Hydrofluorocarbons

Hydrofluoric acids Hydrofluoroboric acid Hydrofluorocarbon Hydrofluorocarbons... 

Sprays. Aerosol spray emulsions are of the water-in-oil type. The preferred propellant is a hydrocarbon or mixed hydrocarbon—hydrofluorocarbon. About 25 to 30% propellent, miscible with the oil, remains in the external phase of the emulsion. When this system is dispensed, the propellant vaporizes, leaving behind droplets of the w/o emulsion (Fig. 2b). A vapor tap valve, which tends to produce finely dispersed particles, is employed. Because the propellant and the product concentrate tend to separate on standing, products formulated using this system, such as pesticides and room deodorants, must be shaken before use. 

The 1990 Clean Air Act regulates the production and use of CFCs, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbon (HFC) substitutes. CFC and halon (Class I substances) usage is to be phased out in steps until total phaseout occurs on January 1,... 

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs. 

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. 

The physical properties of hydrofluorocarbons reflect their polar character, and possibly the importance of intermolecular hydrogen bonding (3). Hydrofluorocarbons often bod higher than either their PFC or hydrocarbon counterparts. For example, l-C H F bods at 91.5°C compared with 58°C for n-Q and 69°C for Within the series of fluorinated methanes, the boiling point reaches a maximum for CH2F2, which contains an equal... 

Table 2. Physical Properties of Aliphatic Hydrofluorocarbons (HFCs) ...

Hydrofluorocarbons are also prepared from acetylene or olefins and hydrogen fluoride (3), or from chlorocarbons and anhydrous hydrogen fluoride in the presence of various catalysts (3,15). A commercial synthesis of 1,1-difluoroethane, a CFG alternative and an intermediate to vinyl fluoride, is conducted in the vapor phase over an aluminum fluoride catalyst. 

The direct chlorination of hydrofluorocarbons and fluoroolefins has also been used commercially, eg, in the preparations of CH2CCIF2 from CH2CHF2 and CCIF2CCIF2 from tetrafluoroethylene. 

Hydrofluorocarbons generally are less toxic than HGFGs, with the notable exception of HFG-152, GH2FGH2F, which apparently can be metabohcaHy converted to monofluoroacetic acid and is therefore quite toxic (44). 

A leader in the refrigerants industry, we manufacture and supply customers with economical chlorofluorocarbon (CFC) replacements and non-ozone depleting hydrofluorocarbon (HFC) refrigerants for automotive, home, commercial and transportation uses. In the Americas and Asia, you can find these products under the Genetron name and in Europe and the Middle East under Honeywell Refrigerants. 

As you know, most countries are phasing out certain refrigerants to lessen damage to the ozone layer. The chemicals being phased out are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Replacements are hydrofluorocarbons (HFCs) and certain blends. The DuPont web site (www.dupont.com) gives the handy Table I of recommended replacement refrigerants for various applications. 

Ruorocarbon solvent polarity (PJ increases when fluonne is substituted by chlonne or hydrogen, and hydrofluorocarbons can be more polar than their hydrocarbon analogues Notably, = 7 52 and P (1,2 C H4p2) = 7 86 vs... 

The cap is the percentage of the calculated level of chlorofluorocarbons consumed in the base year plus the calculated level of hydrofluorocarbons consumed the same base year It applies only to HCFCs Calculated in the context means that the amount of each substance is adjusted by its ozone depletion potential (ODP), a measure of its potential to deplete stratosphenc ozone relative to that of CFC 11... 

Refngeration technology is moving into a new phase with the introduction of hydrofluorocarbons that combme the safety of chlorofluorocarbons with a much lower environmental impact The considerable care bemg taken to choose the new refngerants under the close scrutmy of the public and regulatory bodies will ensure that the new products wiU benefit mankind for years to come... 

Hexamethylphosphoramide (HMPT), 185 HFBPA-based poly(arylene ether)s, 362 HFCs. See Hydrofluorocarbons (HFCs) High-impact polystyrene (HIPS), 219 High-melting polymers, 33 High-melting-point fiber-forming polyesters, 19... 

Organic Fluorides. X. The Formation of Fluoro-oils and Resins by the Polymerisation of Hydrofluorocarbons with Fluorine," F. Smith, M. Stacey, J. C. Tatlow, and (in part) J. K. Dawson, and B. R. J. Thomas,/ Appl. Chem., 2 (1952) 97-105. 

Standley LJ, TL Bott (1998) Trifluoroacetate, an atmospheric breakdown product of hydrofluorocarbon refrigerants biomolecular fate in aquatic organisms. Environ Sci Technol 32 469-475. 

Wallington TJ, OJ Nielsen (2002) Atmospberic chemistry and environmental impact of hydrofluorocarbons (HFCs) and hydrofluoroethers (HFEs). Handbook Environ Chem 3N 85-102. 

Acronyms for chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (MFCs)... 

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