Bituminous Plastics

plastics whose composition includes bituminous materials and fillers. The bituminous materials may be natural or artificial petroleum bitumens or coal tar pitches or their melts; the fillers may be cotton combings (the wastes of textile production) or kieselguhr (the silicon remains of mollusk shells), in amounts of 25–60 percent. Bituminous plastics are made by combining the ingredients at a temperature of 150°-160°C and then cold-rolling the mass obtained into sheet billets 10–15 mm thick. Articles are formed by molding the billets, which have been preheated to 175°C, under a pressure of 12.5–30 meganewtons per sq m (MN/m²) or 125–300 kilograms-force per sq cm (kgf/cm²).

In addition to ordinary bituminous plastics, so-called asbestos-pitch (Russian asbopekolit) plastics based on asbestos, pitch, and kieselguhr are produced. To obtain them a mixture of aqueous suspensions of the components is fed into a paper machine, forming a sheet 1–2 mm thick (asbestos cardboard) or 0.5 mm thick (asbestos paper). Asbestos cardboard is processed into sheet products on platen presses at a temperature of 120°-130°C and a pressure of 15–20 MN/m² (150–200 kgf/cm²). Asbestos paper is used for coiled products (tubes).

Bituminous plastics are thermoplastic materials. They do not change in mass, hardness, or tensile strength after a year of exposure to atmospheric conditions or distilled water, or after heating to 65° C for a period of 160 hours. By varying their composition, bituminous plastics of a wide range of qualities may be obtained: densities of 1,300–2,200 kg/m³, water absorption of 0.07–1.0 percent per 24 hours, Brinell hardness of 0.6–2.2 MN/m² (6–22 kgf/cm²), and electric strength of 6–12 kW/mm.

The main uses of bituminous plastics are in the production of automotive battery housings, roofing materials, and various electrical and radio components.