Polytetrafluoroethylene Films Research Articles

Detectability of delamination in laminated CFRPs with diverse stacking sequences using eddy current method with T-R pancake coil

A T-R probe composed of two non-coaxial pancake-based coils is used to identify delamination at different depths of laminated CFRPs with diverse stacking sequences. This type of probe is capable of inspecting delamination, since an interactional in-plane currents across the adjacent and non-adjacent layers of CFRPs stacked by different fibers can be induced using pancake-type coil. For optimizing the probe performance, a frequency sweep method is conducted to obtain the appropriate working frequency. To fabricate the imperfect samples containing the delamination-based damage, a tailored Teflon film is inserted into the appointed interfaces of 16-layer CFRPs. The physical mechanism of delamination detection using pancake coil is analyzed by using FE method. After then, a set of ECT experiments for various CFRPs are performed to verify the sensitivity to delamination detected by pancake coil. Correspondingly, both shape and location of the delamination are compared with those obtained from a well-established UT device. Experimental results indicate that the sensitivity to delamination is high at the interface formed by different stacked fibers, but it lacks sensitivity to delamination in unidirectional one due to the same aligned fibers, which are qualitatively consistent with the numerical results. Unexpectedly, delamination at the interfaces between adjacent layers stacked by the same fibers of the other two CFRPs can still be distinguished from the non-damage region, while this phenomenon fails to explain by the numerical analysis. Quantitatively, the visualized damage region agrees with the UT C-scan results.

A Wireless Intelligent Motion Correction System for Skating Monitoring Based on a Triboelectric Nanogenerator

Smart sport and big data have become inextricably linked with new technologies and devices to monitor sport-related information in real time. In this paper, a lightweight, portable and self-powered triboelectric nanogenerator (LPS-TENG) has been developed to monitor the frequency and force of skaters’ pedaling. Friction layers are formed of polytetrafluoroethylene (PTFE) and nylon films. Based on the triboelectric effect, LPS-TENG does not require an external power supply, and it can be used to monitor biomechanical motion independently. Under the conditions of 1 Hz and 17.19 N, the outputting voltage of LPS-TENG is stabilized at 14 V. Wireless data transmission is achieved with the help of the LPS-TENG and AD module. Visual feedback is provided by the upper computer system in the process of processing data. The wireless intelligent motion correction system is composed of an LPS-TENG, an AD module and a back-end computer. It can clearly analyze the changes between different frequencies and forces during skating. Results showed that the signal of tester’s high-frequency and great-force motion, was transmitted to the computer, and its feedback was given after analysis and processing successfully. The system may help coaches develop training methods, means and tactics to increase athletes’ performance and competitive level in athletic sport. The purpose of this study is to provide new ideas for monitoring skaters’ sport techniques, promote the use of force sensors in the monitoring of sport and develop intelligent assistant training systems.

A PET/Graphite‐Based Triboelectric Nanogenerator for Monitoring the Health of Leg Muscles in Football

Recently, self‐powered flexible sensors have shown important application value in sports training. Thus, we design a triboelectric nanogenerator based on PET/Graphite composite film (PG‐TENG) to harvest human motion energy and monitor football player leg muscle health. The polytetrafluoroethylene (PTFE) film and PET/graphite composite film serve as the triboelectric pairs; meanwhile, the PET/Graphite composite film also plays the role of conductive electrode. Moreover, the PET/graphite composite film can be prepared by a simple reverse molding process. According to the results, the instantaneous power density of PG‐TENG can arrive at 5.94 mW/m2 at 130 MΩ. The PG‐TENG can serve as the motion player to monitor the health of football players’ leg muscles and various football sports postures, including the posture of bouncing and dribbling. This research will promote the application of self‐driving sensors in sports monitoring.

Percolative charge transport on electrified surface of polytetrafluoroethylene

The charge transport on the electrically charged surface of polytetrafluoroethylene (PTFE) films in the presence of the adsorption of an electrically conductive phase has been studied. The attenuation of the rate of displacement of the potential drop over the film surface, which limits the area of its expansion, has been found. An estimate has been made for the critical index of the correlation length of a percolation cluster that forms on an electrified PTFE surface at high humidity. It has been experimentally established that the leak of charge from an electrically charged surface is determined by percolation processes. Keywords: percolation, percolation threshold, adsorption, electrization.

