DuPont’s Teflon

For duPont s Teflon tube (Vr-in. diameter) heat exchangers (Figure 10-8) for condensing, heating, and cooling service, the U values range from 15-35. Little or no fouling occurs on the Teflon surface. 

Shock-resistant, flexible hose (Figure 40.32) assemblies are required to absorb the movements of mounted equipment under both normal operating conditions and extreme conditions. They are also used for their noiseattenuating properties and to connect moving parts of certain equipment. The two basic hose types are synthetic rubber and polytetrafluoroethylene (PTFE), such as DuPont s Teflon fluorocarbon resin. 

Of all the elements, fluorine is the most reactive and the most electronegative (a measure of tendency to acquire electrons). In its chemically combined form, it always has an oxidation number of -1. Fluorine has numerous industrial uses, such as the manufacture of UF6, a gas used to enrich uranium in its fissionable isotope, uranium-235. Fluorine is used to manufacture uranium hexafluoride, SF6, a dielectric material contained in some electrical and electronic apparatus. A number of organic compounds contain fluorine, particularly the chlorofluorocarbons used as refrigerants and organofluorine polymers, such as DuPont s Teflon. 

Halar is a tradename of the Allied Corporation, Morristown, NJ, for their polytetra-fluoroethylene sheet (similar material to duPont s Teflon ). Allied markets this sheet through its own sales force. 

A. Cortese, DuPont s Teflon Dilemma, Chief Executive, November 1, 2003, p. 22. Available at factiva database. 

Oxirane formation can also occur via free radical mechanisms, as in the reaction of certain fluoroalkenes with oxygen. Under pressure at elevated temperatures, oxygen alone can suffice, but activation is frequently provided in the form of radical initiators (e.g., tribromofluoromethane) and ultraviolet light. Thermolysis of dioxole 5, comonomer from which DuPont s Teflon-AF is made, offers an unusual route to an oxirane. Rearrangement of the heterocycle presumably takes place via a biradical intermediate. ... 

Once a carbon membrane of high performance is produced, the effect of exposure to water vapor must be considered. It has been reported that the selectivity of a typical membrane decreases as the amount of sorbed water increases [38]. Not many studies have taken into accoimt this phenomenon very seriously, although it becomes quite important when a carbon membrane is commercialized. This is primarily due to the fact that water vapor can be foimd in a large number of process stream [38]. To date, only Jones and Koros [39, 40] have studied this phenomenon in detail, and they proposed the use of composite membranes (coated DuPont s Teflon AF1600 and AF2400) as a solution to this drawback. On the other hand, the humidity found in the ambient atmosphere can also have an adverse effect on carbon membrane performance. Therefore, the study of storage conditions for carbon membranes is also an important consideration for carbon membrane research in the future. 

Considered next are self-lubricated plastic materials, namely fluorocarbon resins, fabrics, and coatings. Dupont s Teflon, the thermoplastic PTFE, has a low coefficient of friction, p, and a large temperature range from -450°F to -e5(X)°F. The PlFF types are the most common and are available in sheet rod or film. Perfluoro alkoxy alkane (PFA) resins have comparable properties to PTFE. Another fluotinated ethylene propylene is a copolymer, that is, easier to mold, but it has a higher coefficient of fiiction p, and a temperature limit of 390°F. 

Poly(tetrafluoroethylene) (PTFE), which is also known by DuPont s trade-name Teflon, is a solid at room temperature and has a dielectric constant in the range of 2.00-2.08, while its monomer, tetrafluoroethylene, is a gas at room temperature. PTFE is exceptionally chemically inert, has excellent electrical properties and outstanding stability, and retains its mechanical properties at high temperatures. The problem with PTFE is that it is not processable. A family of commercial polymeric materials known as Teflon AF is believed to be a... 

However, Plunkett s first reaction, and that of his technician, was one of frustration, because it would mean that they would have to start their experiment all over again. They didn t quite realize what they had But Plunkett was aware that the TFE had somehow polymerized. With 20/20 hindsight, given that Plunkett worked for a company that was at the forefront of polymer synthesis, he should have perhaps predicted that the polymerization of TFE was possible, if not likely. Frankly, Plunkett and Rebok were bloody lucky that they were not blown to bits Within a few weeks of laboratory testing, PTFE was found to be inert to all the solvents, acids and bases available. It was then quickly established by DuPont s polymer chemists that TFE could be free radically polymerized in water. Plunkett s discovery is legendary and for the 50th anniversary of the discovery of Teflon , DuPont established the Plunkett Award in his honor, for innovative applications of this unique material. 

Teflon DuPont s tradename for its family of polytetra-fluoroethylene plastics. 

General Description Fluorinated ethylene propylene (FEP), a melt-processable fluorocarbon, is a copolymer of tetrafluoroethylene (TFE) and hexafluo-ropropylene. Fluorinated ethylene propylene and TFE yield similar properties, with the exception ofTFE s lowermelt viscosity.fl 1 DuPont s high-performance material Teflon FEP film is a transparent, thermoplastic film.P ... 

