Copolymer Of Tetrafluoroethylene Research Articles

The Application of Radio Frequency Magnetron Sputtering for Fluoropolymer Surface Modification

The paper investigated the properties of the multilayer system: metal with polymer layer modified by radio frequency magnetron sputtering of a solid target made from hydroxyapatite. The material of the polymer layer is thermoplastic copolymer of tetrafluoroethylene with vinylidene fluoride. The roughness parameters of metal, polymer, and hybrid substrates are determined using atomic-force microscope. Calcium phosphate coatings increase the surfaces roughness of polymer and metal materials, thus presenting a stimulating factor for the attachment and proliferation of osteogenic cells. Wettability of the coatings was investigated by the “sit” drop method of the “Krüss Easy Drop” installation by measuring the effective contact angle. The hydrophobic polymer surface becomes hydrophilic after modification and the surface free energy increases.

Polarization of block textured films of ferroelectric copolymers of vinylidene fluoride with tetrafluoroethylene in an external field

The polarization of oriented films of the ferroelectric copolymer of vinylidene fluoride and tetrafluoroethylene in a sinusoidal electric field is studied. In low fields, the copolymer behaves as a linear dielectric whose permittivity nonlinearly increases with the amplitude of the alternating field. This behavior is related to the preferential orientation of the dipole moment of the chain along the normal to the surface and to the monocrystal-structure formation. In higher fields, the hysteresis behaves formally coincidently with the behavior of an antiferroelectric. The important role of through stressed chains in the amorphous phase in the initiation of domains of a new direction in polar crystals is observed. Increased adsorption of water molecules on the surface of a polarized film is found and is attributed to the formation of the final density of the stable polarization charge on it.

Fluoropolymers: Origin, Production, and Industrial and Commercial Applications

Fluoropolymers have had a profound effect on all aspects of industry since their discovery during the 1930s. This review briefly describes the historical development of the fluoropolymer industry, with a focus on traditional fluoroplastics, and lists the major industrial and commercial materials currently in use. These include polytetrafluoroethylene (PTFE, Teflon), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), the ethylene copolymer of tetrafluoroethylene (ETFE), the ethylene copolymer of chlorotrifluoroethylene (ECTFE), perfluoroalkoxy (PFA), polyvinylfluoride (PVF), polyvinyldifluoride (PVDF), Nafion, fluoroethylenevinylether (FEVE), a semicrystalline three component terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), Teflon-AF, Cytop, and Hyflon. The production, processing, and properties of these fluoropolymers are discussed, together with examples of the specific uses in chemical industry, manufacturing, electronics, architecture, energy, health and domestic sectors. Other related fluoropolymers such as fluoroelastomers, perfluoropolyethers, and fluorosurfactants are briefly mentioned. Environmental aspects of fluoropolymers are considered as is the current state of the fluoropolymer industry.

Electrical, mechanical, and crystallization properties of ethylene‐tetrafluoroethylene copolymer/multiwalled carbon nanotube composites

ABSTRACTMultiwalled carbon nanotubes (MWCNTs) were melt‐mixed in a conical twin‐screw extruder with a random copolymer of ethylene and tetrafluoroethylene. Surprisingly, the electrical percolation threshold of the resultant composites was quite low; ∼0.9 wt %. In fact, this value is as low or lower than the value for most MWCNT/semicrystalline polymer composites made with roughly equivalent aspect ratio tubes mixed in a similar manner, for example, melt mixing. This low percolation threshold, suggestive of good dispersion, occurred even though the polymer surface energy is quite low which should make tubes more difficult to disperse. Dynamic mechanical measurements confirmed the rather low percolation threshold. The effect of nanotubes on crystallization kinetics was quite small; suggesting perhaps that a lack of nucleation which in turn reduces/eliminates an insulating crystalline polymer layer around the nanotubes might explain the low percolation threshold. Finally, the modulus increased with the addition of nanotubes and the strain at break decreased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41052.

