Fluorinated Ethylene Propylene Copolymer Research Articles

Research on the Influence of Core Sensing Components on the Performance of Galvanic Dissolved Oxygen Sensors.

The galvanic dissolved oxygen sensor finds widespread applications in multiple critical fields due to its high precision and excellent stability. As its core sensing components, the oxygen-permeable membrane, electrode, and electrolyte significantly impact the sensor's performance. To systematically investigate the comprehensive effects of these core sensing components on the performance of galvanic dissolved oxygen sensors, this study selected six types of oxygen-permeable membranes made from two materials (Perfluoroalkoxy Polymer (PFA) and Fluorinated Ethylene Propylene Copolymer (FEP)) with three thicknesses (0.015 mm, 0.03 mm, and 0.05 mm). Additionally, five concentrations of KCl electrolyte were configured, and four different proportions of lead-tin alloy electrodes were chosen. Single-factor and crossover experiments were conducted using the OxyGuard dissolved oxygen sensor as the experimental platform. The experimental results indicate that under the same membrane thickness conditions, PFA membranes provide a higher output voltage compared to FEP membranes. Moreover, the oxygen permeability of FEP membranes is more significantly affected by temperature. Furthermore, the oxygen permeability of the membrane is inversely proportional to its thickness; the thinner the membrane, the better the oxygen permeability, resulting in a corresponding increase in sensor output voltage. When the membrane thickness is reduced from 0.05 mm to 0.015 mm, the sensor output voltage for PFA and FEP membranes increases by 86% and 74.91%, respectively. However, this study also observed that excessively thin membranes might compromise measurement accuracy. In a saturated, dissolved oxygen environment, the sensor output voltage corresponding to the six oxygen-permeable membranes used in the experiment exhibits a highly linear inverse relationship with temperature (correlation coefficient ≥ 98%). Meanwhile, the lead-tin ratio of the electrode and electrolyte concentration have a relatively minor impact on the sensor output voltage, demonstrating good stability at different temperatures (coefficient of variation ≤ 0.78%). In terms of response time, it is directly proportional to the thickness of the oxygen-permeable membrane, especially for PFA membranes. When the thickness increases from 0.015 mm to 0.05 mm, the response time extends by up to 2033.33%. In contrast, the electrode material and electrolyte concentration have a less significant effect on response time. To further validate the practical value of the experimental results, the best-performing combination of core sensing components from the experiments was selected to construct a new dissolved oxygen sensor. A performance comparison test was conducted between this new sensor and the OxyGuard dissolved oxygen sensor. The results showed that both sensors had the same response time (49 s). However, in an anaerobic environment, the OxyGuard sensor demonstrated slightly higher accuracy by 2.44%. This study not only provides a deep analysis of the combined effects of oxygen-permeable membranes, electrodes, and electrolytes on the performance of galvanic dissolved oxygen sensors but also offers scientific evidence and practical guidance for optimizing sensor design.

A glass-assisting thermally stimulated discharge technique

Thermally stimulated discharge (TSD) technique is a traditional method in dielectric research, especially for electrets. However, in conventional open-circuit and short-circuit TSD techniques, it is difficult to distinguish the surface charge and body charge of dielectric materials. In particular with the test of polymer electrets, the deformation of the polymer film may take place during the measurement process, which will affect the accuracy of the experiment results. In this paper, a glass-assisting TSD (GA-TSD) technique is proposed to solve the above problems. The feasibility of the experimental technique is verified with the GA-TSD spectra of fluorinated ethylene-propylene copolymer electret films. In addition, their theory analysis is also accomplished. The influences of glass thickness, glass dielectric property, and metallizing on the glass on GA-TSD spectra are investigated. The results prove that the GA-TSD spectra can clearly distinguish the difference between surface charge and body charge according to the current direction. The quartz glass with the lowest dielectric constant is best suitable for the GA-TSD technique. The influence of the glass thickness and metallizing on the glass on GA-TSD spectra is little.

