ANTIPYRENES (EN: antipyrenes; DE: Antipyrene; FR: antipyrenes; ES: antipirenos; RU: антипирены) are the substances, which protect the wood, woven fabrics, and other materials of organic origin against ignition and independent combustion.
Within the mining craft, antipyrenes are used for the improvement of the fire resistance of the roof support of the underground workings, and so on. The protective action of antipyrenes is determined by the low temperature of their melting point with the formation of the dense film, which prevents the access of oxygen to the material, by the emission of the inert gases or vapours during the heating, which are hindering the ignition of gaseous products of decomposition of the protected material, by the outflow of the large quantity of heat for the melting, evaporation, and dissociation of antipyrenes, which protects the materials, which are impregnated with them, against the heating to the temperature of decomposition, and finally, by the increased charring of materials, which are impregnated with antipyrenes. The most common types of antipyrenes are: phosphates of ammonium (diammonium phosphate, monoammonium phosphate, and their mixture), ammonium sulphate, borax and boric acid, less often ammonium chloride or zinc.
In order to improve the fire resistance of the roof support of the underground mining workings, they use most often the fire-resistant coatings, which are consisting of the aqueous solution of silicates (liquid glass), powdered asbestos, or volcanic dust, which are prepared at the land surface or within the workings proper, with the help of the special installations. The coating of the roof support with this composition is performed with the help of portable apparatuses and mobile installations with productive capacity of 50 and 100 square metres per hour respectively. With the thickness of the layer of 2-2.5 millimetres, there is consumed 2.5-3 kilograms of the fire protective composition for the covering of 1 square metre of the surface of the wooden roof support; the time of hardening is 4-6 hours.
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