Mechanical properties are retained up to 200°C, even in continuous service, which is better than with most plastics. At high temperatures, these copolymers react with fluorine, fluorinating agents, and molten alkali metals. They are commercially available under the DuPont trademark Teflon FEP fluorocarbon resin. A similar product is manufactured by Daikin Kogyo and Dyneon and sold under the trademarks Neoflon and Hostaflon, respectively. The People s Republic of China... 

Manufacturers of PTFE include Daikin Kogyo (Polyfion), DuPont (Teflon), Dyneon, Asahi Glass, Ausimont (Algoflon and Halon), and the CIS (Fluoroplast). India and The People s Republic of China also manufacture some PTFE products. Additional information on specific manufacturers products can often be obtained by consulting their internet web sites (for example, www.dupont.com/teflon). 

Details Plunkett accidentally discovered polymerization in experiment of production of new refrigerant (iron of container acted as a catalyst of polymerization) DuPont coined Teflon s name in 1945 and initiated industrial production in 1946 the first teflon-coated frying-pan was produced in 1961 by Marion Trozzolo ... 

The success of DuPont s Nafion spurred the development of other polymeric materials with similar chemical architecture. The most notable material developments have been the Dow experimental membrane (Dow Chemicals), Flemion (Asahi Glass), Aciplex (Asahi Kasei), as well as Hyflon Ion and its most recent modification Aquivion (SolviCore). In addition to excellent ionic conductivity, materials of the PFSA family, illustrated in Figure 2.2, exhibit exceptional stability and durability in highly corrosive acidic environments, owing to their Teflon-like backbone (Yang et al., 2008 Yoshitake and Watakabe, 2008). 

Table 6.24. Dimensional Characteristics and Properties of Teflon FEP Films made by DuPont S ...

Abstract There have been numerous studies on modifying DuPont s Nafion (a perfluorosulfonic acid polymer) in order to improve the performance of this membrane material in a direct methanol fuel cell. Modifications focused on making Nafion a better methanol barrier, without sacrificing proton conductivity, so that methanol crossover during fuel cell operation is minimized. In this chapter, a brief literature survey of such modifications is presented, along with recent experimental results (membrane properties and fuel cell performance curves) for (1) thick Nafion films, (2) Nafion blended with Teflon-FEP or Teflon-PFA, and (3) Nafion doped with polybenzimidazole. 

Copper foil is adhered to polyester film based flexible circuitry with a thermoplastic polyester adhesive. This produces a bond having lower operating temperature than the other adhesives cited. When polyimide film such as DuPont s Kapton is used as the high temperature flexible circuit substrate, a thermoplastic FEP Teflon coating or epoxy, acrylic, or polyimide adhesive is used to bond the foil. 

Typically, composite electrodes are employed. The electrodes are composed of high-surface-area carbon powders mixed with a catalyst and Teflon (DuPont s registered trademark for polytetrafluoroethylene) and laminated with a current collector made of expanded metal mesh. The use of the Teflon binder in the air... 

Although many fluorocarbon polymers are commercially available (Appendix 16.H), poly(tetrafluoroethylene) (PTFE) is estimated to command about 90% of the market. This polymer, under DuPont s trade name. Teflon, has been made since the early 1940s. Both PTFE and poly(chlorotrifluoroethylene) were developed to meet wartime demands, especially for the corrosive processes involving separation of radioactive isotopes. Many other fluorinated polymers have been commercialized over the years. 

The four suppHers to the U.S. market ate DuPont, 3M, Ausimont, and Daiken. It is estimated that 7000—8000 t/yr ate used in the United States and growing rapidly. In addition DuPont and Daiken seU what in essence ate elastomeric Teflons under the respective trade names of Kalte2 and Chemta2. 

Wallace Carothers and coworkers at DuPont synthesized aliphatic polyesters in the 1930s [Furukawa, 1998 Hounshell and Smith, 1988]. These had melting points below 100°C, which made them unsuitable for firber use. Carothers then turned successfully to polyamides, based on the theoretical consideration that amides melt higher than esters. Polyamides were the first synthetic fibers to be produced commercially. The polyester and polyamide research at DuPont had a major impact on all of polymer science. Carothers laid the foundation for much of our understanding of how to synthesize polymeric materials. Out of that work came other discoveries in the late 1930s, including neoprene, an elastomer produced from chloro-prene, and Teflon, produced from tetrafluoroethylene. The initial commercial application for nylon 6/6 was women s hosiery, but this was short-lived with the intrusion of World War II. The entire nylon 6/6 production was allocated to the war effort in applications for parachutes, tire cord, sewing thread, and rope. The civilian applications for nylon products burst forth and expanded rapidly after the war. 

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