Copolymer Of Tetrafluoroethylene Research Articles

Piezoelectric and Dielectric Electrospun Fluoropolymer Membranes for Oral Mucosa Regeneration: A Comparative Study.

Wound healing of the oral mucosa is an urgent problem in modern dental surgical practice. This research article presents and compares the findings of the investigations of the structural, physicochemical, and biological characteristics of two types of polymeric membranes used for the regeneration of oral mucosa. The membranes were prepared from poly(tetrafluoroethylene) (PTFE) and a copolymer of vinylidene fluoride and tetrafluoroethylene (VDF-TeFE) and analyzed via scanning electron microscopy, atomic force microscopy, X-ray diffraction analysis, and Fourier transform infrared spectroscopy. Investigation results obtained indicate that both types of membranes are composed of thin fibers: (0.57 ± 0.25) μm for PTFE membranes and (0.43 ± 0.14) μm for VDF-TeFE membranes. Moreover, the fibers of VDF-TeFE membranes exhibit distinct piezoelectric properties, which are confirmed by piezoresponse force microscopy and X-ray diffraction. Both types of membranes are hydrophobic: (139.7 ± 2.5)° for PTFE membranes and (133.5 ± 2.0)° for VDF-TeFE membranes. In vitro assays verify that both membrane types did not affect the growth and division of mice fibroblasts of the 3T3-L1 cell line, with a cell viability in the range of 88-101%. Finally, in vivo comparative experiments carried out using Wistar rats demonstrate that the piezoelectric VDF-TeFE membranes have a high ability to regenerate oral mucosa.

Determination of optimal technological parameters of fluoropolymer briquetting

The paper discusses the fundamentals of processing fluoropolymers into products and outlines the main operations carried out at each individual technological stage of their processing. It is proven that the preparatory stage of processing fluoropolymers into products significantly affects the quality of the resulting products and their cost. To establish the maximum pressure during briquetting, a granulometric analysis of press powders of polytetrafluoroethylene, copolymer of tetrafluoroethylene with ethylene, and polyvinylidene fluoride was conducted. According to the research results, the main particle size of polytetrafluoroethylene is 20–30 m, for the copolymer of tetrafluoroethylene with ethylene it is 2 m, and for polyvinylidene fluoride it is 5–10 m. This indicates that these polymers should briquette well at relatively low pressures up to 50 MPa. The optimal technological parameters for briquetting press powders such as pressure and holding time under pressure were determined. Their influence on the strength properties of briquetted materials based on fluoropolymers is discussed. It was determined that for the investigated press powders based on fluoropolymers, the optimal briquetting pressure and holding time under pressure are 25–30 MPa and 60–90 s, respectively.

Effect of Gamma Radiation Dose on the Crystal Structure of the Ethylene–Tetrafluoroethylene Copolymer

Effect of Gamma Radiation Dose on the Crystal Structure of the Ethylene–Tetrafluoroethylene Copolymer

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.

Gas Transport Properties of Vinylidene Fluoride-Tetrafluoroethylene Copolymers

The influence of the content of tetrafluoroethylene (TFE) groups on the gas transport properties of vinylidene fluoride (VDF) and tetrafluoroethylene copolymers has been studied. Experimental values of the permeability coefficients P and diffusion coefficients D for gases H2, He, N2, O2, CO2, as well as lower hydrocarbons CH4, C2H4 and C2H6 were measured and their solubility coefficients S were calculated. The values of the solubility coefficients of CO2 and C2H4 were found to deviate from the linear correlation of lg S on the Lennard-Jones potential. An explanation of this effect was proposed based on facilitated transport models. It was demonstrated that an increase in the content of TFE groups leads to a significant increase in the permeability coefficients of the penetrants studied mainly due to an increase in their diffusion coefficients. So, the permeability coefficient of helium and hydrogen increases approximately in 2.5 times, for carbon dioxide in 3 times, for argon, oxygen, methane and ethylene in 3.5 times, and for nitrogen and ethane in 4.4 times, respectively. These gas separation parameters in combination with good film-forming properties and commercial availability allows us to consider the studied VDF-TFE copolymers as promising materials for the fabrication of composite gas separation membranes.