Guest Editorial: Polymer electrets and ferroelectrets

Guest Editorial: Polymer electrets and ferroelectrets

Fluorinated ethylene-propylene copolymer thermal degradation with its effect on copolymer physical and structural properties

Fluorinated ethylene-propylene copolymer thermal degradation with its effect on copolymer physical and structural properties

Digital Strategies to Improve Product Quality and Production Efficiency of Fluorinated Polymers: 1. Development of Kinetic Model and Experimental Verification for Fluorinated Ethylene Propylene Copolymerization

Digitalization of industrial polymerization processes represents an effective and efficient approach for product-grade upgrading and for production efficiency improvement. A mechanistic model based on the first principles of elementary reactions and mass balances provides a powerful tool in the practice of process digitalization. In this work, we developed a comprehensive kinetic model for the batch process of bulk copolymerization of tetrafluoroethylene with hexafluoropropylene. A series of experimental runs were carried out under various conditions. The fluorinated ethylene propylene copolymer samples were collected, with the monomer conversions, copolymer compositions, and polymer molecular weights, as well as the melting and crystallization properties, fully analyzed. The model was then correlated with the data for estimation of the model parameters. The reactivity ratios were found to be r1 = 65.5 and r2 = 2.6 × 10–3. With a whole set of estimated parameters, the model was used to simulate results under different polymerization conditions close to industrial production processes, which were further verified with additional experimental data. The agreement between simulated and experimental results was good. The experimentally verified model provides a powerful tool for industrial process optimization aiming at improvement of product quality and production efficiency.

Self-powering vibration sensor based on a cantilever system with a single-electrode mode triboelectric nanogenerator

Here, we report a vibration sensor based on a single-electrode mode triboelectric nanogenerator (TENG). The main objective of this study is to develop a vibration sensor (architecture) that can be employed in any application with minor design changes to meet individual objectives. Hence, a cantilever-based vibration system is selected, which offers optimum design control in fine-tuning the sensor to operate in the desired frequency spectrum. The cantilever’s proof mass is suspended by isotropic linear elastic material constituting a scalable and tunable cantilever–mass system. The oscillations create contact separation between the triboelectric-active layers (i.e. fluorinated ethylene–propylene copolymer and screen-printed zinc oxide), which develop triboelectric waveforms. This voltage waveform is used for both sensing and powering mechanisms. At resonance, the device produces peak-to-peak voltage, short-circuit current, and power density of 25 V, 10 µA, and 1.38 W m−2, respectively. To measure the influence of change in cantilever properties, we varied the number of cantilevers and evaluated the sensor performance. The sensor is reliable with >99% accuracy in a broad frequency range of 0–400 Hz. The sensor exhibits a maximum sensitivity of 14 V g−1 and can charge a 1 µF capacitor to 2.75 V in <150 s. The sensor is further tested on a lab-scale vacuum pump with known (induced) faults to estimate the sensor’s competence in detecting the machinery faults. Considering the market acceptability, the sensor is developed with established manufacturing techniques such as screen-printing, and laser cutting. This study hopes to bridge the lab-to-market gap for TENG-based (vibration) sensors.

Self-powered multifunctional monitoring and analysis system based on dual-triboelectric nanogenerator and chitosan/activated carbon film humidity sensor