Efficient-Oxygen Induced Mineralization of Melt-Processable Fluoropolymers in Subcritical and Supercritical Water

The decomposition of poly(vinylidene fluoride) (PVDF) and ethylene–tetrafluoroethylene copolymer (ETFE) in subcritical and supercritical water was investigated. Heating PVDF in supercritical water at 380 °C for 6 h with an approximately 5.8-fold molar excess of O2 relative to the fluorine or carbon content in the polymer afforded F– and CO2 in 96.9% and 99.3% yields, respectively. ETFE was also efficiently mineralized to F– (97.6%) and CO2 (98.2%) with an 11-fold molar excess of O2 relative to the fluorine or carbon content of the polymer under the same reaction conditions. The PVDF and ETFE reactivities differed markedly under argon: PVDF formed mainly F–, CO2 formation was suppressed, and a carbon-rich residue formed; in contrast, ETFE was unreactive. This difference suggests that PVDF decomposed via dehydrofluorination in the absence of O2, whereas ETFE did not. Adding stoichiometric Ca(OH)2 to the reaction in the presence of O2 afforded X-ray spectrometrically pure CaF2.

Ferroelectric polymer scaffolds based on a copolymer of tetrafluoroethylene with vinylidene fluoride: Fabrication and properties

A solution blow spinning technique is a method developed recently for making nonwoven webs of micro- and nanofibres. The principal advantage of this method compared to a more traditional electrospinning process is its significantly higher production rate. In this work, the solution blow spinning method was further developed to produce nonwoven polymeric scaffolds based on a copolymer of tetrafluoroethylene with vinylidene fluoride solution in acetone. A crucial feature of the proposed method is that high-voltage equipment is not required, which further improves the method's economics. Scanning electron microscopy analysis of the samples demonstrated that the surface morphology of the nonwoven materials is dependent on the polymer concentration in the spinning solution. It was concluded that an optimum morphology of the nonwoven scaffolds for medical applications is achieved by using a 5% solution of the copolymer. It was established that the scaffolds produced from the 5% solution have a fractal structure and anisotropic mechanical properties. X-ray diffraction, infrared spectroscopy, Raman spectroscopy and differential scanning calorimetry demonstrated that the fabricated nonwoven materials have crystal structures that exhibit ferroelectric properties. Gas chromatography has shown that the amount of acetone in the nonwoven material does not exceed the maximum allowable concentration of 0.5%. In vitro analysis, using the culture of motile cells, confirmed that the nonwoven material is non-toxic and does not alter the morpho-functional status of stem cells for short-term cultivation, and therefore can potentially be used in medical applications.

Structural Aspects at Phase Transitions in Ferroelectric Copolymers of Vinylidenefluoride and Tetrafluoroethylene

Permittivity and conductivity low-voltage temperature dependences of a ferroelectric copolymer of vinylidenefluoride VDF with tetrafluoroethylene TFE in the ferroelectric to paraelectric phase transition range were investigated. The as received films obtained by crystallization from a solution had the metastable structure shown in particular in coexistence of ferroelectric and paraelectric phases below a Curie point. Temperature dependences of electrical characteristics in the first and second cycles of heating differ. Low glass transition (–40 ºC) facilitate intensive micro-Brownian chains mobility in the amorphous phase at ambient temperatures and above. As per the x-ray and spectroscopic data, the first heating cycle will result in a recrystallization process for molecular structure improvement. Asymmetry of temperature dependence of a dielectric susceptibility in a vicinity of “order-disorder” phase change is found out. For the first time paid attention to the fact that for crystalline polymer ferroelectrics interpretation of the parameters of the temperature dependences of the dielectric susceptibility in the cycle of heating near the phase transition point should take into account the possibility of the premelt processes. First the method of IR spectroscopy shows that the melting of ordered structures, emerging secondary crystallization is accompanied by a change of the basic parameters (frequency position, the integral intensity and half-width) component of the doublet of valence vibrations of C-H groups. Such structural changes lead to the emergence of “anomalies” on the temperature dependences of conductivity.

