Tetrafluoroethylene and hexafluoropropylene

Certain CFCs are used as raw materials to manufacture key fluorinated olefins to support polymer apphcations. Thermolysis of HCFC-22 affords tetrafluoroethylene and hexafluoropropylene [116-15 ] under separate processing conditions. Dechlorination of CFC-113 forms chlorotrifluoroethylene [79-38-9]. Vinyhdene fluoride [75-38-7] is produced by the thermal cracking of HCFC-142b. 

Prepa.ra.tlon There are five methods for the preparation of long-chain perfluorinated carboxyUc acids and derivatives electrochemical fluorination, direct fluorination, telomerization of tetrafluoroethylene, oligomerization of hexafluoropropylene oxide, and photooxidation of tetrafluoroethylene and hexafluoropropylene. 

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. 

Materials compatibility. We use scrupulously clean and scratch-free FEP (FEP is the acronym for the copolymer of tetrafluoroethylene and hexafluoropropylene) tubing for handling our mixtures of fluorine and nitrogen at ambient temperature. Corrugated FEP tubing is convenient for making strain-free assemblies. We have found that Monel is excellent for use with dry molten KF-2HF. Mild steel corrodes slowly and stainless steels corrode rapidly. Kel-F polychlorotrifluoroethylene is satisfactory for use with HF and with KF-2HF polypropylene and polymethylpentene are not satisfactory. 

The processability of fluorine-containing polymers is improved by replacement of one or more of the fluorine atoms. Replacing one of the eight fluorine atoms with a trifluoromethyl group gives a product called FEP or Viton, actually a copolymer of tetrafluoroethylene and hexafluoropropylene (Equation 6.53). Polytrifluoromonochloroethylene (PCTFE, Kel F) (Equation 6.54), in which one fluorine atom has been replaced by a chlorine atom, has a less regular structure and is thus more easily processed. Poly(vinylidene fluoride) (PVDF, Kynar) (Equation 6.55) is also more easily processable but less resistant to solvents and corrosives. 

Teflon. The Teflon TFE polymer is prepared from tetrafluoroethylene by Du Pont it is white and nearly opaque except in thin sheets. Teflon FEP is a copolymer of tetrafluoroethylene and hexafluoropropylene, which is more readily molded and is translucent. The FEP polymer has more limited chemical... 

Several plastics, with high resistance to chemical attack and high temperatures, deserve special mention for process designers of inherently safer plants. For example, tetrafluoroethylene (TFE), commonly called Teflon brand TFE, is practically unaffected by all alkalies and acids except fluorine and chlorine gas at elevated temperatures, and molten metals. It retains its properties at temperatures up to 260°C. Other plastics that have similarly excellent properties (but are different enough that they each have their niche) include chlorotrifluoroethylene (CTFE) Teflon FEP, a copolymer of tetrafluoroethylene and hexafluoropropylene polyvinylidene fluoride (PVF2) (also... 

Crystallinity of never-melted PTFE is in the range of 92-98%, consistent with an unbranched chain structure while FEP, a copolymer of tetrafluoroethylene and hexafluoropropylene, has an as-polymerized crystallinity of 40-50%. In FEP, the pendent CF3 group is bonded to a tertiary carbon that is less thermally stable than primary and secondary carbon atoms. Degradation curves (Fig. 3) indicate degradation onset temperatures of 300°C for FEP (0.02% weight loss) and 425°C for PTFE (0.03%i weight loss). 

Polytetrafluoroethylene (PTFE Teflon) was discovered accidently by PlunkettCZ nd commercialized by DuPont in the 1940 s. This polymer has a solubility parameter of about 6H and a high melting point of 327°C and is not readily moldable. Poly-chlorotrifluoroethylene (CTFE, Kel-F), the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF, Kynar), the copolymer of tetrafluoroethylene and ethylene (ETFE), the copolymer of vinylidene fluoride and hexafluoroisobutylene (CM-1), perfluoroalkoxyethylene (PFA) and polyvinyl fluoride (PVF, Tedlar) are all more readily processed than PTFE. However, the lubricity and chemical resistance of these fluoropolymers is less than that of PTFE. 

