Ethylene tetrafluoroethylene copolymer chemical properties

Ethylene Tetrafluoroethylene Copolymer - Thermoplastic comprised of an alternating copolymer of ethylene and tetrafluoroethylene. Has high impact resistance and good abrasion resistance, chemical resistance, weatherability, and electrical properties approaching those of fully fluori-nated polymers. Retains mechanical properties from cryogenic temperatures to 356°F. Can be molded, extruded, and powder-coated. Used in tubing, cable and wire products, valves, pump parts, wraps, and tower packing in aerospace and chemical equipment applications. Also called ETFE. 

Ethylene-Tetrafluoroethylene Copolymer n A copolymer of ethylene and tetrafluoroethylene (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. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, poly(vinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on CTFE. 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

Fluorinated ethylene propylene (FEP), copolymer of tetrafluoroethylene (TEE) and hexafluoropropylene (HFP) has physical and chemical properties similar to those of PTFE but differs from it in that FEP can be processed by standard melt-processing techniques. 

Hexafluoropropylene is produced by the pyrolysis of tetrafluoro-ethylene. The copolymer of hexafluoropropylene with tetrafluoroethylene is a medium-grade thermoplast with a crystallinity of 40-50% (drawn) to 50-70 % (annealed). The copolymer has similar mechanical and chemical properties to poly(tetrafluoroethylene), but can be molded and extruded. 

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

Fluoropolymers, such as copolymer of ethylene and tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance.36... 

Copolymers of ethylene and tetrafluoroethylene (ETFE) essentially comprise alternating ethylene and TFE units. They have an excellent balance of physical, chemical, mechanical, and electrical properties, are easily fabricated by melt-processing techniques, but have found little commercial utility, because they exhibit a poor resistance to cracking at elevated temperatures.59 Incorporation of certain termonomers, so-called modifiers, in amounts 1 to 10 mol% markedly improves the cracking resistance, while maintaining the desirable properties of the copolymer.60 61... 

Perfluorinated ethylene-propylene (FEP) is a copolymer of tetrafluoroethylene (TFE) and hexafluoro-propylene (HFP). It has the basic properties of poly-tetrafluoroethylene such as chemical resistance, low friction, and good electrical properties. FEP was the first tmly melt processible perfluoropolymer developed in the 1950s and commercialized in 1960. 

ETFE polymers are melt processible. Commercial ETFE is a copolymer of ethylene and tetrafluoroethylene. They have lower chemical resistance and thermal stability than perfiuorinated polymers. ETFE exhibits excellent resistance to radiation and can stand up to 200 megarads of exposure to cobalt 60. It is a tough thermoplastic available in different viscosities, which can be processed by techniques applicable to polyethylene. ETFE resins are specified by ASTM Method D3159, which also provides procedures or references to other ASTM methods for the measurement of resin properties. Commercial FEP resins offered by major manufacturers have been listed in Tables 6.15 through 6.18. 

Chlorotrifluoroethylene-ethylene copolymers (ECTFE) contain about 50 mole % chlorotrifluoroethylene. These copolymers are generally similar to the tetrafluoroethylene-ethylene copolymers (section 7.9) in that they are melt-processable and have high impact strength and good chemical resistance. Comparative values for some properties are given in Table 7.1. The temperature range of useful performance is from about — 80°C to 170°C. Chlorotrifluoroethylene-ethylene copolymers find use in injection mouldings for chemical process equipment and cable insulation. 

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