Asbestos Plastics

Asbestos Plastics

 

plastics with fillers of fibrous asbestos materials. Asbestos plastics are divided into laminated plastics, or asbestos textolites (asbestos-fabric filler); laminated insulation (paper) and asbolite (cardboard); asbestos-fiber plastics (compositions based on fibrous asbestos saturated with synthetic resins); and asbestos plastics based on asbestos fibers, mats, or cloth previously created in the articles. In the production of asbestos plastics, phenol-and melamine-formaldehyde resins are mainly used as binders; silicon-organic and furan resins (content usually 30–40 percent) are used less frequently.

The process of preparation of sheets or plates from asbestos plastics consists of saturating the filler with resin solutions or emulsions, drying the saturated filler, and then pressing it at high temperatures and pressures (for phenolfor-maldehyde binders, at 150–160°C; and 9–11 meganewtons per sq m [MN/m2; 1 MN/m2 ≈ 10 kg-force/cm2]). Pieces made from asbestos plastic sheets are prepared by pressing or mechanical processing; from asbestos fibers, by compression or flow molding. Pipes from asbestos plastic layers are prepared by winding the saturated filler on a cylindrical holder and then by hardening the binder. Large-size articles of complicated shape can be obtained from mats or canvases (with mainly parallel arrangement of the fibers) which are saturated by resins and then pressed under medium pressures (up to 1.5 MN/m2).

The mechanical properties of asbestos plastics are very stable under the action of moist air and water, as well as under temperatures as high as 500°C. Asbestos plastics not containing organic fillers are stable in tropical weather. The friction coefficient of asbestos plastic materials is 0.25–0.45. The electrical strength of asbestos plastics with silicon-organic binders is approximately 4 megavolts per meter (kilovolts per millimeter); the relative dielectric permeability at 50 Hz is 60–110 picofarads per meter (pF/m), and the absolute dielectric permeability is 530–970 pF/m. Asbestos plastics are widely used in rocket technology for the thermal protection of several rocket parts; blades for rotating pumps, panels for installation of electric switchboards, collectors for small electric machines, and brake shoes for subway trains and airplanes are also manufactured. Large pipelines, fittings, and other items are prepared from asbestos fibers on a phenol-formaldehyde resin base— phaolite.

REFERENCE

Carroll-Porczynski, C. Materialy budushego: Termostoikie i zharoprochnye volokna i voloknistye materialy. Moscow, 1966. (Translated from English.)
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