A humidity sensor driven by a dual-TENG has been developed for humidity detection at room temperature. In this work, we report a polymer humidity sensor with high response linearity. The sensitive material is made of chitosan (CS) and activated carbon (AC). The sensor is driven by a triboelectric nanogenerator based on fluorinated ethylene propylene copolymer (FEP). The CS/AC humidity sensitive film is coated on a PET substrate with a nickel-chromium alloy interdigitated electrode by spray technique. The peak-to-peak voltage of TENG can be close to 700 V, and the maximum output power is 12.208 mW. The output voltage of TENG is rectified to 48 V to power the humidity sensor, and then we realize that the voltage change range of the humidity sensor is between full voltage of 0–48 V through adjusting the resistance ratio and designing operational amplifier circuit. The sensor has a wide detection range (0%~97% RH) and good stability. Its response/recovery time under 33% RH and 97% RH conditions are 12 s/20 s and 22 s/21 s, respectively. The sensor can realize obvious identification of breathing characteristics in practical application tests. Meanwhile, the sensor can also be used to monitor the distance of the finger from the sensor surface and the response when the water column passes over the sensor surface. In addition, we also sent the signal of the humidity sensor to the smart terminal via WIFI module to monitor the signal changes caused by breathing and finger movement, and matlab was used to analyze the breathing data.

A direct proof for Maxwell–Wagner effect of heterogeneous interface

In this paper, the Maxwell–Wagner effect and the charge characteristics of the heterogeneous interface at the action of higher electric field and elevated temperature are investigated by means of electret technology. A composite membrane with a double-layer structure of a polypropylene (PP) film and a fluorinated ethylene propylene copolymer (FEP) film was made. After being polarized under electric field and elevated temperature, the component PP and FEP films of the composite membranes were separated. The charge density of the PP and FEP films was measured to analyze the characteristics of interfacial charge in the composite membrane. Experimental results directly prove that the charge characteristics at the interface of the composite membranes are consistent with the result calculated by the Maxwell–Wagner effect. The polarity of the interfacial charge can be switched by changing the polarity of the polarizing voltage. The characteristics of the accumulated interfacial charge are strongly dependent on the conductivity, which is affected by the temperature and the polarizing electric field. A new phenomenon, that is, the measured charge density is much higher than that calculated by the Maxwell–Wagner effect, is found. The reason is ascribed to the electret effect from the FEP and PP films. This research provides a new insight into the charge characteristics at the heterogeneous interface.

The Analysis of Light Intensity Transmission Coefficient Through Plastic Fibers for the Design of Closed Room Lighting without Electricity

The phenomenon of total internal reflection can be used to guide the light to be transmitted from one place to another, it is applied to the guiding principle of light in fiber optics. A fiber rope made of clear plastic material with a uniform refractive index, when one end fired a beam of light then the light will be forwarded along the strap so that out at the other end. This principle can be applied as a lighting source in a closed room by passing light from the outdoors by using plastic fiber, so it doesn’t need the electricity. In this study, theoretical analysis of the percentage of the intensity of light transmitted by the fiber plastic succeed as a function of the refractive index and determine the transmission coefficient for some plastic seeds are eligible to be used as a plastic fiber light successor. From the results of deriving the equation, the light transmission coefficient of plastic is and the terms of plastic seeds that can be used as a plastic fiber are having a refractive index . Based on refractive index data from profesionalplastics, the maximum transmission coefficient value for Ethylene Tetrafluoro Ethylene Copolymer is 82.23% and the minimum transmission value of Fluorinated Ethylene Propylene Copolymer is 55.99%.

Foaming behavior of the fluorinated ethylene propylene copolymer assisted with supercritical carbon dioxide

Foaming behavior of the fluorinated ethylene propylene copolymer (FEP) and its composites assisted with supercritical carbon dioxide (scCO2) as the blowing agent were investigated. The batch foaming process was applied at temperature ranging from 250°C to 265°C and pressure ranging between 12 MPa and 24 MPa. The optimal foaming temperature and saturation pressure were obtained for both pure FEP and FEP composites with 1 wt% different-sized BaTiO3 as nucleating agent. The cell diameter of pure FEP foam ranging from 80–140 µm was observed while the cell diameter decreased to 20–40 µm after adding BaTiO3 particles. The cell density of foamed FEP with BaTiO3 increased significantly from 106 to 108 cells/cm3 and the expansion ratio ranged between 4.0 and 5.5. Moreover, a decrease in an abnormal phenomenon that expansion ratio for the pure FEP foam was observed as the saturation pressure increased. This unexpected phenomenon can be explained by the relationship between foaming and crystallization coupling processes.

