Fluorocarbons chemical inertness

Chemically Resistant Fibers. Fibers with exceUent chemical resistance to corrosive and/or chemical warfare agents or extreme pH conditions (eg, very acidic or very alkaline) were initially used for protective clothing. However, appHcations for filtration of gases and Hquids in numerous industrial faciHties are now the more important. For example, PPS is suitable for use in filter fabrics for coal-fired boilers because of its outstanding chemical and heat resistance to acidic flue gases and its exceUent durabUity under these end use conditions. Many high tenacity fibers are also chemically inert or relatively unaffected under a variety of conditions. Aramids, gel spun polyethylene, polypropylene, fluorocarbon, and carbon fibers meet these criteria and have been used or are being considered for appHcations where chemical resistance is important. 

HalogenatedFluids. Chlorocarbons, fluorocarbons, or combinations of the two are used to form lubricating fluids (see Chlorocarbons and CHLOROHYDROCARBONS Fluorine COMPOUNDS, ORGANIC). Generally, these fluids are chemically inert, essentially nonflammable, and often show excellent resistance to solvents. Some have outstanding thermal and oxidation stability, because they are completely unreactive even in Hquid oxygen, and extremely low volatility. 

To appreciate the significance of these two new compounds one must recall the striking properties of carbon compounds in which hydrogen is completely replaced by fluorine. The products are characterized by great chemical inertness, but have physical properties which are similar in many respects to those of the hydrocarbons. This is illustrated by the following summary (Table 3) of the boiling points of fluorocarbons and hydrocarbons of the two series C F2 +2 and... 

Polyethylenes, fluorocarbons (Teflon and Kel-F) and chlorosulfonated polyethylene (Hypalon) are not affected by contact with explosives and propellants because of their chemical inertness. 

Compounds with a high LUMO and a low HOMO (Figure 5.5a) will be chemically inert. Saturated hydrocarbons, fluorocarbons, and to some extent ethers fall in this category. 

In 1938, while attempting to prepare fluorocarbon derivatives, Roy J. Plunkett, at DuPont s Jackson Laboratory, discovered that he had prepared a new polymeric material. The discovery was somewhat serendipitous as the TFE that had been produced and stored in cylinders had polymerized into poly(tetra-fluoroethylene) (PTFE), as shown in Eigure 4.2. It did not take long to discover that PTFE possessed properties that were unusual and unlike those of similar hydrocarbon polymers. These properties include (1) low surface tension, (2) high Tm, (3) chemical inertness, and (4) low coefficient of friction. All of these properties have been exploited in the fabrication of engineering materials, wliich explains the huge commercial success of PTFE. 

FLUOROCARBON. A number of organic compounds analogous to hydrocarbons, in which the hydrogen atoms have been replaced by fluorine. The term is loosely used to include fluorocarbons that contain chlorine these should property be called chlorofluorocarbons or fluorocarbon chlorides, since ii is these which arc though) to deplete the ozone layer or (he upper atmosphere. Fluorocarbons are chemically inert, nonflammable, and stable to heat up to 260-3l6°C. They are denser and more volatile lhan the corresponding hydrocarbons, and have low refractive indices, low-dielectric constants, low solubilities, low surface tensions, and viscosities comparable to hydrocarbons. Some arc compressed gases others are... 

The almost universal chemical inertness of polytetrafluoroethylene has been attributed to the strength of the carbon-fluorine bond and the way in which the fluorine atoms protect the carbon chain from chemical attack (Doban, Sperati, and Sandt). From the theory of solubility, it is expected that the miscibility of hydrocarbons and fluorocarbons will be low. Experimental measurements indicate that the miscibility is even less than was expected from the theory. The possible explanations for this have been discussed by Scott. 

Another possible way of overcoming the limitations posed by the presence of water in the suspension polymerisation process is to substitute the continuous water phase with alternative solvents that could still act as dispersing medium for the monomer mixture but better preserve noncovalent interactions in the template-monomer assembly. For example, liquid fluorocarbons are chemically inert and do not affect interactions which are used in noncovalent imprinting. Use of such solvents for the preparation of MIP microbeads has been demonstrated already in 1996 by Mayes and Mosbach [16,17]. A range of MIPs were prepared using Boc-l-phenylalanin as the template, MAA as the functional monomer and different kinds and amounts of crosslinkers and porogenic solvents. The resulting MIP microbeads... 