Atomistic study of adhesion of PU/PTFE coating on aluminium oxide surface

ABSTRACT The effectiveness of coatings depends upon various factors and adhesion of the coating to a metallic surface is one of them. Polyurethane (PU) and polytetrafluoroethylene (PTFE) are widely used polymeric coatings for the protection of metallic surfaces. The adhesion of PU and PTFE films on the aluminium oxide substrate is investigated by employing MD simulations. The effect of temperature variation on both the polymeric films has been also studied. Results depict that as the temperature increases the adhesion energy of both the polymers increases in the range from 273.15 K to 298 K. However, there is no such applications of these polymeric coatings at higher temperature like 548 K, the interaction energy is also calculated at 548 K to predict the behaviour of these polymers at elevated temperatures. PU was found to be more thermally stable compared to PTFE. Moreover, PU adhesion with the aluminium oxide surface was much greater when compared to PTFE which possibly resulted from the existence of oxygen atoms in PU which are responsible for greater adhesion between polymer and metal surface.

Adhesion Improvement Mechanism of Polytetrafluoroethylene by Heat-assisted Atmospheric Pressure Glow Plasma Treatment

The adhesive strength of polytetrafluoroethylene (PTFE) film increased drastically by heat-assisted plasma treatment and PTFE indicated cohesive failure inside the PTFE. By increasing the temperature, defluorination progressed. The PTFE treated with H2/He had significantly lower adhesive strength than the PTFE treated with only He. The peak assigned to stretching vibration of -CH2- could be observed only in the film treated with H2/He plasma. From above, we concluded the improvement of the adhesive strength requires the formation of dangling bonds and a crosslinked structure on the PTFE surface.

Triboelectric Energy-Harvesting Floor Tile.

The aim of this study was to investigate the real-world electrical parameters that strongly affected the performance of a triboelectric energy-harvesting floor tile design: triboelectric material thickness, cover plate displacement distance or gap width, and cover plate pressing frequency, so that real-world specifications of the harvesting floor tile can be accurately specified. The structure of the designed triboelectric energy harvester, with readily available polytetrafluoroethylene (PTFE) film and aluminum foil, was simple and hence easy to fabricate, and the material cost was low. A square wave was used to simulate the pressing frequency on the test bench's cover plate. The results showed that the voltage and current were proportional to the gap width, and the thinner the triboelectric layer thickness, the higher the output voltage and current. A test bench with a 0.2 mm thick PTFE triboelectric layer generated the highest energy output. In a later experiment, a triboelectric energy-harvesting floor tile (TEHFT) prototype was constructed with 0.1 and 0.2 mm thick PTFE layers. We found that at 2 Hz stepping frequency and 0.1 mm PTFE thickness, the optimal load and cumulative energy of the TEHFT were 0.8 MΩ and 3.81 mJ, respectively, while with 0.2 mm PTFE thickness, these two parameters were 1.1 MΩ and 7.69 mJ, respectively. The TEHFT with 0.2 mm thick PTFE layer was able to illuminate a series of 100 to 150 LEDs, sufficient power to drive small electronics and sensor nodes. This discovery provides important data on the structure, material, and contact surface area of a TEHFT that can be adjusted to suit specific requirements of a special function triboelectric energy harvester.

Silicon-carbide (SiC) nanocrystal as technology and characterization and its applications in photo-stabilizers of Teflon

Polytetrafluoroethylene (PTFE) was mixed with silicon carbide nanoparticles in various quantities to create thin films. Long-term UV light exposure to the PTFE films was used to study the effects of SiC NPs as a photo-stabilizer by assessing changes in weight loss and surface shape. Comparing PTFE films with various SiC NP concentrations to the blank film, very little variation was seen. AFM and optical microscopy were also used to analyze the surface morphology of films. When PTFE films with additives were compared to blank film, there were hard to observe any negative changes brought due to photo-degradation. Additionally, the surfaces appeared more uniformly smooth hence SiC NPs work well as photo-stabilizers to impede photo-degradation, particularly 0.0005 gm weight. Silicon carbide nanoparticles absorb ultraviolet light, bind polymeric chains, scavenge radical moieties, and degrade peroxide residues.

Ultrathin, all-organic, fabric-based ferroelectret loudspeaker for wearable electronics.