A conceptual approach to the formation of paramagnetic nanospecies of noble metals

Abstract The general concepts are analyzed regarding the approach for the formation of paramagnetic species of noble metals, with a non-rigid (labile) molecule being used as a supporting matrix. The formation of the metal nanospecies follows three stages: (i) the metal ions are captured by the matrix, (ii) the reducing agent causes formation of individual atoms separated by the matrix fragments, (iii) the individual atoms agglomerate due to conformational transformations of the labile molecule-matrix. This algorithm is realized in two distinct systems: Ag-containing nanospecies embedded within the system of polyacrylic acid (PAA) chains grafted to the film of fluorinated ethylene propylene copolymer (FEP) and Au-containing nanospecies in the free matrix of tannin-citrate- oxo-hydroxo aluminate. The evolution of the electron paramagnetic resonance (EPR) spectra while cooling down demonstrates the appearance of the exchange interaction which is suppressed at higher temperatures by the vibrational modes of the molecule-matrix. The role of the oxo-hydroxo aluminate form is one of a molecular motor sorting the individual nanospecies by their size and charge state.

Space Charge Accumulation Characteristics in Fluorinated Insulating Material under DC High Stress

Electron beam irradiated fluorinated materials, which are used for an OSR (Optical Solar Reflector) of spacecraft have been investigated using a space charge measurement system under DC high stress. It was found that a large amount of space charge accumulated in the electron beam irradiated ethylene-tetrafluoroethylene (ETFE) and fluorinated ethylene-propylene copolymer (FEP) under DC high stress, while it was not observed in non-irradiated them. In this report, a dependence of relaxation time after the irradiation on the space charge accumulation characteristics was also studied.

Photocatalytic antimicrobial films on fluorinated contact lens polymers

Flat TiO2 thin films were dip coated on contact lens polymer substrates (fluorinated ethylene propylene copolymer, FEP) using a hybrid sol-gel and annealed for 12 h at ≤200 °C. The grain sizes were in the range 10–20 nm but extensive shrinkage cracking was present. The crystallinities of the films annealed at ≤150 °C increased with increasing temperature gradually but only to a limited extent, although the crystallinity at 200 °C was significant. Recrystallisation resulted in decreased transparency, increased reflectivity, and a red shift to lower band gap. The methylene blue (MB) degradation was in the order 25 °C < 200 °C < 100 °C < 150 °C, indicating that the photocatalytic performance was dominated by crystallinity and exposed surface area, the latter of which decreased at 200 °C owing to partial submergence in the softened polymeric substrate. The films indicated antimicrobial capacity since they exhibited a maximal level of S. aureus destruction (85%) following 5 h of UV irradiation. The films also appeared to be microstructurally stable following wash testing in contact lens washing solution.

Charging efficiencies and heat resistance in three types of SiO&lt;sub&gt;2&lt;/sub&gt;/Si&lt;sub&gt;3&lt;/sub&gt;N&lt;sub&gt;4&lt;/sub&gt; electrets

Charging efficiencies and heat resistance of three types of silicon dioxide/silicon nitride double-layer electrets were investigated. These electrets were fabricated with SiO2 films deposited from SiH4 via plasma-enhanced chemical vapor deposition (PECVD SiO2) or with tetraethylorthosilicate (TEOS) using PECVD (TEOS SiO2) or were thermally grown SiO2. Electrets with thicker SiO2 films were found to have higher charging efficiencies and heat resistance than those with thinner SiO2 layers. Moreover, the expected lifetimes of the SiO2 electrets were significantly longer than that of a fluorinated ethylene propylene copolymer electret.