Study of acoustic transmission losses in particle-reinforced rubber-based membrane-type acoustic metamaterials

In this work, the mechanical properties of particle reinforced ethylene propylene diene monomer (EPDM)/ethylene tetrafluoroethylene (ETFE) copolymer material were determined by molecular dynamics (MD) method, and the copolymer material was used in the structural design of acoustic metamaterials. Secondly, based on the discrete point matching method, the acoustic transmission loss characteristics of the material are predicted, and the accuracy and effectiveness of the theory are verified through the multi physical field coupling finite element model. Finally, seven key parameters that affect the material structure are studied, and their influencing rules and mechanisms are analyzed. The results show that the structure makes up for the sound insulation defect of traditional ETFE film materials at low frequencies. Through reasonable selection of key parameters, high sound insulation design can be carried out for specific frequency bands, which is of great significance to the potential application in the construction field (new building materials).

Effect of Orientation Stretching Rate on Piezoelectric Properties in Corona Electrets Based on Vinylidene Fluoride--Tetrafluoroethylene Copolymer

In this paper, the effect of the orientational stretching rate on the piezoelectric properties and structure of the vinylidene fluoride-tetrafluoroethylene P(VDF-TFE) copolymer was studied. A relationship in the formation of the electret and piezoelectric states in P(VDF-TFE) has been established. The parameters of electrically active defects involved in the polarization process and determining the stability of the electret and, as a consequence, the piezoelectric states in P(VDF-TFE) are calculated. Keywords: electret state, polyvinylidene fluoride, tetrafluoroethylene, piezoelectric effect, thermal activation spectroscopy.

Segregated Structure Copolymer of Vinylidene Fluoride and Tetrafluoroethylene Composites Filled with rGO, SWCNTs and Their Mixtures.

This work is devoted to the formation and study of polymer composites with a segregated structure filled with single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO), and their mixtures. For the first time, polymer composites with a segregated structure filled with rGO/SWCNTs mixtures were obtained. A copolymer of vinylidene fluoride and tetrafluoroethylene (P(VDF-TFE)) was used as a polymer matrix. At a fixed value of the total mass fraction of carbon nanofillers (0.5, 1, and 1.5 wt%), the rGO/SWCNTs ratio was varied. The composites were examined using scanning electron microscopy, wide-range dielectric spectroscopy, and tested for the compression. The effect of the rGO/SWCNTs ratio on the electrical conductivity and mechanical properties of the composites was evaluated. It was shown that, with a decrease in the rGO/SWCNTs ratio, the electrical conductivity increased and reached the maximum at the 1 wt% filling, regardless of the samples’ composition. The maximum value of electrical conductivity from the entire data set was 12.2 S/m. The maximum of elastic modulus was 378.7 ± 3.5 MPa for the sample with 1 wt% SWCNTs, which is 14% higher than the P(VDF-TFE) elastic modulus. The composite filled with a mixture of 0.5 wt% rGO and 0.5 wt% SWCNTs reflected 70% of the electromagnetic wave energy from the front boundary, which is 14% and 50% more than for composites with 1 wt% SWCNTs and with 1 wt% rGO, respectively. The lowest transmission coefficient of ultra-high frequencies waves was obtained for a composite sample with a mixture of 0.5 wt% rGO and 0.5 wt% SWCNTs and amounted to less than 1% for a 2 mm thickness sample.

Proton-conducting membranes based on CsH2PO4 and copolymer of tetrafluoroethylene with vinylidene fluoride

In this work, proton conductivity, morphology and mechanical properties of (1–x)CsH2PO4–xF-42 (x=0.05–0.3, weight ratio) membranes were investigated for the first time. Thin flexible membranes for x≥0.15 with the uniform distribution of the components were obtained by a tape casting method. Mechanical properties of the membranes were measured by Vickers microhardness tests for a low polymer content (x˂0.15), also the tensile strength for membranes with high polymer content x=0.2–0.3 were evaluated. Proton conductivity of the (1–x)CsH2PO4–xpF-42 composite polymer electrolytes decreases monotonically with increasing x due to the effect of a «conductor-insulator» percolation. The combination of conductivity, mechanical strength and hydrophobic properties of (1–x)CsH2PO4–xF-42 makes certain compositions of proton-conducting membranes (x~0.2–0.25) promising for their use in intermediate-temperature fuel cells, despite decreased conductivity.

