Asbestos gasket materials
Asbestos is a fibrous mineral that can split into thin and flexible fibers. Asbestos is characterized by high heat resistance, electrical and thermal insulation properties, it does not burn. Its density (if asbestos in the form of a piece) is 2000 - 2500 kg/m3. Withstands an increase in temperature to 300 ° C, and at 386 ° C the material has lost its properties, because it goes adsorption water. At temperatures above 400 ° C begins an irreversible process - goes water has a composition of the material itself, ie, it breaks down, quickly loses strength and easily crumbles into powder. The melting point of asbestos is 1500°C.
Because of its high heat resistance, asbestos is widely used as a gasket material in nodes with high temperature (e.g., elements of friction joints, gaskets on mufflers, etc.). Asbestos can also be used as gaskets for cylinder heads, but only in a metal shell (foil) to avoid direct contact with hot gases.
Asbestos board is made on the basis of chrysotile asbestos. There is a general purpose asbestos board (brand CAON-1 and CAON-2), and there is just a laying - KAP (asbestos cardboard laying). Asbestos cardboard is often used in the form of a soft core when sealing the combined type.
Asbestos sheets are made of several brands: LA-1, LA-1A, LA-2, LA-3A, LA-3B.
Asbestos threads and cords, fabrics, paronite, asbestos tapes are used for various kinds of auxiliary equipment, and in heat insulation works crushed material is also used.
Paronite is a sheet gasket material, which includes approximately 60 -75% asbestos, 12 - 13% of sulfur rubber, and the rest - mineral fillers (talc, clay, feldspar, etc.). According to State Standard 481-80 several grades of paronite are produced: PE, PON and PON-1, PC, PMB and PMB-1. Paronite is bonded with glue 88H. If it is necessary to make a gasket of large dimensions, the edges are butted with an overlap or a "dovetail". Then under pressure at room temperature is maintained for 2 hours.
Felt gasket materials
Made from woolen fibers. It is also a sheet material. The air pores in the felt occupy about 75% of the volume, so it is a very porous material. The density of felts is 200 - 430 kg/m3. Technical felting is divided into: coarse-coarse, half-coarse and fine wool. Felt is characterized by high shock-absorbing properties, sound and heat insulation. Felt is not resistant to heat (destroyed even at 75 ° C). Also not resistant to acids and alkalis, moths and fungi.
Cork gasket materials
This type of gasket material is used in environments where there is little stress. Where moisture and petroleum products may be present (e.g., fuel pump filter cups, rocker arm covers, engine valve covers, etc.). Cork is pressed cork oak bark. Cork can even be used as a box-type packing.
Paper sealing materials
Paper is a fibrous thin sheet material. Wood pulp, cellulose, paper pulp, semi-cellulose, cotton fibers, etc. are used as raw materials for making paper and paperboard. Cardboard is a paper with a mass of 1m2 of more than 250 grams.