 40.9 and 20.7Wm-2 Hz-1 , respectively, under environmental conditions, and the output charge density is 5.14times that of TENGs with a poly(tetrafluoroethylene) film of the same thickness. Superdurability is achieved in the rotary-mode TENGafter 200000 operation cycles. This study identifies the physical mechanism of the thick dielectric film used in TENGs and provides a new approach to promote the output and durability of TENGs.

Understanding Transient Ionic Diode Currents and Impedance Responses for Aquivion-Coated Microholes.

Ionic diode based devices or circuits can be applied, for example, in electroosmotic pumps or in desalination processes. Aquivion ionomer coated asymmetrically over a Teflon film (5 μm thickness) with a laser-drilled microhole (approximately 10 μm diameter) gives a cationic diode with a rectification ratio of typically 10-20 (measured in 0.01 M NaCl with ±0.3 V applied bias). Steady state voltammetry, chronoamperometry, and electrochemical impedance spectroscopy data are employed to characterize the ionic diode performance parameters. Next, a COMSOL 6.0 finite element model is employed to quantitatively assess/compare transient phenomena and to extract mechanistic information by comparison with experimental data. The experimental diode time constant and diode switching process associated with a distorted semicircle (with a typical diode switching frequency of 10 Hz) in the Nyquist plot are reproduced by computer simulation and rationalized in terms of microhole diffusion-migration times. Fundamental understanding and modeling of the ionic diode switching process can be exploited in the rational/optimized design of new improved devices.

Linear and nonlinear guided wave based debonding monitoring in CFRP-reinforced steel structures

When carbon fibre reinforced polymer (CFRP) is employed to reinforce the damaged steel structures, the debonding problem existing at the interfaces between two materials can be fatal for the retrofitted structures. As a result, identifying the debonding from its earliest stage can be helpful, which leaves sufficient time for further maintenance actions. Based on the current research findings, the linear guided wave based detection technique can provide a good measure for identifying the existence of gross damage, but it is not as sensitive as the nonlinear guided wave method when detecting the micro damage. In order to develop an effective way to continuously monitor the debonding growth from its initiation, both linear and nonlinear methods were investigated and compared in terms of debonding evaluation in this paper. A fatigue test was carried out on a CFRP-reinforced steel structure, in which a small piece of Teflon film was artificially inserted, to facilitate the debonding development. The correlation coefficient (CC) as well as the damage index (DI) between the benchmark signals and signals after certain cycles of fatigue test were established using both methods. Furthermore, the probability based imaging method was applied to individually show the possible debonding areas based on the data from each method. The finding demonstrated different damage detection sensitivities between the linear and nonlinear guided wave based methods and verified the feasibility of monitoring the whole debonding process by combining these two methods, namely, the nonlinear method for debonding initiation and linear method for debonding growth monitoring.

Optimization of Device Parameters for Back‐Contact Transparent Conductive Oxide–Less Dye‐Sensitized Solar Cells Fabrication

Transparent conductive oxide–less (TCO‐less) dye‐sensitized solar cell (DSSC) has been constructed and characterized employing mesoporous TiO2‐coated stainless‐steel mesh (S‐S‐mesh or Mesh) as a bendable photoanode and iodine‐based redox electrolyte. Efforts have been directed toward optimizing electronic parameters to enhance the power conversion efficiency (PCE) of TCO‐less DSSC to equalize its TCO‐based DSSC counterpart. It is found that protection of Mesh is essential for increasing the PCE of TCO‐less DSSCs employing iodine electrolyte as assured by suppressed reverse saturation current and better diode factor. The PCE of 5.6% is obtained with TCO‐less DSSC compared with TCO‐based DSSC with PCE of 6.09%. A bit of decrease in PCE with TCO‐less DSSC is due to larger resistance in TiO2/dye/electrolyte as well as within electrolyte as evident by electrochemical impedance spectroscopy (EIS) study owing to the Mesh having perforated holes and larger thickness of electrolyte absorbing sheet of the porous polytetrafluoroethylene film (35 μm) compared to TCO‐based DSSC without any barriers and lower electrolyte layer thickness of 25 μm.

Estimation of the size and location of an artificial weld seam defect based on the actual ultrasonic welding phenomenon for online inspection

A series of research has been conducted to analyze the quality of weld seams by non-destructive testing methods. Research on defect analysis using the actual ultrasonic welding phenomenon has not been addressed yet. To ensure a comprehensive quality evaluation, this research estimates the size and location of artificial weld seam defects by the actual ultrasonic welding phenomenon without conventional inspection systems. The welding parameters (power, pressure force, and speed) were carefully selected to ensure optimal bond strength. A superimposed type of seam was produced longitudinally by PVC-coated hybrid textiles in rough to smooth surface contact for two welding groups, using a welding width of 10 mm with an activated cooling air effect. Artificial defects were introduced across the weld seam at five different locations spaced 50 mm apart using Teflon films of 3 and 5 mm width. The actual weld phenomenon of ultrasonic welding process parameters was determined after the recorded machine parameters were converted. The effect of welding process parameters on the seam quality was also analyzed, comparing the weld seam quality between different welding groups and Teflon widths. Based on the discovered graph of the actual welding phenomenon, the location and extent of artificial weld seam defects were estimated. The artificial weld seam defect with a thickness of 0.059 mm at a width of 3.85 mm was estimated at an interval of 50.77 mm using 275 N welding pressure force and 120 W welding power at 2 m min−1 welding speed for 3 mm Teflon width. The results showed that the estimated values closely align with the actual size and position of defects. Overall, this research contributes to the development of a non-destructive testing approach for detecting weld seam defects in ultrasonic welding, emphasizing the importance of these techniques for online inspection and control of weld seam quality.