Transparent Multilayer ETFE Panels for Building Envelope: Thermal Transmittance Evaluation and Assessment of Optical and Solar Performance Decay due to Soiling

This paper is divided in two sections. The first section present the measurement and evaluation of soiling effects of spectral light and solar transmittance decay of Ethylene Tetrafluoroethylene Copolymer (ETFE) membranes after three and six months of exposure in Milano city outdoor urban conditions, with different tilt and orientation. The obtained values where use to compute thermal and solar properties of a multilayer ETFE panel.The second section presents the results of an experimental campaign for measuring thermal transmittance of a non-pneumatic and non-cushion shape double layer ETFE sample panel realized with two membranes parallel to each other and tensioned on a frame. The thermal transmittance measurement reflects ISO 9869 measurement approach combined with the use of a thermographic camera to evaluate surface temperatures over the sample panel.

Uniaxial deformation and orientation of ethylene–tetrafluoroethylene films

This study concerns the thermal and mechanical response of several commercial grades of ethylene – tetrafluoroethylene copolymer films. Differential scanning calorimetry was used to show that, although films have similar degrees of crystallinity and melting temperature, the melting endotherms and crystallisation exotherms differ between materials, suggesting small changes in composition between manufacturers. Films were deformed in tension at a range of temperatures and rates. Selected films were unloaded immediately after stretching, and measurement of the elastic recovery highlighted further differences between materials. Batches of films were pre-drawn uniaxially above the glass transition and immediately quenched. When these materials were subsequently re-drawn below the glass transition temperature, most of them exhibited much improved yield stress, modulus and tensile strength (improving by factors of 5, 5 and 4, respectively at a draw ratio of 3), but a reduced strain to failure. In most of the films, the pre-drawing, as well as the initial orientation of the films, is accounted for by a simple shift in the true strain axis. This is indicative of a material response dominated by entropic network stretch. It also suggests that, in the cases where strain superposition does not work, a different arrangement of crystalline lamellae may be present, limiting the extent to which improved properties can be achieved in some materials.

Heterogeneous chemical crosslinking and high-voltage polarization in a ferroelectric copolymer of vinylidene fluoride and tetrafluoroethylene

The low-temperature chemical crosslinking of a copolymer of vinylidene fluoride and tetrafluoroethylene was studied through various physicochemical methods. The reaction was conducted in solution in the presence of diethylenetriamine as a crosslinking agent. The penetration of the mixture molecules and the crosslinking agent only in the amorphous phase of the copolymer was provided via selection of the ratio between a good solvent (dimethylformamide) and a poor solvent (ethanol). Owing to this, the crosslinking reaction occurred in the amorphous phase and hardly involved the crystals. This outcome was confirmed by wide-angle X-ray diffraction data. The structural and chemical changes in the amorphous phase during crosslinking were recorded with the use of IR spectroscopy and differential scanning calorimetry. It is shown that crosslinking is accompanied by the formation of C=C bonds in the copolymer chains. The study of high-voltage polarization and conductivity during exposure to bipolar rectangular pulses suggested that crosslinking leads to an increase in the carrier concentration. It was found that the surface potentials in the films increase with an increase in the number of high-voltage pulses applied to the sample. This circumstance is attributed to the fact that the double bonds formed in the copolymer chains can effectively trap negatively charged carriers.

Thermo-stimulated luminescence analysis of powder of the gamma-irradiated tetrafluoroethylene/ethylene copolymer

The thermo-stimulated luminescence of Γ-irradiated commercial copolymers of tetrafluoroethylene with ethylene were explored. There are five intense maxima in the luminescence curves. Position, halfwidth and number of maxima remain constant at doses of irradiation from 10 kGy up to 30 kGy. The first peak at 112 K to 119 K has the greatest intensity and is found on the luminescence curves of all of the investigated copolymers except for Tefzel®. For Tefzel®, the maximum occurs at 141 K. The differences of the glow curves in the different copolymers may be the result of impurities capable of reacting with ions or radicals formed under irradiation and by differences in the copolymer’s topological structures.

Molecular-topology of powder of the γ-irradiated tetrafluoroethylene/ethylene copolymer

The molecular-topological structure of γ-irradiated commercial copolymers of tetrafluoroethylene with ethylene (CTE) were explored in the coaxial mode, which has the vectors of CTE loading and compression pressure in the same plane, and in the perpendicular mode with the two vectors perpendicular to each other. Instead of the amorphous-crystal structure observed with the coaxial orientation of the vectors, the CTEs are completely amorphous in their perpendicular orientation. Radiolysis with a dose of 140 kGy leads to the formation of a crosslinked structure for the CTEs. On irradiation, the crystals are transformed to an amorphous state and CTE can form a fully amorphous structure after 600 kGy of irradiation.

