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Rice. 155 Belt bearing material
The range of antifriction thermoplastics also includes plastics based on polyimides, polyurethanes, pentaplast, etc.
Typical antifriction thermoplastics are plastics based on phenol-formaldehyde and epoxy resins, ASP plastics and organosilicon polymers.
Phenol-formaldehyde resins (PFR) are obtained by polycondensation of phenol with aldehydes in the presence of catalysts. The materials of this class include antegmite - highly filled with graphite FFS. Its advantages are anti-friction, resistance to media and thermal shocks. Fibrous phenolic plastics are composites containing reinforcing fibers in a FFS matrix. These are durable, chemically resistant anti-friction materials. Faolite is an acid-resistant tribotechnical material based on FFS filled with asbestos, graphite and talc. Textolites are layered plastics with a filler in the form of wavy sheets. The high strength of textolites depends little on temperature, and antifriction is combined with resistance to oils, fuels, weak solutions of acids and alkalis.
Epoxy resins are named after the epoxy groups in the resin molecule. They are cured with special substances - hardeners, creating a spatial network of covalent bonds. They have good adhesion to metals, high strength and chemical resistance. To obtain antifriction materials, epoxy resins are filled with graphite and molybdenum disulfide. Very popular 20-25 years ago, these materials have now lost their significance.
In aviation, nuclear power and vacuum technology, ASP plastics are used - anti-friction self-lubricating plastics. Their typical representative is AMAN, an antifriction material of the Academy of Sciences. It is a multi-component thermosetting plastic with high thermal and radiation resistance. AMAN and similar ones TESAN, VILAN, ESTERAN are expensive, and therefore they are used in special cases: in high vacuum, at temperatures of about 600K, etc.
Organosilicon polymers are high-molecular compounds containing silicon and carbon atoms as part of the elementary unit of the macromolecule. They are characterized by high heat resistance (up to 600K), antifriction and wear resistance. Silicone rubbers are the starting product for obtaining frost- and heat-resistant rubbers.
Carbon materials - a set of composite materials for tribotechnical purposes containing carbon-based components. It includes carbon plastics and composites on carbon and graphitized matrices.
Carbon plastics are polymeric materials containing carbon fibers in the form of bundles, mats, chopped fibers as a reinforcing component. Their use as antifriction materials is due to the presence of graphite, which is a solid lubricant and has a high thermal conductivity. Carbon plastics combine high strength and low density.
Composites on a carbon and graphitized matrix are produced by pressing coke, soot or graphite on a binder of pitch - the remnants of the distillation of tar and resins. Then the workpiece is fired, turning the bond into a carbon matrix. The graphitized matrix is formed from the carbon matrix after additional heat treatment at 1300K. Both types of matrices have pores that can serve as a reservoir for oils. The tribotechnical characteristics of the material of this class, hymanite, are practically constant over a wide range of temperatures, including cryogenic ones.
Ceramic-metal antifriction materials contain solid lubricant components. They can operate without lubrication when the friction zone is contaminated with solid particles. The following groups of such materials are used in technology.
Porous alloys of iron and graphite (iron graphite), bronze and graphite (bronze graphite), aluminum and graphite (aluminum graphite), as well as silver and copper with graphite are used in plain bearings and sliding electrical contacts. They are characterized by high electrical and thermal conductivity. Instead of graphite, disulfides and diselenides of metals, boron nitride, etc. are used.
Tape metal-ceramic materials contain as a base a metal tape, on which a porous layer of ceramic powder is baked. This layer is then impregnated with a metal alloy such as babbitt.
This group also includes coatings from inorganic solid lubricants synthesized on the friction surfaces of metal parts. For example, a film of molybdenum disulfide is applied to a titanium part, heated in vacuum to 900K, and then blown with sulfur vapor. As a result, a lubricating coating with a thickness of about 50 µm is formed on the part. Thus, the operability of bearings of solar batteries and rotary devices of space vehicles is ensured.