Tefzel

Copolymeis of ethylene [74-85-1] and tetiafluoioethylene [116-14-3] (ETFE) have been alaboiatory curiosity for more than 40 years. These polymers were studied in connection with a search for a melt-fabricable PTFE resin (1 5) interest in them fell with the discovery of TFE—HFP (FEP) copolymers (6). In the 1960s, however, it became evident that a melt-fabricable fluorocarbon resin was needed with higher strength and stiffness than those of PTFE resins. Earlier studies indicated that TFE—ethylene copolymers [11939-51 -6] might have the right combination of properties. Subsequent research efforts (7) led to the introduction of modified ethylene—tetrafluoroethylene polymer [25038-71-5] (Tefzel) by E. I. du Pont de Nemours Co., Inc, in 1970. 

Ethylene and tetrafluoroethylene are copolymerized in aqueous, nonaqueous, or mixed medium with free-radical initiators. The polymer is isolated and converted into extmded cubes, powders, and beads, or a dispersion. This family of products is manufactured by Du Pont, Hoechst, Daikin, Asahi Glass, and Ausimont and sold under the trade names of Tefzel, Hostaflon ET, Neoflon EP, Aflon COP, and Halon ET, respectively. 

Long-term heat-aging tests on Tefzel 280 are in progress. It is expected that its continuous-use temperature will be above 150°C. 

The thermodynamic properties of Tefzel 200 and 280 are shown in Table 2 the annual rate of loss of weight with thermal aging for Tefzel 200 ranges from 0.0006 g/g at 135°C to 0.006 g/g at 180°C after an initial loss of absorbed gases of 0.0013 g/g at elevated temperature. The excellent thermal stabihty of ETEE is demonstrated by aging at 180°C at this temperature, the annual weight loss of six parts per 1000, or a 1% weight loss, takes almost two years. 

Pressure, kPa Velocity, cm/s Wear factor, K X 10, Tefzel. 1/Pa Metal... 

Table 5. Tefzel Resistance to Chemicals after Seven Days Exposure ...

Water absorption of Tefzel is low (0.029% by weight), which contributes to its outstanding dimensional stabiUty as well as to the stabiUty of mechanical and electrical properties regardless of humidity. 

The foUowiug permeabihty values were determiued on Tefzel film (100-)J.m, ASTMD1434) at25°C (1 nmol/m-s-GPa = 0.5 cc-mil/100 in. d-atm) ... 

Tefzel grade Form Melt flow, g/10 min Appheation... 

Ultrasonic Welding. Ultrasonic welding has been appHed to Tefzel with weld strength up to 80% of the strength of the base resin. Typical conditions include a contact pressure of 172 kPa (25 psi) and 1—2 s cycle time. The two basic designs, the shear and butt joints, employ a small initial contact area to concentrate and direct the high frequency vibrational energy. 

Potting. Potting of wire insulated with Tefzel has been accompHshed with the aid of a coating of a coUoidal siHca dispersion. The pots produced with a polysulfide potting compound meeting MIL-S-8516C Class 2 standards exhibit pullout strengths of 111—155 N (25—35 Ibf). 

Bonding. Surface treatment, such as chemical etch, corona, or flame treatments, is required for adhesive bonding of Tefzel. Polyester and epoxy compounds are suitable adhesives. 

Large quantities of Tefzel have been processed and used in many demanding service appHcations. No cases of permanent injury have been attributed to these resins, and only limited instances of temporary irritation to the upper respiratory tract have been reported (35). 

Under normal processing conditions at 300—350°C, Tefzel resins are not subject to autocatalytic degradation. However, extended overheating can result in "blow-backs" through extmder feed hopper or barrel front. 

Prolonged soldering in confined spaces with restricted air circulation requires ventilation. A small duct fan is recommended for hot-wire stripping. Tefzel articles should not be exposed to welding conditions. 

The limiting oxygen index of Tefzel as measured by the candle test (ASTM D2863) is 30%. Tefzel is rated 94 V-0 by Underwriters Laboratories, Inc., in their burning test classification for polymeric materials. As a fuel, it has a comparatively low rating. Its heat of combustion is 13.7 MJ/kg (32,500 kcal/kg) compared to 14.9 MJ /kg (35,000 kcal/kg) for poly(vinyHdene fluoride) and 46.5 MJ /kg (110,000 kcal/kg) for polyethylene. 

The Du Pont HaskeU Laboratory for Toxicology and Industrial Medicine has conducted a study to determine the acute inhalation toxicity of fumes evolved from Tefzel fluoropolymers when heated at elevated temperatures. Rats were exposed to decomposition products of Tefzel for 4 h at various temperatures. The approximate lethal temperature (ALT) for Tefzel resins was deterrnined to be 335—350°C. AH rats survived exposure to pyrolysis products from Tefzel heated to 300°C for this time period. At the ALT level, death was from pulmonary edema carbon monoxide poisoning was probably a contributing factor. Hydrolyzable fluoride was present in the pyrolysis products, with concentration dependent on temperature. 

Whereas Tefzel is said to be an internally stablised copolymer of TFE and ethylene, other copolymers that are compounds of similar copolymers with stabilisers of antioxidants are now also available (Hostaflon ET by Hoechst and Aflon by Asahi Glass Co.). Glass-fibre-filled grades are also available. 

ETFE Tefzel ethylene-tetrafluoroethylene copolymer. (For chemical resistance, see FEP ratings.) Tefzel is a Du Pont registered trademark. 

ETFE CF2=CF2 CH2CH2 CF2=CFORf or CH2=CHRf Aflon COP Halon ET Hostaflon ET Neoflon EP Tefzel Asahi Glass Ausimont Hoechst Dai km Du Pont Japan Italy USA Germany Japan USA... 

The XK column system is a medium-pressure jacketed glass column system designed for operating pressures up to 5 bar (0.5 MPa). Column dead volumes are less than 0.1% of the total column volume. Wetted materials include EPDM, TEFZEL, superpolyoxymethylene, and flurorubber. Columns use nylon nets of 10-)Lim mesh size and may be used with most SEC media with particle diameters >20 /xm. Columns are intended for use with aqueous solutions and... 

Ethylene trifluoroethylene (Tefzel) (ETFE) has good mechanical properties from cryogenic levels to 350°F (177°C). It has an upper continuous working temperature limit of 300°F (149°C). 

The electrochemical cell for the EXAFS experiments (Figure 1) was machined from a teflon cylinder (6 cm diameter x 6 cm high) and was provided with contacts for all electrodes as well as teflon fittings for the injection of electrolyte. The electrode was placed flat on the top of the cell and covered with a thin Tefzel (E. 

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