Copolymer Of Tetrafluoroethylene Research Articles

Concentration of aqueous hydrogen peroxide solution by pervaporation

Pervaporative separation of corrosive liquids is always challenging in terms of finding a suitable polymeric membrane that can withstand the harsh environment especially when concentrating an aqueous solution of a highly oxidizing liquid such as hydrogen peroxide (H 2O 2). H 2O 2 is one of the most powerful oxidizers known and is a stronger oxidant than chlorine, chlorine dioxide and potassium permanganate; hydroxyl radical ( OH) generated from H 2O 2 has a very high reactivity. The choice of membrane material is potentially limited to fluoro polymers and perfluoro polymers considering membrane stability in such a harsh system. Perfluorodimethyldioxole–tetrafluoroethylene (PDD–TFE) copolymer membranes (CMS-3 and CMS-7) were used to concentrate hydrogen peroxide from its aqueous solutions. The feed solution composition was varied between 4 and ∼40 wt% H 2O 2; the process was studied at 25 °C, 30 °C and 35 °C. CMS-7 displayed a higher flux than CMS-3; a reverse trend was observed for water–H 2O 2 selectivity for the same feed concentration. The highest water–H 2O 2 selectivity of ∼12 was observed in CMS-3 membrane at an H 2O 2 concentration of 43 wt% with a total flux of 6.15 × 10 −3 g/h cm 2; for CMS-7, values of 9.2 and 9.6 × 10 −3 g/h cm 2 were found for water–H 2O 2 selectivity and total flux, respectively, at the same H 2O 2 concentration. The total permeated flux increased with temperature at the cost of selectivity for both membranes. Extended-term behaviors of CMS-3 and CMS-7 membranes studied at 35 wt% H 2O 2 concentration indicated that both are quite stable for tests carried out over periods of 162 and 145 days respectively.

The Performance of Tensile Properties of ETFE Membranes at Different Temperatures

The tensile test specimens of ETFE (ethylene - tetrafluoroethylene copolymer) membrane have been done at 7 temperatures. It is obtained corresponding stress - strain tensile curve, tensile strength and breaking elongation. Through experiments, it is given the tensile curves at different temperatures to determine turning points on the two rigid method, which has been a turning point corresponding to the yield stress and strain; and it is given ETFE calculation of elastic modulus by tensile curve calculate the tangent modulus, secant modulus, elastic modulus of the second and third; through numerical calculation, it is measured the energy performance of ETFE membranes. The results of the experiments provide a theoretical basis of ETFE membrane to study the architecture.

Effect of Ferroelectric Polarization Domain Structure on Electronic Transport Property of Ferroelectric/ZnO Heterostructure

To discuss the effect of the ferroelectric domain structure on the electronic transport property in the channel of a ferroelectric gate thin film transistor, the electrical property of the ferroelectric gate stack structure of an organic ferroelectric copolymer of vinylidenefluoride and tetrafluoroethylene [P(VDF–TeFE)] and ZnO was investigated. Unlike the gate stack structure using a paraelectric layer, ferroelectrics possibly affect the electron transport in the channel through its domain structure. In this study, the Hall-effect measurements were carried out at various polarized states of P(VDF–TeFE). The Hall mobility at poling voltages from 100 to -100 V showed a gradual decrease with decreasing poling voltage, whereas the carrier concentration shows a slight change in the accumulation state. The change in the carrier concentration indicates the formation of the multidomain structure in P(VDF–TeFE). The multidomain structure might be attributed to the electron scattering in the ZnO channel layer.

