Ethylene-tetrafluoroethylene Copolymer Research Articles

Structure and mechanical behaviour of short glass fibre-reinforced ethylene-tetrafluoroethylene copolymers

The mechanical behaviour of a copolymer, consisting of ethylene, tetrafluoroethylene, hexafluoropropylene and perfluoropropylvinylether, unfilled and filled with short glass fibres has been investigated for strains less than 5%. Different deformation modes at room temperature and at 80 °C were recorded with a video system. The resulting stress-strain, relaxation and shrinkage curves are described with a model consisting of seven basic rheological elements of three different types: spring (Hooke model), dashpot (Newton model) and slip-element (St. Venant model). This seven-element model gives a very good approximation of all the investigated deformation modes and allows an interpretation of relaxation and retardation times of polymer segments. The plastic deformation, described by the slip-element, is assumed to be caused by slip processes in the highly disordered crystallites of the copolymer matrix.

Structure and mechanical behaviour of short glass fibre-reinforced ethylene-tetrafluoroethylene copolymers

A copolymer of ethylene, tetrafluoroethylene, hexafluoropropylene and perfluoropropylvinyl-ether has been investigated. Uniaxial tensile tests at small strains showed improved mechanical properties, when the copolymer was filled with short glass fibres. This is due to a change in superstructure, as can be seen with small-ange X-ray scattering (dynamic measurements during heating with synchrotron radiation)

Plasma treatment of tetrafluoroethylene-ethylene copolymers for adhesive bonding

The aim of this work was to improve adhesion to tefzel using plasma surface treatment. The plasmas used were O 2 , and NH 3 . Joints ,ade from the adherends using several commercially available epoxy adhesives were tested using a double lap shear configuration. Measured bond strenghts for the treated adherends were as much as 30 times greater than those for the untreated materials. Examination of the O 2 plasma-treated Tefzel by electron spectroscopy for chemical analysis indicated a surface oxidation increase of about 7NDASH;8% over the untreated material, with the oxide being primarily in the form of an ester.

Irradiation effects of excimer laser radiation and electron beam on polypropylene and ethylene-tetrafluoroethylene copolymer films

The irradiation effects of the intense ultraviolet radiation from an excimer laser on polypropylene (PP) and ethylene-tetrafluoroethylene (ETFE) copolymer films are compared with those from electron beam studies. Irradiation of PP films with a KrF laser and an electron beam induced the degradation of the polymer, and use of an ArF laser selectively decomposed the alkyl phenol type additive contained as an antioxidant in PP instead of degrading the polymer. Irradiation with a KrF laser induced the carbonization of ETFE copolymer due to polymer degradation, and irradiation with an ArF laser and an electron beam formed CO and CC groups in the polymer chains.

Long lived fluoropolymeric radicals in irradiated fluoropolymer powders at room temperature

Fluoropolymeric radicals formed in irradiated polyperfluoroethylene-propylene (FEP), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE) powders have the life time over 5 years at room temperature. Those formed in irradiated tetrafluoroethylene-ethylene copolymers (F 40, polyvinylidene fluoride (PVDF) powders lived at room temperature about 1 year. They have the chemical reactivity to initiate graft reaction. The principles of radical stability are considered and discussed. Study on decay of fluorine containing radicals at room temperature formed in fluoropolymer films irradiated with fast electrons have been reported (1–6). This paper reported results of decay of fluorine containing radicals at room temperature formed in irradiated fluoropolymer powders. Films and powders are different state of matter. By comparison the decay of radicals in films and powders, we have found the effects of state. Meanwhile, the graft reaction of irradiated fluoropolymer powders needs the data about decay of radicals at room temperature. Before irradiation, samples dried at 100–120°C under high vacuum for 8 hrs, then placed in desiccator. After irradiation, samples still placed in desiccator for ESR measurement. G R is the G value of fluororadicals.

Wide-angle X-ray studies on ethylene-tetrafluoroethylene (ETFE) copolymers

The orientation parameters 〈P 2〉 of the chain segments in the amorphous layers of uniaxially drawn ethylene-tetrafluorethylene (ETFE) copolymers with different side chain modifications were determined from the separated amorphous halo of wide angle X-ray scattering (WAXS) measurements. The orientation distribution of the crystallographic axes in the ‘crystal’ domains, which show essentially a two-dimensional order in lateral direction, was obtained from the analysis of hk0 reflections. The crystal orientation is independent of the side chain modifications. Both the mean lattice constant and the mean extension of the coherent scattering domains were determined to be temperature-dependent using synchrotron radiation. The anomaly of these parameters at about 100°C is attributed to a transition of the crystal structure.