2,2‐Bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene copolymers with different compositions: Synthesis, chain and condensed matter structures and optical properties

AbstractSynthesis of 2,2‐bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene (PDD‐TFE) copolymers with precise chemical structures and understanding effects of the structures on properties are essential for their application. Herein, PDD‐TFE copolymers with different average compositions and narrow composition distributions (NCDs) were synthesized and applied to study the influences of chemical structures on condensed matter structures and optical properties of copolymers. The average length of (PTFE)n sequences were decreased from 7.62 to 1.63, and percentage of TFE in long (PTFE)n sequences (n > 5) decreased from approximately 50% to less than 1%, as PDD molar fraction in the copolymer (FPDD) increased from 13.24% to 52.22%. Consequently, the copolymer with FPDD = 13.24% was semi‐crystalline with a crystallinity degree of 11.57% (determined by WAXD), while the copolymer with FPDD = 52.22% was completely amorphous. The steric energies, glass transition temperatures and transparency of PDD‐TFE copolymers were increased as more cyclic and non‐coplanar structure PDD monomer was incorporated into the copolymers. Refractive indexes of PDD‐TFE copolymers were low and linearly decreased with the increase of FPDD. PDD‐TFE copolymers with high transparencies, low refractive indexes and other excellent properties can be successfully used in the optical fibers and semiconductor fields.

Ultra-low friction, superhydrophobic, plasma micro-nanotextured fluorinated ethylene propylene (FEP) surfaces

Fluorine-containing polymers have attracted a lot of interest due to their hydrophobic nature, which enables a number of functionalities such as low friction, self-cleaning, anti-sticking, etc. Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. In contrast to polytetrafluoroethylene (PTFE), FEP is melt-processable using injection molding and it is highly transparent and resistant to sunlight. Here, we transform fluorinated ethylene propylene ( FEP) surfaces to superhydrophobic using plasma processing (i.e. plasma etching with simultaneous micro-nanotexturing followed by plasma deposition). Two different plasma reactors (an inductively coupled reactor and a reactive ion etcher) and different etching conditions are used in order to micro-nanotexture FEP surfaces. Superhydrophobicity is achieved after plasma deposition of a thin (30 nm) fluorocarbon coating. Subsequently, we probe their frictional properties against water drops using a tilting stage. In particular, we demonstrate wetting control of FEP surfaces with water static water contact angle ranging from 95 o to 168 o and hysteresis down to 1–2 o . Video analysis of drops moving on different FEP surfaces shows that water drops exhibit reduced friction as etching time increases so that a hierarchical morphology is created. This is achieved using both plasma reactors, whereas the optimum performance is observed for the 10 min etched surface in a inductively coupled plasma reactor in which friction force becomes 0.7–1 μN, which corresponds to an ultra-low dynamic coefficient of friction (at least one order of magnitude lower to that of untreated FEP). • Plasma Processing for wetting control of FEP surfaces. • Superhydrophobic FEP surfaces are demonstrated. • Water drops move with reduced friction on SH FEP surfaces. • Coefficient of friction is reduced to 0.007 for SH FEP surfaces.

Effect of Aging on the Mechanical Properties of Highly Transparent Fluoropolymers for the Conservation of Archaeological Sites.

In recent years, fluoropolymers have found numerous applications in the architectural field because of their combination of mechanical-chemical resistance and high transparency. In the present work, commercial fluorinated polymers, such as perfluoro alkoxy (PFA) and ethylene tetrafluoroethylene copolymer (ETFE), have been evaluated for use as protective and transparent layers on monumental and archaeological sites (to preserve mosaics or frescoes) during the phases of restoration or maintenance outdoors. Considering this specific application, the present study was developed by evaluating the evolution of the mechanical (tensile, tear propagation resistance, and low-velocity impact tests) and chemical (FTIR and DSC analysis) properties of the films after accelerated UV aging. The results that were obtained demonstrated the high resistance capacity of the ETFE, which exhibits considerably higher elastic modulus and critical tear energy values than PFA films (1075.38 MPa and 131.70 N/mm for ETFE; 625.48 MPa and 59.06 N/mm for PFA). After aging, the samples exhibited only a slight reduction of about 5% in the elastic modulus for both polymers and 10% in the critical tear energy values for PFA. Furthermore, the differences in impact resistance after aging were limited for both polymers; however, the ETFE film showed higher peak force than the PFA films (82.95 N and 42.22 N, respectively). The results obtained demonstrated the high resistance capacity of ETFE films, making them the most suitable candidate for the considered application.

INNOVATIVE POLYMER MATERIALS - IDENTIFYING THE PROBLEM IN A SOCIOLOGICAL SURVEY

The use of innovative building materials is a topical issue in modem construction. A sociological survey was conducted on the objectives of the study. The use of ETFE films is based both on the possibility of implementing almost any ideas of designers and architects in the design of facades and roofs of various structures, and on the specific features of this fluoropolymer. The characteristics are presented and the advantages of this polymeric material are substantiated. Innovation in construction is an innovation that provides a qualitative increase in the efficiency of the processes of erection or operation of buildings and structures. The construction membrane technology based on the use of a composite polymer material-ETFE film (ETFE - ethylene tetrafluoroethylene or ETFE - ethylene tetrafluoroethylene, or partially fluorinated copolymer of ethylene and tetrafluoroethylene) has a set of advantages compared to traditional technologies. The use of innovative building materials is a topical issue in modem construction. A sociological survey was conducted on the objectives of the study. The use of ETFE films is based both on the possibility of implementing almost any ideas of designers and architects in the design of facades and roofs of various structures, and on the specific features of this fluoropolymer. The characteristics are presented and the advantages of this polymeric material are substantiated. Innovation in construction is an innovation that provides a qualitative increase in the efficiency of the processes of erection or operation of buildings and structures. The construction membrane technology based on the use of a composite polymer material-ETFE film (ETFE - ethylene tetrafluoroethylene or ETFE - ethylene tetrafluoroethylene, or partially fluorinated copolymer of ethylene and tetrafluoroethylene) has a set of advantages compared to traditional technologies.

Influences of inner surface of pipe on deposit formation

Engine deposits in exhaust gas passages cause the increase of the pumping loss and the failing of the valve action. Deposits also affect EGR gas temperature in cooled EGR system because their thermal conductivity is low. Therefore, it is necessary to reduce engine deposits in order to improve engine performance. In this study, the influences of the inner surfaces of pipe on deposit formation are investigated by comparing the deposition on SUS304 and two kinds of fluorocarbon polymer, PTFE(polytetrafluoroethylene) and PFA(copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether). Deposits are experimentally formed by smoke produced when diesel fuel is burning in an alcohol lamp or actual exhaust gas emitted from a gasoline engine. The results indicate that different surfaces make difference to the amount and shape of deposits. In addition, it is suggested that small Van der waals force and non-wettability contribute to deposit reduction.

One-step production of 3D printed ferroelectric polymer forms using fused deposition modeling

This Letter presents the possibility of 3D print polymer forms with a ferroelectric crystal structure in a one-step process by using the fused deposition modeling method. The approach does not require any additional equipment, other than an extruder for filament production and a commercial 3D printer to fabricate ferroelectric polymer forms. By using the copolymer of vinylidene fluoride and tetrafluoroethylene as a filament for 3D printing, complex spatial structures, such as the gyroid form, are accessible. Compared to polyvinylidene fluoride, the copolymer of vinylidene fluoride and tetrafluoroethylene retains its ferroelectric properties even after melting in the 3D printing process and soldification. The x-ray diffraction investigation shows that the 3D forms are having a planar zigzag conformation on macromolecule scales, which relates to a crystal structure with ferroelectric properties. Annealing the 3D forms at a temperature of 110 °C for 12 h does not cause any changes to the spatial polymer structures but leads to an increase in the degree of crystallinity by more than 20%. This result contributes to an increase in the ferroelectric crystalline phase content by ∼17% and the Curie temperature by ∼7 °C in contrast to non-annealed 3D forms.

Tribological, Physicomechanical, and Other Properties of Composites Based on Ultra-High Molecular-Weight Polyethylene, Polytetrafluoroethylene, and Еthylene–Tetrafluoroethylene Copolymer with Quasicrystalline Filler Al–Cu–Fe

Tribological, Physicomechanical, and Other Properties of Composites Based on Ultra-High Molecular-Weight Polyethylene, Polytetrafluoroethylene, and Еthylene–Tetrafluoroethylene Copolymer with Quasicrystalline Filler Al–Cu–Fe

Fluoroplastic- and Bio-Based Composites Materials for PEM Fuel Cells Bipolar Plates

Conductive polymer composite materials for polymer electrolyte membrane fuel cells bipolar plates have been successfully prepared from renewable plant biomass sources and copolymers of tetrafluoroethylene with vinylidenefluoride. The composites are based on various conductive fillers (natural, oxidized and colloidal graphite’s) and polymer binder (the 5-HMF synthesis by-product or fluoroplastic). The influences of type and content of binder and type of conductive filler on the mechanical properties and conductivity were investigated. Conductivity of the composites decreases with increasing of polymer content, but its mechanical properties changes inversely. Composite based on 5-HMF by-products (content 30 wt.%) and colloidal graphite as a filler meets the DOE requirements for a mechanical strength. Flexural and compressive strengths were 25 and 32 MPa, respectively. Composites based on fluoroplastic 32 (content 30 wt.%) and fluoroplastic 42 (content 20 wt.%) with colloidal graphite as a filler and fluoroplastic 42 (content 20 wt.%) with nature graphite have flexural strength values close to the target value of DOE and amounted to 24, 17 and 19 MPa, respectively. Interfacial contact resistance depends to a greater extent on the nature of the filler and is maximum for composites based on natural graphite. Composites based on fluoroplastic 42 at any filler content correspond to the requirements DOE ≤ 0.01 ohm∙cm2. Composite based on 5-HMF synthesis by-product (resin) and fluoroplastic with conductive filler (colloidal graphite) shows a great potential application as bipolar plates for PEMFCs.

Fluoropolymer impregnated graphite foil as a bipolar plates of vanadium flow battery

Renewable energy in recent years plays an increasingly important role in the energy industry. Therefore, the problem of inventing efficient and affordable energy storage devices is of current importance. Vanadium redox flow battery stands out between a wide range of various chemical sources of electric energy. Discovering the way for optimizing the price of energy storage is one of the most important questions of the mentioned battery. New graphite-polymer composite materials study shows that they may become a replacement for commonly used brittle graphite. The current article presents the study of graphite foil (or flexible graphite) filling with a copolymer of tetrafluoroethylene and vinylidene fluoride F-42 properties. The article uses an implementation approach of putting the fluoropolymer into the pores of graphite foil, which shows a slight decrease in electrical conductivity, while a significant increase in its electrochemical stability in comparison with untreated graphite foil. Testing results of such material as current collectors (or bipolar plates) in a single membrane-electrode assembly of vanadium redox flow battery cell show peak value of discharge power density of 843 mW/cm2, energy efficiency of 78%-79% during cycling at 200 mA/cm2 allowing us to assume the possibility of its successful application in redox flow battery stacks.

Efficient mineralization of ethylene-tetrafluoroethylene copolymer in superheated water with permanganate

Copolymer of ethylene and tetrafluoroethylene (ETFE) was treated in superheated water with KMnO4. ETFE efficiently decomposed to F– and CO2. Specifically, when ETFE (30 mg) was treated for 6 h with aqueous KMnO4 (52.7 mM; the molar amount was 1.7-fold excess of that of the fluorine atoms in ETFE) at 320 °C, the yields of F– and CO2 were 92 ± 1% and 73 ± 8%, respectively, and the total organic carbon content in the reaction solution was reduced to 4% of the carbon atom number in the initial ETFE. When the reactivity of ETFE was compared with that of poly(vinylidene fluoride) (PVDF), that is, an isomer of ETFE, ETFE required higher temperature to achieve mineralization. The present approach can reduce the reaction temperature allowing efficient mineralization of ETFE by 60 °C, compared to the previous method using supercritical water with dioxygen.

Surface functionalization of ethylene–tetrafluoroethylene copolymer film with poly(methyl methacrylate) via chemical radical polymerization

The surface of a poly(ethylene-co-tetrafluoroethylene) (ETFE) film was modified by grafting of methyl methacrylate (MMA) by using diethyl(1,10-phenanthroline N1,N10)zinc (Phen-DEZ) and oxygen molecules as the radical initiator. Fourier transform infrared (FT-IR) spectra and Raman spectra of polymethylmethacrylate-grafted-ETFE (ETFE-g-PMMA), showed absorption peaks attributed to carbonyl functionalities. And the thermal decomposition of ETFE-g-PMMA was observed in two stages. The first weight loss step was due to the disruption of the grafted PMMA polymer, while the second degradation step was likely due to thermal disruption of ETFE itself. These results provide clear evidence of PMMA grafting onto ETFE film. The grafting yield of MMA was found to be affected by the polymerization temperature, reaction time, and concentration of Phen-DEZ. Analysis of the surface morphology of the film by atomic force microscopy (AFM) suggests that MMA was grafted on the surface of the ETFE film. In addition, the water contact angle on the hydrophobic surface of the ETFE film changed from 94.6° to 65.5° depending on the graft of PMMA, resulting in hydrophilicity. Moreover, the results of the dyeing experiment showed that only the surface of the ETFE film was decorated with MMA and the interior was unchanged.