Tetrafluoroethylene Copolymers with Sulfonyl Fluoride Pendants: Syntheses in Supercritical Carbon Dioxide, Polymerization Behaviors, and Properties

AbstractCopolymerizations of tetrafluoroethylene (TFE) and perfluoro(3,6‐dioxa‐4‐methyl‐7‐octen)sulfonyl fluoride (PSVE) initiated by bis(perfluoro‐2‐n‐propoxypropionyl) peroxide in supercritical carbon dioxide are investigated. The reactivity ratios for TFE (rTFE) and PSVE (rPSVE) are calculated to be 7.85, 0.079 and 7.92, 0.087 according to Fineman–Ross and Kelen–Tudos methods, respectively. The glass transition temperatures of the copolymers increase with increasing in PSVE content. Comparison studies on above copolymers and another fluorinated sample prepared in emulsion show that the copolymers have comparable properties to the fluorinated one, thus offering an economic way to improve the properties of TFE–PSVE copolymers for their applications in diverse fields. magnified image

Copolymerization of tetrafluoroethylene with perfluoro(3,6-dioxa-4-methyl-7-octene)sulfonyl fluoride in a water-emulsion medium

Copolymerization of tetrafluoroethylene with perfluoro(3,6-dioxa-4-methyl-7-octene)sulfonyl fluoride in a water-emulsion medium

Effect of gamma-irradiation on morphology of copolymer of tetrafluoroethylene with hexafluoropropylene as revealed by thermomechanical analysis and radiothermoluminescence

The morphologies of different commercial forms of the copolymer of tetrafluoroethylene with hexafluoropropylene (FEP) were investigated by thermomechanical analysis. Both granules and powders of FEPs have similar morphologies, but different temperatures for phase transitions. Irradiation reduces the crystallinity of the FEPs and results in a transformation from the crystalline to the amorphous form. After heating of various forms of FEP irradiated at 77 K, there are three intense maxima of radiothermoluminescence in the temperature ranges: 150–144, 174–167, and 210–206 K. The nature of the radiothermoluminescence and the phase transitions of the FEPs as a result of gamma—irradiation are discussed.

Crystal Structure Analysis of Ethylene−Tetrafluoroethylene Alternating Copolymer

Crystal structure of ethylene (E)−tetrafluoroethylene (TFE) alternating copolymer of TFE 50 mol % content has been determined on the basis of 2-dimensional X-ray fiber diagram measured for the uniaxially oriented sample. Different from the unit cell parameters reported previously by several researchers, the newly proposed unit cell is of triclinic type with a = 8.46 Å, b = 5.67 Å, c (fiber axis) = 5.00 Å, α = 83.0°, β = 97.0°, and γ = 89.7° and the space group P1̅. Two slightly deflected but essentially planar-zigzag chains are packed in the unit cell with the zigzag planes parallel to the a + b direction. These two chains are connected by a point of symmetry and are packed upward and downward along the chain axis. In contrast to the relatively sharp X-ray equatorial line profile, the first and second layer line profiles are diffuse. At the same time a series of observed meridional 00l reflections are found to show relative intensity different from the regular chain packing structure. These hkl and 00l reflection profiles were found to be quantitatively reproduced by assuming an aggregation of regular domains with the c-axial translational disorder between them.

High-sensitivity EUV Resists based on Tetrafluoroethylene contained Fluoropolymers

There is a growing interest in the fluorinization of resist materials in improving pattern formation efficiency for extreme ultraviolet (EUV) lithography. The increased polymer absorption coefficient obtained through this resist platform is expected to enhance acid production and in effect improve pattern formation efficiency. Our work over the past several years has shown that the main-chain fluorinated base resins realized by the co-polymerization of tetrafluoroethylene (TFE) and norbornene derivatives offer high dissolution rates. Based on this, a EUV resist which was prepared using the fluorinated polymers was investigated. Imaging evaluations, using the small field exposure tool (SFET by Canon / EUVA) with annular (σ outer 0.7 / σ inner 0.3) illumination conditions were performed. Relatively high sensitivity of 6.3mJ⋅cm-2 for half-pitch (hp) 45nm and satisfactory resolution limit of hp 40nm was achieved. At present, line width roughness (LWR) was measured at comparatively large values of more than 8.4nm at hp 45nm. This shows that further material and process optimizations may be necessary to improve its present lithographic capability. However, these initial results have shown the potential of fluorinated-polymer based platform as a possible solution for high sensitivity, high resolution and low LWR EUV resists. In this paper, we report recent results of high sensitivity of 5.1mJ?cm-2 for half-pitch (hp) 40nm, optimization of protecting groups and photo acid generators.