Teflon, a fluorocarbon polymer, is well known for chemical inertness, thermal stability at temperatures up to 290°C, and excellent electrical insulating properties. Most inorganic and many organic compounds are insoluble in it. Teflon also exhibits a relatively large hydrogen gas permeability. It, therefore, has potential as a selective osmotic membrane for hydrogen. 

Fluorocarbons are compounds of carbon, fluorine, and chlorine with little or no hydrogen. Fluorocarbons containing two or more fluorine atoms on a carbon atom are characterized by extreme chemical inertness and stability. Their volatility and density are greater than those of the corresponding hydrocarbons. However, environmental regulations have restricted the use of many of these compounds. 

Perfluoroelastomers represent a special subgroup of fluorocarbon elastomers. They are essentially rubbery derivatives of PTFE and exhibit exceptional properties, such as unequaled chemical inertness and thermal stability. Currently, there are two types of known commercial perfluoroelastomers, KALREZ and PERLAST . These have ASTM designation FFKM. 

The original basic fluorocarbon, and perhaps the most widely known one, is tetrafluo-roethylene (TFE). It has the optimum electrical and thermal properties and almost complete moisture resistance and chemical inertness. However, TFE does cold-flow or creep at moderate loading and temperatures. Filled modifications of TFE resins are available these are generally stronger than unfilled resins. Fluorinated ethylenepropylene (FEP) is similar to TFE except that its operating temperature is limited to 200°C. FEP is more easily processed,... 

Bromotrifluoroethylene (BFE)or Trifluoro-monobromoethylene, BrFC CFa mw 160.94. The name is used both for the monomer and polymers made from it. The polymers are usually clear oils at RT and non cracking solids at -65°F(—54°C). The typical fluorocarbons are chemically inert, thermally stable, and nonflammable. The monomer can be prepd similarly to CFE from tribromotrifluoroethane and zinc. BFE polymers are used as flotation fluids for gyros and accelerometers used in inertial guidance systems. Can also be used as CFE (chlorotrifluoroethylene) polymers, but are more expensive Refs 1) Beil 1, 189 2) CondChemDict... 

Caution. Lead is an electrically conductive material. The designer should be careful not to place carbon brick and/or carbon-filled mortar in contact with or very close to lead linings where the service includes an electrolyte in solution, as lead and carbon will form a galvanic couple, with the carbon as anode and the lead cathodic. This will result in the wasting of the lead. If carbon brick or carbon-filled mortars are to be employed in the same design, an electrical insulating barrier should be placed between them and the lead. Such barriers may be Teflon or other fluorocarbon sheet, a thick layer of a carbon-free, chemically inert mortar, or a thick layer of ceramic or organic fiber. 

Properties Fluorocarbons are chemically inert, nonflammable, and stable to heat up to 260-315C. They are denser and more volatile than the corresponding hydrocarbons and have low refractive indices, low dielectric constants, low solubilities, low surface tensions, and viscosities comparable to hydrocarbons. Some are compressed gases and others are liquids. 

The effects of fluorous solvents and reagents have been utilized since the beginning of the 1990s. The first practical applications were the immobilization and recovery of expensive or toxic catalysts [3] and the use of chemically inert fluorocarbons to stabilize reactive intermediates [4] (Scheme 3.1). 

The main requirements of the separating agent are that it be selective, be readily separable from the components of the mixture to be separated, and be chemically inert to it. For isotopic mixtures in the form of a permanent gas, such as neon or methane, a readily condensible vapor such as steam or mercury has been used. For UF feed neither of these can be used because of chemical reactivity, and fluorocarbon vapor is specified. Selectivity is enhanced by using a separating agent of appreciably higher molecular weight than the components to be separated. 

Perfluorination techniques have been developed for the conversion of many hydrocarbons to their perfluorinated counterparts. Fluorocarbons are chemically inert because of their kinetically unreactive carbon skeletons and have been considered as blood substitutes because of their high oxygen solubility. The thermal stability and low secondary bond forces of fluorocarbons have contributed to their use as greases, lubricants, and vapor-phase heat transfer reagents. 

CHEMICAL PROPERTIES generally stable under ordinary conditions of use and storage calcium fluoride can react with hot concentrated sulfuric acid to liberate hydrogen fluoride fluorocarbons are chemically inert to most materials fluoroamides can react with lithium tetrahydroaluminate and with sodium at very high temperatures some fluorinated cyclopropenyl methyl ethers react with water or methanol FP(NA) LFL/UFL (NA) AT (NA) HC(NA). 

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