Voloknit
Voloknit
a molding material consisting of a cellulose (most often fibrous) filler impregnated with a phenol (cresol)-formaldehyde resin. Cotton, sisal, jute, kenaf, and other fibers are used as the filler for voloknit. Other materials used include small pieces of paper or wood veneer, which are sometimes first shredded into fiber; pieces of fabric, producing so-called textolite powder; and cord, producing cord voloknit. In addition to the filler and binding, voloknit contains oleic acid (a lubricant), talc (which raises its fluidity during molding and increases its water resistance), lime, magnesium oxide or hexamethylenetetramine (which accelerate the hardening of the resin), and graphite (which increases the durability of products made from voloknit).
The properties of voloknit are mainly determined by the type of filler. The properties of cotton-pulp-based voloknit are as follows: density, 1.45 g/cm3; Martens yield temperature, 140° C; bending strength, 80 meganewtons per sq m (MN/m2), or 800 kilograms-force per sq cm (kgf/cm2); compressive strength, 120 MN/m2 (1,200 kgf/cm2); modulus of extension, 8,500 MN/m2 (85,000 kgf/cm2); resilience, 9 kilojoules per sq cm (kJ/m2), or 9 kgf-cm/cm2; Brinell hardness, 250 MN/m2 (25 kgf/mm2); water absorption in 24 hours, 9 g/m3; specific surface electrical resistance, 1010 ohms; specific volumetric electrical resistance, 10 megohms-m (109 ohms •cm); electric strength, 4 mega volts per m, or 4 kilovolts per mm. A distinguishing feature of products made of voloknit is their high resilience; in addition, they are resistant to water, mineral oil, gasoline, and weak acids and solvents. They are destroyed by solutions of alkalies, strong acids, or chlorine.
In producing voloknit, the individual components are mixed, and then the raw voloknit is dried. At a temperature of 160°-170° C products of simple (at a pressure of 25 MN/m2, or 250 kgf/cm2) or complex (at a pressure of 40-50 MN/m2, or 400-500 kgf/cm2) shape are molded from the dried, pre-formed voloknit.
Voloknit parts are used in instrument-making and machine building (in cases, housings and covers, gears, flywheels, and bushings) and in construction (door handles, panels, and fittings). Flooring for the steps of subway escalators is also made from voloknit. Parts with good mechanical and antifriction properties (gaskets, rollers, gears, bearings, and bushings) are manufactured from textolite powder.