Vega and English [13] obtained F spectra and relaxation times for static samples of a copolymer of tetrafluoroethylene and hexafluoropropylene (TFE-co-HFP 85 mol% HFP) by the multiple-pulse technique (MREV8) at various temperatures (see Fig. 18.19). They observed CF2 group lineshapes in crystalline and amorphous regions, and also CF3 and CF lineshapes. After subtracting the crystalline contribution to obtain the amorphous lineshape, the latter contribution was analysed as a function of temperature to obtain information about the type of molecular motion present. The )8 and y relax-... 

Fluorinated ethylene propylene (FEP) is produced by copolymerization of tetrafluoroethylene and hexafluoropropylene, and consists of predominantly linear chains. 

Figure 14-2. The relationship between the refractive index d for the sodium D line (589.3 nm) and the Abbe dispersion v for various polymers [see Equation (14-12)]. PVCz, poly(A-vinyl carbazole) P(TFE-HFP), copolymer of tetrafluoroethylene and hexafluoropropylene. For other abbreviations, see Table VII-6, Appendix.

Chem. Descrip. FEP resin (copolymer of tetrafluoroethylene and hexafluoropropylene)... 

Peduoropolyethers, which constitute special class of fluoropolymer, are useful as lubricants, elastomers, and heat-transfer fluids under demanding conditions. Several commerical products are available, which are generally prepared by ring-opening polymerization of hexafluoropropylene oxide or by the random copolymerization of tetrafluoroethylene and hexafluoropropylene with oxygen under ultraviolet irradiation. Direct fluorination of hydrocarbon ethers has been reported but must be done very slowly under earefidly eontrolled... 

Teflon FEP Copolymer from tetrafluoroethylene and hexafluoropropylene Du Pont, U.S. 

Copolymers. Fluorinated ethylene propylene (FEP) is a copolymer of tetrafluoroethylene and hexafluoropropylene. It has properties similar to PTFE but with a melt viscosity suitable for molding with conventional toermoplastic processing techniques. The improved processabUity is obtained by replacing one of the fluorine groups on PTFE with a trifluoromethyl group as shown in Fig. 2.4. ... 

Fig. 10. True stress-true strain behavior of polymers. Delrin is an acetal resin Lexan, a polycarbonate Teflon TFE designates the tetrafluoroethylene homopolymer Teflon FEP is a copolymer of tetrafluoroethylene and hexafluoropropylene (17). To convert MPa to psi, multiply by 145. Courtesy of Polymer Engineering and Science.

Fluoropolymers are unique amongst polymers in respect of their chemical and thermal stability, biocompatibility, water resistance and superb dielectric properties, having a dielectric constant of 2.1. Other members of the Teflon family include a polymer of tetrafluoroethylene and hexafluoropropylene (FEP) and a polymer of tetrafluoroethylene and perfluorovinylether (PEA). The 327 °C melting point of PTFE is reputed to be one of the highest in organic polymer chemistry. The melting points of FEP and PEA are 260 C and 305 °C, respectively. 

Fluorinated Ethylene-Propylene Resin (FEP, PFEP) This member of the fluorocarbon family is a copolymer of tetrafluoroethylene and hexafluoropropylene, possessing most of the desirable properties of PTFE, yet truly meltable and, therefore, processable in conventional extrusion and injection-molding equipment. It is available in pellet form for those operations and as dispersions for spraying and dipping. 

Teflon FEP n Copolymer from tetrafluoroethylene and hexafluoropropylene, manufactured by DuPont. 

The aqueous dispersion was coagulated by agitation until a particulate coagulum was obtained which was then separated from water by filtration, rinsed with water, and dried. The dry powder was spread on aluminum trays to a depth of 5 cm and heated for 3 hours at 350°C. The product was a mass of copolymer of tetrafluoroethylene and hexafluoropropylene. It had a melting point of280°C, melt viscosity of 7 x 10" poise. A sample of FEP was chopped into small pieces and... 

Continuous polymerization of tetrafluoroethylene and hexafluoropropylene by bulk polymerization has also been reported. The process of this patent requires relatively high pressure (41-690 MPa) and temperature (200-400°C). These reaction conditions are quite severe compared to those used for batch polymerization. This patent discloses an amorphous polymer consisting of three comonomers, for example ... 

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