Dielectric fluid

The silicone oils and silicone resins find application as (i) lubricants (their change of viscosity with temperature is small), (ii) hydraulic fluids (they are unusually compressible), (iii) dielectric fluids, (iv) for the pro duction of water-repellant surfaces, and (v) in the electrical industry (because of their high insulating properties). 

Dielectric films Dielectric fluids Dielectric insulators Dielectric masking Dielectric materials Dielectric permittivity Dielectrics... 

Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

Silicone Fluids. Sihcone fluids are used in a wide variety of appHcations, including damping fluids, dielectric fluids, poHshes, cosmetic and personal care additives, textile finishes, hydraiflic fluids, paint additives, and heat-transfer oils. Polydimethylsiloxane oils are manufactured by the equihbrium polymerisation of cycHc or linear dimethyl silicone precursors. Trifunctional organosilane end groups, typically trimethylsilyl (M), are used, and the ratio of end group to chain units (D), ie, M/D, controls the ultimate average molecular weight and viscosity (112). Low viscosity fluids,... 

Other Chlorobenzenes. The market for the higher chlorobenzenes (higher than di) is small in comparison to the combined mono- and dichlorobenzenes. Trichlorobenzenes are used in some pesticides, as a dye carrier, in dielectric fluids, as an organic intermediate and a chemical manufacturing solvent, in lubricants, and as a heat-transfer medium. These are small and decreasing markets. 

This force equation can now be used to find the force in model systems such as that of an ideal dielectric sphere (relative dielectric constant Ko) in an ideal perfectly insulating dielectric fluid (relative dielectric constant K ). The force can now be written as... 

PCBs and PCTs are particularly troublesome liquids because of their toxicity and persistence in the environment. They are defined as polychlorinated biphenyls, polychlorinated terphenyls, monomethyl-dibromo-diphenyl metliane, monomethyl-dichloro-diphenyl metliane or monomethyl-tetrachlorodiphenyl methane. With low electrical conductivity and heat resistance they found wide use as dielectric fluids and were formerly used as hydraulic fluids. PCBs have not been made in the UK since 1977 and whilst most new uses for the substance are banned in most countries, around two-thirds of the 1.5 million tonnes manufactured in Europe and the US prior to 1985 still remain in equipment such as transformers. PCTs have been used in the past in a restricted range of specialist industrial applications. 

These compounds find use as cooling and dielectric fluids, in polishes and waxes as release and antifoam agents, and for paper and textile treatment. 

The five largest uses for PCBs prior to 1970 were dielectric fluids in capacitors, plasticizers, lubricants, transformer fluids, and hydraulic fluids. They were also used widely in protective coatings, sealers, putty, grinding fluids, printing inks, pattern waxes, carbonless paper, etc. (see Chap. 1). Because of this widespread PCB use they are found throughout the environment [363-365]. A number of important properties of PCBs are discussed below along with information on their distribution and persistence in the environment. 

The most common partition coefficient encountered in environmental work (Sect. 2.1.4) is the octanol water partition coefficient (K0VI) and the solid phase carbon-water partition coefficient (Koc). A partition coefficient for dissolved organic matter-water (i. e., Kd ()M) or dissolved organic carbon-water (i. e., Kd oc) occasionally appears in the literature. In the case of PCBs, Boyd and Sun [378] defined a partition coefficient for residual transformer oil and water as Kd oil, while Sun and Boyd [379] defined a coefficient for PCB dielectric fluid-water as Kd pen-These authors [378,379] identified a total partition coefficient that com-... 

Polychlorinated biphenyls (PCBs) were manufactured by catalytic chlorination of biphenyl to produce complex mixtures, each containing 60-90 different PCB molecular species or congeners (see Chaps. 1 and 4). In the United States, PCB mixtures were manufactured by Monsanto under the trade name Aroclor and were widely used as dielectric fluids in capacitors and transformers from 1929 to 1978. PCBs are widespread contaminants of aquatic sediments and continue to be a focus of environmental concern because they tend to accumulate in biota and are potentially toxic. The following sections show the most effective bioremediation techniques applied to various PCB contaminated environments ... 

Source Pentachlorobenzene may enter the environment from leaking dielectric fluids containing this compound. Pentachlorobenzene may be present as an undesirable by-product in the chemical manufacture of hexachlorobenzene, pentachloronitrobenzene, tetrachloroenzenes, tetrachloroeth-ylene, trichloroethylene, and 1,2-dichloroethane (U.S. EPA, 1980). 

Uses Solvent in chemical manufacturing dyes and intermediates dielectric fluid synthetic transformer oils lubricants heat-transfer medium insecticides organic synthesis. 

Uses. As a dye carrier, an herbicide intermediate, a heat transfer medium, a dielectric fluid in transformers and a lubricant... 

Ethyl Cyanide or Propionic Nitrile, C2H5.CN mw 55-08 colorless, toxic liq with ethereal odor sp gr 0.7829 at 20°/20, nD 1.3664, fr p -91.9°, bp 97.2°, flash p 6l°F (open cup) insol in w sol in ale eth. It can be prepd hy heating Ba ethyl-sulfate with KCN, followed by distillation. It is used as solvent, dielectric fluid andas an intermediate... 

PCBs are synthetic chemicals that exist as oils or waxy substances they do not occur naturally. They were once used in many products including hydraulic fluids, pigments, inks, plasticizers, lubricants, and heat transfer fluids, but their primary use was as a dielectric fluid in electrical equipment. Because of their high thermal stability, chemical stability, and electrical insulating properties, PCB fluids were used extensively in transformers, fluorescent light... 

Gevao et al. (2000) recently reported the presence of polychlorinated naphthalenes in a lake sediment core taken in northwest England (see Table below for profile of pentachloronaphthalenes or PCNs). Like PCBs, these compounds were used by the electric industry as dielectric fluids in transformers and capacitors. 

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