Preparation and charge storage property of FEP thin film electret with grid electric field distribution in millimeter scale

Electret has caught wide attention because it can produce a lasting and stable electrostatic field in the application of MEMS devices such as miniwatt electret generator, electret motor, electret sensor, electret transducer, and so on. Of all the above applications, a remarkable feature is that the electrostatic field distribution on electret surface is patterned in millimeter size or even smaller. However, the charge storage performance of electret in miniature size will dramatically get worse in contrast with the macro-electret. Therefore, it is very important to develop an applicable preparing method to maintain the stability of electrostatic field distribution in micro-patterned electret. In this paper, it is reported that a fluorinated ethylene propylene copolymer (FEP) with evaporated aluminum grid electrode a 25 m thickness topped with at a step of 2 or 3 millimeter are successfully prepared to form the electret with well grid distribution of electric field(abbreviated as grid electret) by means of corona charging and thermal charging technology. Effect of grid width and charging temperature on the charge storage performance is studied. After stored for 150 days, the grid distribution of electric field on the FEP surface becomes clear and organized. The potentials of the area covered by aluminum electrode are close to zero, while that of uncovered area still remain high. The potential differences between the covered and uncovered by aluminum electrode area are identical in different charging methods, it is 110 V (electric field 44 kV/cm) for the sample with an electrode width of 2 mm, and 130 V (electric field 52 kV/cm) for the sample with an electrode width of 3 mm. Results also show that the initial surface potentials of the grid electrets prepared by corona charging is higher than that by thermal charging, but the former decays more rapidly. For the same charging method, the narrower the aluminum electrode area can lead to the lower initial surface potential, and the higher charging temperature causes the larger initial surface potential. According to the principle of corona charging and thermal charging technology it is concluded that the difference of charge storage capability between FEP and aluminum can account for the grid distribution of electric field on the FEP surface.

Synthesis of N-Allyloxycarbonyl 3,5-Dihydroxyphenylglycine via Photochemical Wolff Rearrangement—Nucleophilic Addition Sequence in a Micro-Flow Reactor

In this study, two practical and scalable procedures were developed for the synthesis of N-arylacetyl oxazolidinone, which is an intermediate for the preparation of N-allyloxylcarbonyl 3,5-dihydroxyphenylglycine. The key sequence in the developed procedures was a photochemical Wolff rearrangement–nucleophilic addition in a micro-flow reactor. A power-saving, inexpensive, and readily available light source (4-W portable ultraviolet [UV] lamp) along with a fluorinated ethylene propylene copolymer (FEP) tube was employed in the developed procedures. The first-generation procedure afforded the desired N-arylacetyl oxazolidinone in the highest yield. The yield was lower in the second-generation procedure, but it afforded pure N-arylacetyl oxazolidinone without column chromatographic purification. The use of the two parallel channel tube reactors enabled the gram-scale preparation of N-arylacetyl oxazolidinone. N-Allyloxylcarbonyl 3,5-dihydroxyphenylglycine was successfully prepared via the second-generation pr...

Application of Microflow Conditions to Visible Light Photoredox Catalysis

Applications of microflow conditions for visible light photoredox catalysis have successfully been developed. Operationally simple microreactor and FEP (fluorinated ethylene propylene copolymer) tube reactor systems enable significant improvement of several photoredox reactions using different photocatalysts such as [Ru(bpy)(3)](2+) and Eosin Y. Apart from rate acceleration, this approach facilitates previously challenging transformations of nonstabilized intermediates. Additionally, the productivity of the synergistic, catalytic enantioselective photoredox α-alkylation of aldehydes was demonstrated to be increased by 2 orders of magnitude.

