PTFE and FEP

Fig. 3 A comparison of thermal degradation of FEP and PTFE in air. (From Ref " l) (View this art in color at www.dekker.com.)...

Figure 3.76 Creep behavior of PVDF, FEP, and PTFE in tensile mode at 23°C.i >...

The radiation grafting of TFS onto various fluorine-containing base polymers, such as LDPE, ETFE, PEA, FEP, and PTFE has been accomphshed by the pre-irradiation method [105]. A proper examination of the swelling properties and solubility parameters of these polymer films in pure TFS showed that LDPE yielded the highest, and PTFE led to the lowest graft levels. This is because of the fact that the sorption of hquid in polymer depends on the affinity between the hquid and the polymer film. 

Mechanical Properties. Table 2 shows the physical properties of Teflon PFA (28,29). At 20-25°C the mechanical properties of PFA, FEP, and PTFE are similar differences between PFA and FEP become significant as the temperature is increased. The latter should not be used above 200°C, whereas PFA can be used up to 260°C. Tests at liquid nitrogen temperature indicate that PFA performs well in cryogenic applications (Table 3). 

Fluoroplastics are, generally, slippery materials with smooth surfaces due to their low coefficients of friction. The coefficient of friction decreases with an increase in fluorine content. Numerous mechanical applications depend on low friction of these plastics with little or no lubrication. In the case of perfluoroplastics, such as PFA, FEP, and PTFE, dynamic coefficient of friction is larger than static coefficient of friction. It... 

The change in the surface of the treated fluoro-plastics is also reflected in the contact angle. For example, water contact angle of FEP and PTFE decreases from 109° to 52° (advancing) upon sodium/ammonia treatment. Heating the treated fluoropolymer for a... 

FEP polymer is a linear and random copolymer of TFE and hexafluoropro-pylene (HFP) containing -CF CF and -CF CF(CFj)— units in its structure. FEP and PTFE polymers are structurally similar except that FEP polymer contains trifluoromethyl pendant groups on its main chain as shown below. 

Like other perfluoropolymers. Teflon PFA is not highly resistant to radiation (30). Radiation resistance is improved in vacuum, and strength and elongation ate increased more after low dosages (up to 30 kGy or 3 Mrad) than with FEP or PTEE. Teflon PEA approaches the performance of PTEE between 30 and 100 kGy (3—10 Mrad) and embrittles above 100 kGy (10 Mtads). At 500 kGy (50 Mrad) PTFE, FEP, and PFA ate degraded. The effect of radiation on tensile strength and elongation is shown in Table 7. 

Polyester (PETP, PBTP) Fluorocarbons (PTFE, PFA, FEP and ETFE)... 

As for all plastics, the costs fluctuate greatly with the crude oil price, and are only given to provide a general idea. They are generally of the order of ten or a few tens of Euros per kilogram for PTFE, twice as much as PTFE for FEP and three times as much as PTFE for PEA. 

The global consumption is roughly estimated at 70000 t/year, mainly in industrial and electrical electronics applications. FEP and PEA consumptions are, perhaps, ten times inferior to that of PTFE. 

PTFE, FEP and PEA are sensitive to high-energy radiation. Exposure to 1 Mrad can lead to a measurable degradation. 

PTFE, FEP and PFA are attacked only by alkaline metals and their organic derivatives elemental fluorine and chlorine trifluoride alkali and alkaline earth metals with their oxides and carbonates above 350°C. The other halogens, aqua regia, nitrosulfuric acid mixtures, oleum (fuming sulfuric acid) and solvents are without significant effects. 

Gluing is very difficult for PTFE, FEP and PEA, needing surface treatment by alkaline metal derivatives. The assembly can be tough but chemical and thermal resistances are weakened. 

D. Fluorocarbon Polymers. Four different fluorocarbons account for the bulk of the laboratory applications polytetrafluoroethylene, Teflon PTFE po-ly(chlorotrifluoroethylene), KEL-F tetrafluoroethylene-hexafluoropropylene copolymer, Teflon FEP and tetrafluoroethylene-perfluorovinyl ether copolymer, PFA. These polymers are inert with most chemicals and solvents at room temperature and exceptionally inert with oxidizing agents. They also have an exceptional resistance to temperature extremes. However, they are decomposed by liquid alkali metals, solutions of these metals in liquid ammonia, and carban-ion reagents such as butyllithium. Teflon retains some of its compliance at liquid hydrogen temperature. The maximum temperature which is recommended for continuous service is 260°C for Teflon PTFE and PFA, and about 200°C for Kel-F and Teflon FEP. 

Figures 7a, b, and c show the SIMS spectra of known polymers PTFE, FEP, and PVF2. Briggs and Wootton (13) report that radiation from electron beam charge neutralization...

ETFE, a copolymer of TFE and ethylene, has a higher tensile strength than PTFE, FEP, and PFA because its molecular chains adopt a planar zigzag configuration.5 A strong electronic interaction between the bulky CF2 groups of one chain and the smaller CH2 groups of an adjacent chain causes an extremely low creep.6... 

Fabrics coated with FEP and PFA can be laminated and heat-sealed into protective garments, canopies, etc. FEP-coated polyimide films are used in electronics and as a wire tape. FEP-based anticorrosion coatings are used in the chemical industry and as chemical barriers.18 A thin coating of FEP or PFA can be used as a hot melt adhesive for a variety of substrates, including PTFE-coated fabrics and laminates. 

With fluorosulfonate ionomers other than Nation, the specifications for the GDL has to be changed. More recently, Nishikawa et al. [79] developed GDLs for novel organic-inorganic hybrid electrolytes. They mixed Triton and PTFE dispersions with carbon black and coated the mixture on to carbon paper that had been wet-proofed with FEP copolymer. A nanohybrid electrolyte was prepared by a sol-gel method and formed over the GDL. Addition of uncatalyzed carbon black to the cathode GDL was found to enhance the performance at high current densities. 

This kind of contamination was carefully evaluated by using various labware glass and quartz tubes, polytetrafluoroethylene (PTFE) vessels, fluorinated ethylene propylene (FEP) and perfluoroalkoxy (PFA) tubes. Ideally, all trace element determinations should be carried out in clean rooms in which the incoming air is filtered and special clothing is worn. 

Standard specification for contact-molded FRP chemical-resistant tanks Standard specification for PTFE PFA FEP- and ETFE-lined piping Standard specification for PE and polypropylene (PP) plastic-lined ferrous metal pipe and fittings... 

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