Structural and property changes during uniaxial drawing of ethylene–tetrafluoroethylene copolymer films as analyzed by in-situ X-ray measurements

The structure–property relationship during uniaxial drawing of high-molecular-weight ethylene–tetrafluoroethylene copolymer (ETFE) film was analyzed based on a combination of in-situ wide-angle X-ray diffraction (WAXD) and stress measurements. In-situ WAXD patterns indicated that the hexagonal (100) reflection transformed from the initial un-oriented ring into equatorial spots via split arcs at temperatures both below and above Tg, but that the critical strain when such transition occurred was delayed above Tg. Drawing above Tg produced an equatorial concentration of the spot reflections; thus, the extended chain crystal was enhanced as a result of elongation of the strain-hardening region. In contrast, the draw below Tg remained less oriented even just before breaking. However, the high orientation component also appeared beyond the critical strain; it could be assigned to the so-called “tie molecules” that bind the deformed lamellae. Changes in resultant tensile strength could be interpreted by these extended chain crystals and characteristic tie molecule components.

Long-lived excited state of spiroanthroxazine after its matrix isolation in halogenated polyolefins by supercritical fluid impregnation

Supercritical fluid impregnation was used to perform matrix isolation of spiroanthroxazine (SAO) photochromic molecules in halogenated polymer films (polyvinylchloride and tetrafluoroethylene copolymer with vinylidene fluoride). An excited (colored) SAO form not relaxing to the ground (colorless) state was stabilized in polymers. Such a long-lived excited SAO form could exist as an isomer of the B form (B535 with an absorption band at λmax = 535 nm) in the fluorinated polymer matrix, for which the absorption maximum was shifted by more than 75 nm to the blue, and as the B form with a small admixture of the B535-form (in polyvinylchloride).

Influence of alternating sequential fraction on the melting and glass transition temperatures of ethylene–tetrafluoroethylene copolymer

The melting (Tm) and glass transition (Tg) temperatures of a series of ethylene (E)–tetrafluoroethylene (TFE) copolymer (ETFE) have been found to show unique dependence on the TFE content with the minimal and maximal points. These behaviors have been interpreted successfully on the basis of the degree of alternation of E and TFE monomeric units along the skeletal chain. The melting point of a perfectly alternating copolymer is estimated to be 295 °C on the basis of the dependence of Tm using a modified Flory’s equation. The corresponding Tg was estimated as 145 °C by applying a modified Gibbs–Damnation’s equation.

Study of the Hyflon AD80 perfluorinated copolymer by inverse gas chromatography

The perfluorinated copolymer of tetrafluoroethylene and perfluoromethoxydioxole, Hyflon® AD80x, is investigated by inverse gas chromatography. C5–C13n-alkanes are used as sorbates, for which the specific retention volume, the solubility coefficient at infinite dilution, and the excess thermodynamic functions are calculated in the temperature range 30–115°C. The solubility coefficients of the hydrocarbons in the studied polymer are shown to be lower than those in amorphous Teflons AF1600 and AF2400, a finding that is consistent with the difference between the glass-transition temperatures of these polymers. The correlation between excess partial molar enthalpies and critical volumes of n-alkanes testifies that the upper limit for the size of the free-volume element in this polymer is 613 A3. Mixing of n-alkanes with Hyflon AD80 is thermodynamically disadvantageous (\( \bar G_1^{E,\infty } \) > 0) and becomes even less advantageous with an increase in the size of hydrocarbon molecules. Excess entropy mainly contributes to the high values of excess free energy, thus indicating a higher order in the system containing the glassy polymer than that in systems in which the polymer occurs in the rubberlike state.