Polymer-capped fiber-optic Raman probe for non-invasive Raman spectroscopy

Advances in fiber optic probe design are moving Raman spectroscopy into the clinic, although there remain important practical problems. While much effort has been devoted to minimizing Raman and fluorescence background from fibers, less attention has been given to the need to generate reference Raman signals that can correct for variations in tissue albedo, which is important in quantifying changes in tissue composition. To address this shortcoming, we have developed a fiber optic probe that incorporates a fluorinated ethylene-propylene copolymer (FEP) cap at the end of each excitation fiber. Transmission of laser light through the transparent cap generates a 732 cm(-1) Raman band whose intensity scales linearly with the laser power delivered to the tissue of interest. In our first design, the FEP cap functions as a waveguide with only a small insertion loss (~5%). Laser transmission through 1 mm of the polymer is sufficient to generate a usable reference Raman signal. We show the application of the probe to quantitative non-invasive Raman spectroscopy of animal tissues using rat leg phantoms as models. Ex-vivo Raman spectroscopy of excised rat tibia supports the use of the probe for spectroscopy of various tissues. These results provide proof of principle that the Raman probe can be used in multiple spectroscopic applications.

The use of a micro-cavity discharge array at atmospheric pressure to investigate the spatial modification of polymer surfaces

A micro-cavity discharge array (2500 cavities of 50 µm 2 size) was operated in neon at atmospheric pressure to modify polystyrene (PS), fluorinated ethylene–propylene co-polymer (FEP) and polytetrafluoroethylene (PTFE) polymer surfaces and, with the injection of a polymerisable monomer (acrylic acid), to deposit patterned, thin polymeric coatings. The aim of this study was to investigate the utility of these micro-discharge sources in the surface treatment of polymers and for the patterned deposition of polymeric material. The influence of the driving frequency, treatment time and sample-array distance on polymer surface treatment was investigated. X-ray photoelectron spectroscopy (XPS) was used to explore the surface chemistry of the treated polymer surfaces and of the polymer deposits . It was found that increasing the micro-cavity discharge source driving frequency and/or treatment time and decreasing the sample-array distance all led to a significant decrease in surface energy as determined by water contact angle measurements. For a period of time, post treatment surface hydrophilicity degraded due to the well known “ageing effect” but stabilized after two days. Finally, it was demonstrated that the device could be used for the localized, array sized, deposition of acrylic acid. High resolution XPS analysis of the deposit registered a C 1s spectra typical of poly(acrylic acid) with a prominent peak centred at approximately 289.3 eV indicating a relatively high level retention of the original monomer functionality. These results demonstrate that micro-cavity discharges, operated at or near atmospheric pressure, can be used to both modify and locally deposit polymeric material.

Erosion of FEP Teflon and PMMA by VUV Radiation and Hyperthermal O or Ar Atoms

A combination of beam-surface-scattering, quartz-crystal-microbalance, and surface-recession experiments was conducted to study the effects of various combinations of O atoms [in the O((3)P) ground state], Ar atoms, and vacuum ultraviolet (VUV) light on fluorinated ethylene-propylene copolymer (FEP) Teflon and poly(methyl methacrylate) (PMMA). A laser-breakdown source was used to create hyperthermal beams containing O and O(2) or Ar. A D(2) lamp provided a source of VUV light. O atoms with 4 eV of translational energy or less did not react with a pristine FEP Teflon surface. Volatile O-containing reaction products were observed when the O-atom energy was higher than 4.5 eV, and the signal increased with the O-atom energy. Significant erosion of FEP Teflon ( approximately 20% of Kapton H) was observed when it was exposed to the hyperthermal O/O(2) beam with an average O-atom energy of 5.4 eV. FEP Teflon and PMMA that were exposed to VUV light alone exhibited much less mass loss. Collision-induced dissociation by hyperthermal Ar atoms also caused mass loss, similar in magnitude to that caused by VUV light. There were no observed synergistic effects when VUV light or Ar bombardment was combined with O/O(2) exposure. For both FEP Teflon and PMMA, the erosion yields caused by simultaneous exposure to O/O(2) and either VUV light or Ar atoms could be approximately predicted by adding the erosion yield caused by O/O(2), acting individually, to the erosion yield caused by the individual action of either VUV light or Ar atoms.