ESCA study of poly(vinylidene fluoride), tetrafluoroethylene-ethylene copolymer and polyethylene exposed to atomic oxygen

The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinylidene fluoride) (PVDF), tetrafluoroethylene-ethylene copolymer (TFE/ET) and polyethylene (PE) exposed to atomic oxygen (O( 3P)), in or out of the glow of a radio-frequency O 2 plasma, were compared. ESCA spectra of PE films exposed to O( 3P) in low Earth orbit (LEO) on the STS-8 Space Shuttle were also examined. Apart from O( 3P)-induced surface recession (etching), the various polymer films exhibited surface oxidation, which proceeded towards equilibrium saturation oxygen levels. The maximum surface oxygen uptakes for in-glow or out-of-glow exposures were in the order: PE > TFE ET > PVDF ; for PE itself, the oxygen uptakes were in the order: in glow > out of glow > LEO. Given prior ESCA data on poly(vinyl fluoride) and polytetrafluoroethylene films exposed to O( 3P), the extent of surface oxidation is seen to decrease regularly with increase in fluorine substitution in a family of ethylene-type polymers.

Effect of radiation cross-linking on the thermomechanical properties of fibres from a tetrafluoroethyleneethylene copolymer

The effect of radiation dose on the heat-resistance of fibres from a tetrafluoroethyleneethylene copolymer has been investigated.

Reactions of atomic oxygen (O( 3P)) with various polymer films

Thin films of various polymers were exposed at ambient temperature to ground-state oxygen atoms (O( 3P)) downstream from a radio-frequency O 2 plasma or glow discharge. The polymer films examined were a polyimide (Kapton), poly(ethylene terephthalate), polystyrene, high- and low-density polyethylenes, poly(vinyl fluoride), poly(vinylidene fluoride), alternating tetrafluoroethylene-ethylene copolymer, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer. The relative etch rates for the various polymer films exposed ‘out of the glow’ to O atoms with 0·04 eV translational energy are compared with corresponding literature values obtained from low-pressure, oxygen discharge studies involving exposure ‘in the glow’ and from the Space Shuttle STS-8 flight (with O atoms in low Earth orbit having collisional energy of ≈ 5 eV). The etch rate for Kapton exposed ‘out of the glow’ to 0·04-eV O atoms is also compared with etch rates obtained from various neutral and ion beam experiments (with O O + having impact energies ranging from 0·14 to 800 eV). The etch rate data for Kapton fit reasonably well a logarithmic plot, with positive slope, of reaction probability versus O( 3P) impact energy. ESCA spectra of Kapton before and after reaction with O( 3P) indicated steady-state competition between surface recession (etching) and oxidation.

Complex-forming polymer prepared by electron beam radiation-induced graft polymerization

In order to prepare a complex-forming polymer useful as a selective adsorbent, radiation-induced graft polymerization of acrylonitrile onto a fibrous tetrafluoroethylene ethylene copolymer has been studied by using preirradiation method. The resulting grafted fibers were treated with 3% hydroxylamine alcohol-water solution, followed by controlling in alkali solution. The adsorbents containing amidoxime are able to take up transition metal ions from neutral and weakly acidic solutions while not sorbing the ions of alkaline and alkaline earth metals to any significant extent. It was shown that by introducing a small amount of hydrophilic groups to the fiber, it was possible to increase the exchange rate between the external water and the internal water interacted with functional groups in polymer matrix and to induce the diffusion of hydrated metal ions. The efficiency for adsorption of transition metal ions was successfully improved either by adding small amount of hydrophilic part composed of poly(acrylic acid) or by restricting the distribution of amidoxime groups at the fiber surface. A high stability of this adsorbents to various treatments ( alkali treatment at 80° C, contact with seawater for 24 h at 30° C, etc.) was confirmed. It's applicability to the recovery of uranium from seawater is demonstrated by laboratory scale experiments.

Study of the structure of the tetrafluoroethylene-ethylene copolymer by the method of pyrolytic gas chromatography

The principal features of the rupture of CC bonds differing in activation energy, in macromolecules of the tetrafluoroethylene-ethylene copolymer, at a pyrolysis temperature of 923 K in a stream of helium, were determined using the method of pyrolytic gas chromatography. The possibility of the determination of the distribution of monomer units in the macromolecule of the copolymer from the composition of the volatile pyrolysis products has been demonstrated for the first time. New structural characteristics are proposed, and numerical values characterizing the distribution of monomer units in dependence on the composition of the copolymer are given.

