Tefzel properties

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. 

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. 

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. 

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). 

Fluoropolymers. Melt processable fluoropolymers such as Teflon FEP, Tefzel ETFE, poly(vinylidene fluoride) (Kynar), and ethylene-chlorotrifluoroethylene copolymer (Halar) are suitable for wire insulation in special applications because they combine good physical properties with low flammability. They are used for instrumentation cable in process-control rooms, as well as for computer and aircraft wiring and in military applications. The... 

Tefzel Fluoropolymer Resin, Properties Handbook, DuPont Co., No. E-31301-5 (Aug. 1996)... 

Copolymers of tetrafluoroethylene were developed in attempts to provide materials with the general properties of PTFE and the melt process-ability of the more conventional thermoplastics. Two such copolymers are tetrafluoroethylene-hexafluoropropylene (TFE-HFP) copolymers (Teflon FEP resins by Du Pont FEP stands for fluorinated ethylene propylene) with a melting point of 290°C and tetrafluoroethylene-ethylene (ETFE) copolymers (Tefzel by Du Pont) with a melting point of 270°C. These products are melt processable. A number of other fluorine containing melt processable polymers have been introduced. 

Tefzel is a rugged thermoplastic with an outstanding balance of properties. It can be reinforced with carbon or glass fibers, being the first fluoroplastic that can be reinforced, not merely filled. Because the resin will bond to the fibers, strength, stiffness, creep resistance, heat distortion temperature, and dimer sional stability are enhanced. 

This elastomer is sold under the trade name Tefzel by DuPont. ETFE is a modified partially fluorinated copolymer of ethylene and polytetrafluor-oethylene (PTFE). Since it contains more than 75% TEE by weight, it has better resistance to abrasion and cut-through than TEE while retaining most of the corrosion resistance properties. 

Table 3-01. Film Properties of DuPont Tefzel P ETFE Film...

The rotor seal is usually made from vespel which has the best mechanical properties and can be used in the range of pH 0-10. If the mobile phase has a higher pH a tefzel seal is needed which is pH-resistant up to pH 14. However, this material is less suited to withstand high pressures and its channels become narrower under such conditions. Tefzel surfaces are less smooth than the ones obtained by the manfacturing of vespel. Therefore it is recommended to use tefzel rotor seals only when necessary. 

An ionic liquid, [C4mim][NTf2], and de-ionised water were used as test fluids, with their properties summarised in Table 4.1. The experimental setup (Fig. 3.2) and details about the system were discussed in Sect. 3.4. Both inlets (T- and Y-junction) were used and the test sections were made of two types of Teflon, FEP and Tefzel, with internal diameter (ID) of 220 and 270 pm respectively, and of borosilicate glass with an internal diameter of 200 pm. Flow patterns and pressure drop measurements were carried out for different flow rates that varied from 0.07 to 11. 5 cm h for the ionic liquid and of from 0.017 to 215 cm h for water. The ionic liquid volume fraction (eil) varied from 0.05 to 0.8. In all cases, the flow rate of... 

A copolymer of ethylene and tetrafluor-oethylene (DuPont Tefzel ), ETFE is readily processed by extrusion and injection molding. It has excellent resistance to heat, abrasion, chemicals, and impact, with good electrical properties. 

Modified ETFE is less dense, tougher, and stiffer and exhibits a higher tensile strength and creep resistance than PTFE, PFA, or FEP resins. It is ductile, and displays in various compositions the characteristic of a nonlinear stress-strain relationship. Typical physical properties of Tefzel products are shown in Table 1 (33,34). Properties such as elongation and flex life depend on crystallinity, which is affected by the rate of crystallization values depend on fabrication conditions and melt cooling rates. 

Glass reinforcement improves the frictional and wear properties of modified ETFE resins (HT-2004). For example, the dynamic coefficient of friction [689.5 kPa (100 psi) at >3 m/min] for Tefzel 200 is 0.4, which drops to 0.3 for the 25% glass-reinforced product at these conditions (33). The wear factor also improves from... 

Elongations between 100 and 300% are achieved with varying methods of sample fabrication. Long-term heat-aging tests on Tefzel 280 are in progress. Early data indicate that initial properties are retained after more than 2000 h at 200° C. It is expected that the continuous use temperatm of Tefeel 280 will be above 150°C. 

ETFE polymers ("TEFZEL") modified with termonomers require great care in synthesis to Insure optimum properties. Incorporation of ethylene near 50 mole % and control of degree of alternation near 90% must be maintained in order to prevent too high a concentration of hydrocarbon branches which result from radical rearrangement of ethylene diads and triads. This same type of rearrangement is the reason why such an unusual comonomer as hexafluoroacetone is effective in improving stress crack resistance. While the hydrocarbon branches also have a beneficial effect, they must be surpressed because they are sites for oxidative attack at processing conditions. 

The remarkable properties of "TEFZEL" ETFE are best illustrated by comparison with the isomeric polydifluoroethylene. This difference can be thought of as the result of a difference in repeat unit structure. In fact, there is a remarkable similarity between ETFE and poly-1, 1, 4, 4-tetrafluorobutadlene in both chemical and physical properties, including nearly identical crystalline melting points. 

With commercialization of PFA and "TEFZEL" in 1972 a burst of enthusiasm for polymers combining the various structural characteristics ensued. Polymers developed included terpolymers of TFE/HFP/PPVE ("TEFLON" EPE [11], "Hostaflon" TFA and "TEFLON" FEE [12]). The former polymers have certain modest property advantages over blends of FEP with PFA, However, these advantages have not been sufficient to generate enthusiastic use in industry. The FEE copolymers are more interesting since, despite their hydrocarbon content, they have a balance of properties quite similar to those of PFA (Table IV), They are superior to PFA in two ways ... 

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