Influence of the third monomer component on the X-ray-analyzed crystal structure of ethylene–tetrafluoroethylene copolymer

Influence of the third monomer component on the crystal structure of the low-temperature phase of ethylene (E)–tetrafluoroethylene (TFE) alternating copolymer (CH2CH2CF2CF2)n was investigated by the measurement of 2-dimensional wide-angle X-ray diffraction (WAXD) diagrams. Nonafluoro-1-hexene (NFH) and hexafluoropropylene were chosen as the third monomer component (termonomer) with the side chains of C4F9 (ET-C4F9) and CF3 (ET-CF3), respectively. Although the termonomer content was low, 1.5 and 2.7mol%, respectively, the third monomer component has been found to affect more or less the crystal structure of the original 2-component ET copolymer. The crystal structure of these three types of ET copolymer is commonly of the triclinic type. In the case of ET-C4F9 terpolymer, the unit cell size and the setting angle of the planar-zigzag chains in the unit cell are almost the same as those of the 2-component ET copolymer. On the other hand, in the case of ET-CF3 terpolymer, the unit cell becomes larger and the chain setting angle is appreciably different from the 2-component ET copolymer’s case. As reported in the previous paper (Macromolecules, 44, 1540 (2011)), the long C4F9 side chains are not included in the crystal lattice but they are excluded on the lamellar surfaces, not giving significant effect on the inner structure of the unit cell. The short CF3 groups are included in the crystal lattice and expand the unit cell, resulting in the significant modification of the chain setting angle. These copolymers are known to show the phase transition between the low-temperature-phase and high-temperature phase in a certain temperature region. The transition region is not very different between the 2-component copolymer and ET-C4F9 terpolymer, while ET-CF3 terpolymer shows the transition in an appreciably low temperature region below the room temperature. The difference in such a characteristic phase transition behavior originates from the above-mentioned different situation of the long and short side groups.

Modification of tetrafluoroethylene-perfluoropropylvinyl ether copolymer films in direct-current discharge

Changes induced in the surface properties of films of a tetrafluoroethylene copolymer with perfluoropropylvinyl ether by direct-current discharge have been investigated, depending on the discharge parameters. It has been shown that the treatment of the films at the anode is more effective than at the cathode. A change in the contact properties of the modified films during their storage in air under ambient conditions and upon heating to 150°C has been examined. The chemical composition of the surface of the films after modification, storage, and heating has been studied by X-ray photoelectron spectroscopy and Fouriertransform IR spectroscopy. It has been found that dc discharge treatment significantly improves the adhesion properties of the films and barely affects their light transmission.

Research of the surface properties of the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene modified with radio-frequency magnetron sputtering for medical application

The properties of thin calcium-phosphate coatings formed by radio-frequency magnetron sputtering of a solid target made from hydroxyapatite on the surface of the thermoplastic copolymer of vinilidene fluoride and tetrafluoroethylene (VDF–TeFE) were investigated. Atomic force microscopy energy dispersive analysis and optical goniometry showed that deposited calcium-phosphate coatings change significantly the morphological, electrical, chemical, and contact properties of the surface of the initial polymeric substrates. These modified surfaces widen the scope of medical application of the thermoplastic copolymer.

Effects of Tube Materials on Capillary Chromatography Based on Tube Radial Distribution of Ternary Mixture Carrier Solvents under Laminar Flow Conditions

