Asbestos

ASBESTOS (from the Greek asbestos-inextinguishable), a group name for several minerals (of the serpentine and hornblende families) united by a technical function—the ability to split into more or less long, thin, durable, and flexible-elastic fibers—and possessing high dehydration and melting temperatures, acid resistance, and good thermal and electrical insulating properties. Asbestos fibers can be subjected to spinning, rope-making, and weaving industrial processes; as a result of such processing, threads, cords, ropes, cables, and fabrics possessing fire- and acid resistance are obtained. However, the largest share of mined asbestos goes to the production of felt-like asbestos materials, obtained either from pure asbestos or from asbestos mixed with various plant or animal fibers, as well as to the production of asbestos pressed masses, obtained by mixing more or less crushed asbestos fibers with binding agents. In the production of electrical insulating asbestos compositions, various resins, bitumens, etc., are used for this purpose; in the production of construction compositions, mineral cements are used. Among construction asbestos materials, asbestos-cement slate on Portland cement (eternite, terrophaserite, denghait, zenith, ternolite, vek, poilite, asbestilite, etc.) has come to the fore recently. It is distinguished by low specific gravity, thermal conductivity, electrical conductivity, water absorption, and cost, along with high elasticity and viscosity, resistance to atmospheric influences, as well as mechanical strength, absence of brittleness, and complete water impermeability. The ability to give these materials any shape and to obtain pipes of any diameter without a seam from them, possessing a number of excellent properties, has made asbestos-cement a material of exceptional importance in general and factory construction, as well as in urban improvement (gas, water, and steam pipelines, sewage, etc.). Among other compositions based on asbestos, one can mention asbestos-coated wood and stones, cements, plasters, water-resistant cement, mineralite, roofing and stove cement, ceramic compositions, paints, for example, 'asbestin', which possesses fire- and moisture-resistance and acid resistance, thermal insulating materials, sound insulating and electrical insulating materials in the form of felts, paper, bricks, stampable masses, coatings, etc. Asbestos materials have enormous sanitary significance; burn-protective and non-flammable fabrics, thermal, sound, and moisture insulators, etc., are manufactured from them. Factory processing of asbestos to obtain various products from it, due to the spread of harmful needle-like dust, requires particularly serious sanitary occupational safety measures. In laboratories, pure fibrous asbestos is frequently used as a filtering material (see Asbestos clothing).