Scanning electron microscopy of nuclear pore filters in poly(ethylene terephthalate) and ethylene-tetrafluoroethylene copolymer

The interior of nuclear pore filters was observed by high resolution scanning electron microscopy. In poly(ethylene terephthalate) the interior of the hole with nodules of some widths was observed and the tapering angle observed from the cross section of the hole agreed with that calculated from the ratio of etching rates. In ethylene-tetrafluoroethylene copolymer the holes lie among the fibrils. Only ∼40% fission fragments penetrated and the residual remained in the 12 μm thick film from the observation of cross section of holes and from measurement of radioactive distribution of incident nuclides in the film. In either film the irregular surface was assumed to be induced by the difference of etching between the amorphous and the crystalline regions.

ESCA applied to polymers. XXI. Investigation of sample‐charging phenomena

AbstractSample‐charging phenomena arising in the ESCA experiment have been investigated for a series of polymers. For samples studied as films or powders mounted insulated from the spectrometer probe and for gold under similar conditions it is shown that over a wide range of operating conditions, equilibrium charging shifts are characteristic of the sample and show a strong dependence on the theoretically calculated total photoionization cross sections. The surface sensitivity of the phenomenon has been demonstrated by monitoring changes in charging shifts as a function of hydrocarbon contamination. For polymer films mounted directly in contact with the spectrometer, the charging shifts exhibit time‐dependent behavior. The utility of studying sample‐charging shifts as an interesting phenomenon in its own right is demonstrated by reference to changes which occur consequent upon surface modification of an ethylene–tetrafluoroethylene copolymer system in RF plasmas excited in inert gases.

ESCA applied to polymers. XVIII. RF glow discharge modification of polymers in helium, neon, argon, and krypton

AbstractThe crosslinking of an ethylene–tetrafluoroethylene copolymer by exposure to a variety of inert gas plasmas, excited by an inductively coupled radiofrequency (RF) field, has been studied. The rates for direct and radiative energy‐transfer processes are determined within the framework of a kinetic model of the system and are shown to have a strong dependence on the sustaining gas, as do the average depths of penetration of the ions and metastable species. Helium is found to be the most efficient gas for the crosslinking of the outermost few monolayers whereas the crosslinking of the subsurface and bulk polymer is best effected by neon. Madelung charge potential calculations have been performed to simulate the experimentally determined x‐ray photoelectron spectroscopy (ESCA) spectra to elucidate several features of the mechanisms involved.

Adhesion of ethylene-tetrafluoroethylene copolymer with silicate glasses

The adhesive strength of ethylene-tetrafluoroethylene copolymer (ETFE) was measured on silicate glass substrates. A value of over 300 kg/cm 2 obtained with a commercial soda-lime-silica glass and this initial adhesiveness was attributed to the marked wettability of molten ETFE and its chemical structure. Since the decrease in the adhesive strength was small after immersion in water for a dealkalized soda-lime-silica glass, Pyrex, and a soda-lime-silica glass coated witn In 2O 3, it was inferred that the sodium ions in the soda-lime-silica glass played a fundamental role in lowering the adhesive strength in the presence of water. Pretreatment with N-( β-aminoethyl)- γ-aminopropyl-trimethoxy silane markedly improved the water durability of the adhesive strength.

Properties of a new thermoplastic fluorinated polymer

The properties of a new thermoplastic polymer, tetrafluoroethylene-ethylene copolymer (TE) are reported. It is a crystalline thermoplastic melting around 275 and contains essentially alternating monomer units with minor amounts of additional perfluorinated units. The copolymer has excellent mechanical properties both at low and high temperature; it exhibits moderate stiffness, good toughness and good creep behaviour. Dielectric constant and loss factor are low; chemical, thermal and weather resistance are good. TE is particularly suited for extrusion applications, especially for electrical insulation purposes and for chemical applications.

The structural changes produced by γ-radiation in hydrogen containing polyfluoroethylenes

Wide and small angle X-ray diffraction methods were used to study the structural changes in polyethylene, polyvinyl fluoride, polytrifluoroethylene, and also in the vinylidene fluoride-tetrafluoroethylene and tetrafluoroethylene-ethylene copolymers after exposure to 100–1500 Mrad doses of γ- 60Co radiation. The radiation resistance of crystalline and macromolecular structures was found to decrease as the number of fluorine atoms increased in the polymers. All the polymers used (except polyvinyl fluoride) showed a phase transition due to chain defects when they were irradiated; this led to a larger symmetry of the unit cell. The differing behaviour of block and powder samples of H containing polyfluoroethylenes during irradiation was found to diminish with increasing content of fluorine atoms. In addition to the existence of different mechanisms of structural change in the latter polymers there were some characteristics of the polyvinyl fluoride which are explained here.