A capillary chromatography system was developed using an open capillary tube and a ternary solvents carrier solution of water-hydrophilic/hydrophobic organic solvent mixture. The chromatography is called a tube radial distribution chromatography (TRDC) system. The TRDC system works without applying high voltages or using specific columns, such as monolithic and packed columns. In this study, the effects of tube materials on separation performance were examined in the TRDC system, by using poly(tetrafluoroethylene) (PTFE; 100–400 μm inner diameter), polyethylene (PE; 200 μm inner diameter), and copolymer of (tetrafluoroethylene–perfluoroalcoxyethylene) (PTFE–PFAE; 100 μm inner diameter) capillary tubes. An analyte solution of 2,6-naphthalenedisulfonic acid and 1-naphthol as a model was subjected to the system with a water–acetonitrile–ethyl acetate carrier solution; 15:3:2 volume ratio (water-rich carrier) and 3:8:4 volume ratio (organic solvent-rich carrier). The flow rates were adjusted to be 0.5 μL min−1 for PTFE and PTFE–PFAE tubes as well as 2.0 μL min−1 for PE tube under laminar flow conditions. These analytes in the solution were separated in this order with the water-rich carrier solution with baseline separation in the three capillary tubes, while they were eluted in the reverse order or not separated with the organic solvent-rich carrier solution. The effects of tube temperature on separation were also examined with the water-rich carrier solution; the best resolutions were observed at 0 °C of the tube temperature. The obtained results were compared with those of fused-silica capillary tube and discussed.

Tuning the Energy Level Offset between Donor and Acceptor with Ferroelectric Dipole Layers for Increased Efficiency in Bilayer Organic Photovoltaic Cells

Ultrathin ferroelectric polyvinylidene fluoride (70%)-tetrafluoroethylene (30%) copolymer film is inserted between the poly3(hexylthiophene) (P3HT) donor and [6,6]-phenyl-C61-butyric acid methylester (PCBM) acceptor layers as the dipole layer to tune the relative energy levels, which can potentially maximize the open circuit voltage of bilayer organic solar cells. In this work, the power conversion efficiency of P3HT/PCBM bilayer solar cells is demonstrated to be doubled with the inserted dipoles.

Enhanced flow injection analysis for measurements of S-nitrosothiols species in biological samples using highly selective amperometric nitric oxide sensor

Abstract A highly selective nitric oxide (NO) sensor is fabricated and applied to devise an enhanced flow injection analysis (FIA) system for S-nitrosothiols (RSNOs) measurement in biological samples. The NO sensor is prepared using a polytetrafluoroethylene (PTFE) gas-permeable membrane loaded with Teflon AF ® solution, a copolymer of tetrafluoroethylene and 2,2-bis(trifluoroethylene)-4,5-difluoro-1,3-dioxole, to improve selectivity. This method is much simpler and possesses good performance over a wide range of RSNOs concentrations. Standard deviation for three parallel measurements of blood plasma is 4.0%. The use of the gas sensing configuration as the detector enhances selectivity of the FIA measurement vs. using less selective electrochemical detectors that do not use PTFE/Teflon type outer membranes.

UV-resistant amorphous fluorinated coating for anodized titanium surfaces

In this work, a high molecular weight copolymer of tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole (HYFLON® AD60) and two perfluoropolyethers (PFPEs) containing ammonium phosphate or triethoxysilane functionalities, FLUOROLINK® F10 and FLUOROLINK® S10 respectively, have been evaluated as protective coatings that can be easily applied on anodized titanium surfaces. Water and n-dodecane contact angle measurements have been recorded by using the sessile drop method for bare and coated surfaces in order to determine the hydrophobic and oleophobic properties of the coatings. The UV-stability of coatings have been studied by Fourier transform infrared spectroscopy (FT-IR) analyses and by observing the variation of water contact angles on coated substrates before and after UV irradiation at regular time intervals. The thickness of the fluorinated films has been measured by ellipsometry and by weight evaluation. Preliminary tests of the adhesion between films and substrate have been conducted.

Solution-processed electrophosphorescent devices with a thin fluoropolymer at the hole transport interfacial layer

Electrophosphorescent devices with ionomer-type hole transport layers were investigated. On top of the 3,4-ethylenedioxy thiophene:poly(4-styrene sulfonate) [PEDOT:PSS] structures, fluoropolymer interfacial layers (FPIs) with different side chain lengths were introduced. Both for the PEDOT:PSS/FPI (layered) and PEDOT:PSS (mixed) structures with soluble phosphorescent emitters, the short-side-chain FPIs showed higher efficiency. The difference in the electrical properties of the two FPIs for bipolar (light-emitting) devices was not clear, but the hole-only device clearly showed the favored hole injection at the PEDOT:PSS/FPI structure with a shorter side chain, a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether.