Fluoropolymer

Electromagnetic flow meters ate avadable with various liner and electrode materials. Liner and electrode selection is governed by the corrosion characteristics of the Hquid. Eor corrosive chemicals, fluoropolymer or ceramic liners and noble metal electrodes are commonly used polyurethane or mbber and stainless steel electrodes are often used for abrasive slurries. Some fluids tend to form an insulating coating on the electrodes introducing errors or loss of signal. To overcome this problem, specially shaped electrodes are avadable that extend into the flow stream and tend to self-clean. In another approach, the electrodes are periodically vibrated at ultrasonic frequencies. 

Ausimont SpA Milan, Italy SFg, fluoropolymer fluids, fluoromonomers, F2 gas large... 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

High temperature resistance of ETEE and other fluoropolymers ia automotive fuels and their permeation resistance have been discussed (28,29). 

Stripes may be appHed to wire coated with ETEE fluoropolymer over DuLite 817-5002 fluoropolymer clear enamel or other bases. Thermally stable pigments are required. Stripes may be appHed by gravure-wheel-type appHcators and oven-cured in-line. 

The success of many appHcations depends on the abiHty of ETEE fluoropolymer to be economically assembled. 

The Du Pont HaskeU Laboratory for Toxicology and Industrial Medicine has conducted a study to determine the acute inhalation toxicity of fumes evolved from Tefzel fluoropolymers when heated at elevated temperatures. Rats were exposed to decomposition products of Tefzel for 4 h at various temperatures. The approximate lethal temperature (ALT) for Tefzel resins was deterrnined to be 335—350°C. AH rats survived exposure to pyrolysis products from Tefzel heated to 300°C for this time period. At the ALT level, death was from pulmonary edema carbon monoxide poisoning was probably a contributing factor. Hydrolyzable fluoride was present in the pyrolysis products, with concentration dependent on temperature. 

Technical Information, No. 11, Processing Guidelinesfor Du Pont Fluoropolymer Fotocasting Powders ofTef l and Teflon PFA, E. I. du Pont de Nemours Co., Inc., Wilmington, Del., 1982. 

Because of its excekent combination of properties, processibkity, and relatively low price compared to other fluoropolymers, PVDF has become the largest volume fluoropolymer after PTFE consumption in the United States has grown from zero in 1960 to about 6200 metric tons in 1991 (186). About 49% of the consumed volume is PVDF modified by copolymerization with 5—12-wt % HFP to enhance flexibkity. In 1992, Hst price for homopolymer powders was 15.32/kg, and for pekets 15.42/kg the reported market price was 14.09—14.22/kg (187). In the United States, almost ak PVDF is suppHed by Ausimont USA, Inc., Elf Atochem North America, Inc., and Solvay Polymers, Inc. Ausimont and Elf Atochem are producers Solvay is an importer of the resin. Smak amounts of resin are imported from Germany by Huls America, Inc, and from Japan by Kureha Chemical Industry Co., Ltd. PVDE producers and their trademarks are Hsted in Table 4. 

After 10 years of unabated rapid growth in the plenum wire and cable market, fluoropolymers including PVDE, primarily the flexible VDE/HEP copolymer, are beginning to lose market share to lower priced PVC-akoys. The loss of market share in the plenum market probably wkl be compensated by growth of PVDE in other fields thus during the mid-1990s the total volume of PVDE may not grow (188). 

Other sources of by-product HCl include allyl chloride, chlorobenzenes, chlorinated paraffins, linear alkylbenzene, siHcone fluids and elastomers, magnesium, fluoropolymers, chlorotoluenes, benzyl chloride, potassium sulfate, and agricultural chemicals. 

The PVC formulations shown in Table 2 represent typical compounds used by the wine and cable industry. PVC compounders have developed new PVC-based formulations with very good fire and smoke properties (can pass the UL 910 Steiner Tunnel test) that compete with the more expensive fluoropolymers. These can be used in fabricating telecommunication cables usable for plenum area appHcations. 

Examples of thermoplastic coatings an fluoropolymers, eg. Teflon or polyamides, eg, nylon. Thermosetting coatings are more resistant to ... 

Commonly used materials for cable insulation are poly(vinyl chloride) (PVC) compounds, polyamides, polyethylenes, polypropylenes, polyurethanes, and fluoropolymers. PVC compounds possess high dielectric and mechanical strength, flexibiUty, and resistance to flame, water, and abrasion. Polyethylene and polypropylene are used for high speed appHcations that require a low dielectric constant and low loss tangent. At low temperatures, these materials are stiff but bendable without breaking. They are also resistant to moisture, chemical attack, heat, and abrasion. Table 14 gives the mechanical and electrical properties of materials used for cable insulation. 

The anode and cathode chambers are separated by a cation-permeable fluoropolymer-based membrane (see Membrane technology). Platinum-electroplated high surface area electrodes sold under the trade name of TySAR (Olin) (85,86) were used as the anode the cathode was formed from a two-layer HasteUoy (Cabot Corp.) C-22-mesh stmcture having a fine outer 60-mesh stmcture supported on a coarse inner mesh layer welded to a backplate. The cell voltage was 3.3 V at 8 kA/m, resulting ia a 40% current efficiency. The steady-state perchloric acid concentration was about 21% by weight. 

Among the preformed polymers cured by minor additions of aHyl ester monomers and catalysts followed by heat or irradiation are PVC cured by diallyl fumarate (82), PVC cured by diallyl sebacate (83), fluoropolymers cured by triaHyl trimeUitate (84), and ABS copolymers cured by triaUyl trimeUitate (85). 

Core technical competencies may be composed of a number of core or key technologies. The competencies in turn can support product families, platforms, or core products, which then support individual products. These products may ultimately be found in a number of forms or shapes. For example, a key technology such as polymer characterization may support a competency in polymer synthesis and architecture, which in turn supports the platform of fluoropolymers and the product family of Teflon (DuPont) fluoropolymer resins that can be found as films, fibers, or in other forms. 

Chrome-complexed fluorochemicals, as weU as fluoropolymers, are widely used products. The compositions are proprietary. Fluorochemicals provide a high degree of water repeUency as weU as repeUency to aqueous stains, oUs, grease, and oilhorne stains. TraditionaUy, treatments are appUed duting a dmm process ia which about 30 min are required for flUl penetration of the leather to occur. Products are also avaUable for appUcation with sprayiag equipment and roU coaters. 

OU- and water-resistant treatments have been reported which iavolve blends of fluoropolymers and alkoxysUane or alkoxysUoxane materials, dehvered as 100% actives (90) or from solvent or emulsion (91), fluotinated alkoxysUoxane emulsions (92), and self-emulsifying fluotinated alkoxysUane-based concentrates (93). 

Materials of Construction. Glass has excellent corrosion-resistance to wet or dry bromine. Lead is very usefiil for bromine service if water is less than 70 ppm. The bromine corrosion rate increases with concentrations of water and organics. Tantalum and niobium have excellent corrosion-resistance to wet or dry bromine. Nickel has usefiil resistance for dry bromine but is rapidly attacked by wet bromine. The fluoropolymers Kynar, Halar, and Teflon are highly resistant to bromine but are somewhat permeable. The rate depends on temperature, pressure, and stmcture (density) of fluoropolymer (63). 

Electrical Applications. Plastics are used for electrical insulation, conduit and enclosures, lighting fixtures, and mechanical devices. The most widely used plastic for wire and cable insulation is flexible, plasticized PVC, which constitutes well over half the market in insulating wires for buildings, automobiles, appHances, and power and control lines. Polyethylene is also a factor. Higher performance plastics such as nylon and fluoropolymers also play a smaller role in this area. 

This high projected growth rate is driven by the expected strong growth of the HCFC-22 and fluoropolymer markets, which account for 90% of the total chloroform market. HCFC-22 is a substitute for some apphcations currendy using CFC-11 and CFC-12. It is restricted by the Montreal Protocol but will not be phased out until much later. This demand pushed chloroform production up 10% in both 1988 and 1989 (32). 

About 90% of the chloroform produced goes into the production of HCFC-22 (chlorodifluoromethane [75-45-6]). Of this 90% about 70% is used as a refrigerant and about 30% is used as a starting material in the production of fluoropolymers, such as polytetrafluoroethylene (PTFE). Of the remaining 10% of the chloroform production about 8% is exported and 2% is used in other ways. 

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