All-organic, flexible, and body-compatible loudspeakers have become increasingly attractive for wearable electronics. Due to their remarkable piezoelectric response, ferroelectrets are suitable for loudspeakers. Two distinct kinds ofultrathin ferroelectrets, including cellular polypropylene films and expanded polytetrafluoroethylene (ePTFE) films, were combined with three different types of electrodes ((Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS))-coated fabrics, PEDOT:PSS direct coating, and sputter-coated Au/Pd) for study regarding their frequency-dependent sound intensity and radiation directivity. Among the loudspeakers investigated, the all-fabric loudspeakers with ePTFE ferroelectret and PEDOT:PSS-coated spandex electrodes have a higher frequency dependency. Loudspeakers equipped with PEDOT:PSS-coated spandex electrodes are less angle dependent compared to other loudspeakers evaluated. Moreover, the soft loudspeaker constituted of an all-organic FEP(fluorinated-ethylene-propylene)-ePTFE-based ferroelectret and PEDOT:PSS-coated fabrics presented in this paper is easy to integrate with clothes and has a higher thermal stability. It is naturally compatible with the human body and a competitive candidate for future developments of all-organic loudspeakers for wearable electronic systems.

A Stable and Durable Triboelectric Nanogenerator for Speed Skating Land Training Monitoring

In the current IoT era, the key to sports intelligence is the effective collection and analysis of sports data. Sports data can accurately reflect an athlete’s athletic status and help coaches to develop competitive tactics and training programs. Wearable electronic devices used to collect sports data currently have several drawbacks, including their large size, heavy weight, complex wiring, high cost, and need for frequent power replacement. In this work, transparent polyamide-66 (PA-66) and transparent polytetrafluoroethylene (PTFE) films were used as friction layers, polydimethylsiloxane (PDMS) was used as a support layer, and conductive hydrogels were used as electrodes, which were simply combined to create stable and durable triboelectric nanogenerators (SD-TENG) with good mechanical and triboelectric properties. In the test, the output power was 1mW under a load resistance of 10MΩ. In addition, the integrated intelligent speed skating land training assistance system monitors the changes in the joints and joint chains of skaters during land training in real time. The successful demonstration of the use of SD-TENG in speed skating land training will help to promote the development and application of TENG in the fields of intelligent sport monitoring, smart wearable devices, and big data analysis.

Onion-like carbon as nano-additive for tribological nanogenerators with enhanced output performance and stability

Triboelectric nanogenerators (TENGs) with sliding-mode have developed rapidly in the field of energy harvesting and sensing. However, its surface wear and low electric output performance usually limit its applicability. Herein, a mixture of hexadecane with onion-like carbon (OLC) lubricant is added to the interface between polytetrafluoroethylene (PTFE) film and steel to enhance the triboelectrical and tribological performance. During dry friction, the friction pair is severely worn and the current output decreases gradually with the transfer of a large amount of PTFE debris in a short period. The introduction of hexadecane partly resolves the problems such as friction and wear with the reduction in the transfer of PTFE material. However, the current output decreases gradually during the friction process because there is still some slight material transfer in the interface. The electrical output of TENG is further enhanced with the addition of OLC, and its tribological properties are comparable or better than oil-based TENG. The short-circuit currents (Isc) of the oil-based TENG and the oil-OLC-based TENG are 1.5 times and 5 times that of the TENG in the dry friction state, respectively. Also, the coefficient of friction (COF) of oil-OLC-based TENG is reduced by about 75.3% compared with dry friction state. The oil-OLC-based lubricant reduces the transfer film formation, increases the effective contact area, and squeezes the air at the interface. Also, part of the OLC rolls between the two friction layers, forming a "micro-bearing", further reducing the generation of transfer film. This study provides a novel way to improve the output efficiency and prolong the service life of TENG.

Evaluation of corrosion performance of superhydrophobic PTFE and nanosilica coatings

Corrosion protection of metals is of paramount importance in different sectors of industry. One of the emerging techniques to prevent or reduce the damaging effects of this phenomenon is to apply superhydrophobic coatings on the susceptible surfaces. In this study, corrosion protection of steel is investigated by fabricating superhydrophobic coatings, using one-step electrodeposition process of nanosilica hybrid film and spraying process of polytetrafluoroethylene (PTFE) on steel surface and also preparation of micro/nano-composite coatings. The anti-corrosion behavior of the nanosilica hybrid film and PTFE coating with two types of microparticles including Al2O3 powder and glass beads in primer layer, and overcoat layer with and without SiO2 nanoparticles is studied. TOEFL polarization and electrochemical impedance spectroscopy (EIS) tests are conducted on coated steel samples to examine their corrosion performance in 3.5 wt% NaCl solution at a temperature of 25 °C. The results showed that the combination of superhydrophobic properties and low conductivity significantly improves the corrosion resistance. Evaluating the effect of adding SiO2 nanoparticles to the overcoat layer in PTFE coating showed that the nanoparticles improve the corrosion resistance of PTFE coatings by sealing up some defects and pores in the coating. Investigation of corrosion resistance of coatings showed that, the corrosion resistance of nanosilica film is lower than that of PTFE coatings. The best sample obtained in this study, namely the PTFE coating with glass beads microparticles in primer layer and SiO2 nanoparticles in overcoat layer, reduced the corrosion rate by nearly 80 times.

Delamination detection on composite laminates using the modal displacement unevenness coefficient

This paper develops a new detection method taking the power function of the modal displacement curvature difference as a damage index to accurately identify the location and degree of the delamination. The 4-layer Poly Tetra Fluoro Ethylene films of size 0.02 m × 0.11 m are embedded between adjacent carbon fiber prepregs being 0.06 m and 0.115 m away from the left edge, respectively. The force-hammer excitation experiment is carried out on the prepared laminates with fixed supports at both ends, and the frequency response curves of measuring points are processed by the Polylscf algorithm in Dong-Hua Data Analysis System. The finite element model of delaminated laminates is established through adding new layers with film properties, and the modal displacements of nodes are compared with experimental data. The number of measuring points in the experiment is limited, making the precise characterization of surface abrupt characteristics difficult. The numerical results are used to calculate the square of the Gaussian curvature difference between the modal displacements of intact and damaged laminates. Significant improvement of the delamination detection accuracy is achieved in this process, confirming that the developed method constitutes a valuable tool for the Non-Destructive Testing of the laminates.

A Lightweight Sensitive Triboelectric Nanogenerator Sensor for Monitoring Loop Drive Technology in Table Tennis Training

As the Internet of Things becomes more and more mainstream, sensors are widely used in the field of motion monitoring. In this paper, we propose a lightweight and sensitive triboelectric nanogenerator (LS-TENG) consisting of transparent polytetrafluoroethylene (PTFE) and polyamide (PA) films as triboelectric layers, polydimethylsiloxane (PDMS) as support layer, and copper foil as electrode. LS-TENG can be attached to the joints of the human body, and the mechanical energy generated by human motion is converted into electric energy based on the triboelectric effect, thus realizing self-power supply. LS-TENG can monitor the angle changes in elbow and wrist joints when athletes pull the loop and actively generate the output voltage as a sensing signal, which is convenient for coaches to monitor the quality of athletes’ hitting in real time. In addition, LS-TENG can also be used as a power supply for other wireless electronic devices, which facilitates the construction and transmission of large motion data and opens up a new development direction for the field of motion monitoring.

Enhanced Performance of Triboelectric Nanogenerators and Sensors via Cold Spray Particle Deposition.

In this study, a high-performance triboelectric nanogenerator (TENG) is developed based on cold spray (CS) deposition of composite material layers. Composite layers were fabricated by cold spraying of micron-scale tin (Sn) particles on aluminum (Al) and polytetrafluoroethylene (PTFE) films, which led to improved TENG performance owing to functionalized composite layers as friction layers and electrodes, respectively. As-sprayed tin composite layers not only enhanced the flow of charges by strong adhesion to the target layer but also formed a nano-microstructure on the surface of the layers, thereby increasing the surface area during friction. More importantly, the electricity generation performance was improved more than 6 times as compared to the TENG without CS deposition on it. From parametric studies, the TENG using the cold-sprayed composite layer produced an electrical potential of 1140 V for a simple structure with a 25.4 × 25.4 mm2 contact area. We also optimize the geometry and fabrication process of the TENG to increase the manufacturing efficiency while reducing the processing cost. The resultant sprayed layers and structures exhibited sustainable robustness by showing consistent electrical performance after the mechanical adhesion test. The proposed manufacturing approach is also applicable for processing three-dimensional (3D) complex layers owing to the technological convergence of a cold spray gun attached to a robotic arm, which makes possible to fabricate the 3D TENG. To elaborate, a composite layer having the shape of a 3D ball is produced, and the exercise status of the ball is monitored in real-time. The fabricated 3D ball using the TENG transmitted a distinguishable signal in real-time according to the state of the ball. The proposed TENG sensing system can be utilized as a self-powered sensor without the need of a battery, amplifier, and rectifier. The results of this study can potentially provide insights for the practical material design and fabrication of self-powered TENG systems.

