Askarele

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General structural formula of the polychlorinated biphenyls
1,2-dichlorobenzene , a polychlorinated benzene

Askarele (English askarels ) are mixtures of polychlorinated biphenyls (PCB) or mixtures of PCBs with polychlorinated benzenes , which were used as electrical insulating liquids . Due to their environmental pollution, they are no longer used today.

Manufacture and properties

Polychlorinated biphenyls are prepared by biphenyl batchwise long as chlorinated is, until the desired chlorine content in the end product reached. The askarels made from it are chemically very resistant. They are not flammable and are characterized by their high boiling points and low electrical conductivity . Depending on the composition, their appearance varies from slightly colored liquids to yellow or black, waxy masses.

During the thermal decomposition of askarels, pyrolysis products occur ( dibenzodioxins and dibenzofurans ), which are known as ultra poisons because of their particular toxicity .

use

Due to their low electrical conductivity, relatively high dielectric constant and their non-flammability, askarels have been widely used as electrical insulating fluids in capacitors and high-voltage transformers since the 1930s : almost all metal-paper and oil-paper capacitors manufactured between 1930 and 1980 contained askarels as a dielectric . Askarele were u. a. marketed under the trade names Apirolio, Aroclor, Asbestol, Clophen, Chorextol, Chorinol, Diaclor, Dykanol, Elemex, Elaol, Eucarel, Fenclor, Hydrocor, Hyvol, Inerteen, Kaneclor, Montar, NoFlamol, Phenochlor, Pydraul, Pyralene, Pyroclor and Sorol. When assessing the effects of ascareles on human health, the toxicological properties of the polychlorinated biphenyls are used as a benchmark.

Substitutes

Mineral oils , synthetic esters and silicone oils (so-called transformer oils ), which have sufficient chemical stability and electrical insulation properties, are used as substitutes .

Individual evidence

  1. ↑ Technical rules for hazardous substances: electrical insulating fluids contaminated with PCDD or PCDF (PDF; 96 kB).
  2. ↑ Information from the US EPA on Arochlor and other PCB mixtures .
  3. ↑ Basic information from the US EPA on PCBs .
  4. ↑ Information from ANZECC on the identification of capacitors containing PCBs ( Memento of October 3, 2012 in the Internet Archive ).
  5. ↑ a b Information from the University of Toronto on the history and trade names of the Askarele .

Web links