Solvent-free nanocomposite proton-conducting membranes composed of cesium salt of phosphotungstic acid doped PVDF–CTFE/PEO blend

In this research, novel nanocomposite membranes were prepared using polymer blend of polyethylene oxide (PEO) and polyvinylidene fluoride–chloro tetrafluoro ethylene (PVDF–CTFE) copolymer with cesium salt of phosphotungstic acid (Cs2.5H0.5PWO40) as proton conductor. Nanocomposite membranes were prepared by solvent-free procedure. The DSC studies show a decrease in crystalinity of polymer matrix with increasing PEO to PVDF–CTFE proportional ratio and the filler. The TGA studies show that membranes are stable up to 180 °C. The TGA also indicates that addition of cesium salt of phosphotungstic acid increases the thermal stability of membranes. The SEMs exhibit that membranes are non-porous and the additive components are homogenously dispersed. Conductivity tests for membranes were carried out in the range of 25–100 °C in dry and hydrated states. Results show that by increasing the temperature, membranes conductivities are increased. In dry state, except at the temperature of 45 °C, membranes which have the highest crystalinity, have the highest conductivity. The alteration of the conductivity in the range of temperatures in dry condition may be attributed to segmental motion of polymer which resulted in proton hopping from one site to another or increasing free volume for proton motion. In fully hydrated state, dynamic equilibrium between different proton moieties determines the mode of proton conductivity which can be described by Grothuss mechanism. In the presence of water molecule, the free proton may be formed. The conductivity for the membrane in hydrated state with the blend ratio of PVDF:PEO = 95:5 w/w and 10% addition of cesium salt of phosphotungstic acid at the temperature of 90 °C is 1.05 × 10−4 S cm−1.

Reduced bleaching in organic nanofibers by bilayer polymer/oxide coating

Para-hexaphenylene (p-6P) molecules exhibit a characteristic photoinduced reaction (bleaching) resulting in a decrease in luminescence intensity upon UV light exposure, which could render the technological use of the nanofibers problematic. In order to investigate the photoinduced reaction in nanofibers, optical bleaching experiments have been performed by irradiating both pristine and coated nanofibers with UV light. Oxide coating materials (SiOx and Al2O3) were applied onto p-6P nanofibers. These treatments caused a reduction in the bleaching reaction but in addition, the nanofiber luminescence spectrum was significantly altered. It was observed that some polymer coatings [a statistical copolymer of tetrafluoroethylene and 2,2-bis-trifluoromethyl-4,5-difluoro-1,3-dioxole, P(TFE-PDD), and poly(methyl methacrylate), PMMA] do not interfere with the luminescence spectrum from the p-6P but are not effective in stopping the bleaching. Bilayer coatings with first a polymer material, which should work as a protection layer to avoid modifications of the p-6P luminescence spectrum, and second an oxide layer used as oxygen blocker were tested and it was found that a particular bilayer polymer/oxide combination results in a significant reduction in bleaching without affecting significantly the emission spectrum from the nanofibers.

Synthesis and performance evaluation of a polymer mesh supported proton exchange membrane for fuel cell applications

Abstract A novel approach to the design and fabrication of proton exchange membrane (PEM) has been developed whereby a non-structural polymer fabricated with high proton exchange capacity was bound to an inert polymer matrix. The patented fabrication techniques used here allow greater flexibility in PEM design. Results related to proton exchange performance of these novel PEMs are presented here. The proton exchange material described herein is a ter-polymer composed of various ratios of monomers. These materials were bound to an inert ethylene–tetrafluoroethylene (ETFE) copolymer mesh that had been rendered adhesive using patented hydroxylation technique in a two-step water-borne process. The basic characteristics of the new membranes were compared to those of Nafion ® 212. An aqueous two-cell testing unit is utilized by which the rate of protons transferred from one cell through the membrane into the other cell was determined by monitoring the change in pH of the cells. Results indicated that the new membrane could transfer protons approximately 10 times faster per unit area compared to Nafion ® 212 under the test conditions utilized at 80 °C. In addition to improvement in induction time and reduced resistance, the new membrane conducts protons at reduced membrane water content compared to Nafion ® 212.

Determination of the content of sulfonyl fluoride groups in the copolymer of tetrafluoroethylene with perfluoro(3,6-dioxa-4-methyl-7-octene)sulfonyl fluoride

The applicability of Fourier IR spectroscopy to determination of the content of sulfonyl fluoride groups in the copolymer of tetrafluoroethylene with perfluoro(3,6-dioxa-4-methyl-7-octene)sulfonyl fluoride (F-4SF copolymer) was examined. A procedure was suggested for determination of sulfonyl fluoride groups, based on a correlation between the analytical signals in the IR absorption spectrum of F-4SF and the sulfur content in F-4SF samples.

Clipped Random Wave Morphologies and the Analysis of the SAXS of an Ionomer Formed by Copolymerization of Tetrafluoroethylene and CF2═CFO(CF2)4SO3H

Using SAXS data, the microstructure of the ionomer formed by copolymerization of tetrafluoroethylene and CF2═CFO(CF2)4SO3H films has been approached by two methods: a numerical method (the unified ...

Kinetics of interaction of tungsten metal with a fluoropolymer

The kinetics of the interaction of tungsten metal with a copolymer of tetrafluoroethylene and vinylidene difluoride (TFE–VDF) has been studied by mass spectrometry (MS), thermogravimetry (TG), and differential scanning calorimetry (DSC). Measurements were taken in a vacuum (MS) and in a dynamic argon atmosphere (DSC, TG) in temperature ranges of 550–585 K (MS) and 313–873 K (TG, DSC). The interaction of tungsten with the fluoropolymer is at least a two-stage process. Its kinetics is described by the Prout–Tompkins nth-order autocatalytic equation. It follows from the kinetic dependences and parameters obtained that the rate-limiting stage of the overall process is the formation of the highest tungsten fluoride WF 6.

Influence of the monomer sequential distribution on the mechanical properties and temperature dependence of an ethylene–tetrafluoroethylene copolymer in association with the phase‐transition behavior

AbstractThe temperature dependence of the mechanical properties of a series of ethylene–tetrafluoroethylene copolymers was interpreted reasonably on the basis of experimental information about the crystalline phase transition and the amorphous‐glass transition behaviors. The crystalline phase‐transition temperature, the glass‐transition temperature, and the bulk modulus were found to depend sensitively on the tetrafluoroethylene content. The magnitude of change in the bulk modulus at the crystalline phase‐transition temperature and glass‐transition temperature was also found to depend sensitively on the tetrafluoroethylene content. These experimental data were interpreted from various levels, including the distribution of the sequential ratios of ethylene–ethylene, tetrafluoroethylene–tetrafluoroethylene, and ethylene–tetrafluoroethylene segments in the copolymer chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Analysis of Pentacene Field-Effect Transistor with a Ferroelectric P(VDF–TeFE) Gate Insulator as an Element of Maxwell–Wagner Effect System

Analysis of pentacene field-effect transistors (FETs) with a ferroelectric gate insulator, i.e., a copolymer of vinylidene fluoride and tetrafluoroethylene [P(VDF–TeFE)], as an element of Maxwell–Wagner system revealed that the turnover of spontaneous polarization in P(VDF–TeFE) modulated the amount of charge injected from the source electrode and accumulated in the FET channel. This analysis well accounted for the hysteresis behavior observed in the Ids–Vgs characteristics. Pentacene FETs using polyimide gate insulator also showed a similar hysteresis behavior in the Ids–Vgs characteristics, but that the results were caused by carrier injection from the gate electrode into the polyimide gate insulator.