Unveiling the growth mode and structure relaxation of Polytetrafluoroethylene film by radio-frequency magnetron sputtering

Relying on radio-frequency (RF) magnetron sputtering, Polytetrafluoroethylene (PTFE) films with a series of thicknesses in the range from 80 to 2000 nm were prepared on silicon substrates. The surface morphology and roughness of the PTFE films were measured by atomic force microscope (AFM) technology at microscale. Results indicated that the PTFE film grew in an island pattern during sputtering, while the surface roughness of PTFE films was almost invariable throughout the sputtering process. Then the structure relaxation of PTFE film annealed at 100 °C for 15–480 min was investigated. Annealing treatment induced columnar protrusions on the PTFE surface, which was due to the flow and rearrangement of molecules. During annealing duration, the columnar structures could continuously rearrange and decompose, and therefore lowering film thickness from 2000 to 1110 nm with increasing annealing time. Due to molecule flow and redistribution of the annealed film, the columnar structures were formed on the surface, which resulted in the higher roughness. Finally, the effects of film thickness and annealing time on the hydrophobicity were also studied.

Chem-bio interface design for rapid conversion of CO2 to bioplastics in an integrated system

Chem-bio interface design for rapid conversion of CO2 to bioplastics in an integrated system

Insight into the role of debris in the formation of polytetrafluoroethylene film via molecular dynamic simulation of debris adhesion

AbstractIn this paper, the role of debris in the formation of polytetrafluoroethylene (PTFE) film was investigated using the molecular dynamic simulation of debris adhesion. The results indicate that the internal structure of PTFE debris could not be changed easily because of the strong cohesion of PTFE debris. Debris will be adhered on Fe surface by the strong adhesion between Fe surface and debris. With the formation of transfer film, the adhesion between thin debris and Fe surface decreases gradually and will be lower than that of debris and PTFE matrix. The difference of the adhesion between PTFE debris and friction pairs will induce the quite different adsorption behavior of thin debris and thick debris. With the formation of stable transfer film, thin debris tends to be adhered on PTFE matrix and thick debris tends to be adhered on Fe surface. This will reduce the interfacial adhesion of friction pairs. The interactive influence between the adsorption of debris and the evolution of transfer film is beneficial to the decrease of COF and the wear of PTFE.

A low power 50 Hz argon plasma for surface modification of polytetrafluoroethylene

The characteristics of a low power 50 Hz argon plasma for surface treatment of polytetrafluoroethylene (PTFE) film is presented in this article. The current–voltage behavior of the discharge and time-varying intensity of the discharge showed that a DC glow discharge was generated in reversed polarity at every half-cycle. At discharge power between 0.5 and 1 W, the measured electron temperature and density were 2–3 eV and ∼108 cm−3, respectively. The optical emission spectrum of the argon plasma showed presence of some ‘impurity species’ such as OH, N2 and H, which presumably originated from the residual air in the discharge chamber. On exposure of PTFE films to the argon glow plasma at pressure 120 Pa and discharge power 0.5 to 1 W, the water contact angle reduced by 4% to 20% from the original 114° at pristine condition, which confirms improvement of its surface wettability. The increase in wettability was attributed to incorporation of oxygen-containing functional groups on the treated surface and concomitant reduction in fluorine as revealed by the XPS analysis and increase in surface roughness analyzed from the atomic force micrographs. Ageing upon storage in ambient air showed retention of the induced increase in surface wettability.

A Mask-Shaped Respiration Sensor Using Triboelectricity and a Machine Learning Approach toward Smart Sleep Monitoring Systems.

Daily sleep monitoring is limited by the needs for specialized equipment and experts. This study combines a mask-shaped triboelectric nanogenerator (M-TENG) and machine learning for facile daily sleep monitoring without the specialized equipment or experts. The fabricated M-TENG demonstrates its excellent ability to detect respiration, even distinguishing oral and nasal breath. To increase the pressure sensitivity of the M-TENG, the reactive ion etching is conducted with different tilted angles. By investigating each surface morphology of the polytetrafluoroethylene films according to the reactive ion etching with different tilted angles, the tilted angle is optimized with the angle of 60° and the pressure sensitivity is increased by 5.8 times. The M-TENG can also detect changes in the angle of head and snoring. Various sleep stages can be classified by their distinctive electrical outputs, with the aid of a machine learning approach. As a result, a high averaged-classification accuracy of 87.17% is achieved for each sleep stage. Experimental results demonstrate that the proposed combination can be utilized to monitor the sleep stage in order to provide an aid for self-awareness of sleep disorders. Considering these results, the M-TENG and machine learning approach is expected to be utilized as a smart sleep monitoring system in near future.