Bearings, polytetrafluoroethylene

Plastics. Almost all commercial plastics find some use both dry and lubricated for sliding at low speeds and light loads the most commonly used thermoplastics are nylon, acetal resins, and polytetrafluoroethylene (PTFE). Typical thermosetting resins for bearing appHcations are phenoHcs, polyesters, and polyimides. Table 8 compares the characteristics of plastic bearing materials with those of graphite, wood, and mbber which find use in somewhat similar appHcations. 

With plain bearing surfaces of steel, a great improvement can be obtained by phosphating and impregnating the layer with oil. The inherent porosity of the phosphate films provides minute reservoirs for the oil. Should it be necessary to operate a bearing dry, then either a bonded film of MoSj or p.t.f.e. (polytetrafluoroethylene) can be used to advantage. Both materials have excellent frictional and wear characteristics. 

R. F. Chanshev, S. V. Kovtunenko, F. D. Tsikunkov, R. A. Ismakov, G. V. Konesev, and R. A. Mul5mkov. Lubricant for cutter bit bearings— contains ethylene-propylene synthetic rubber, zinc dioctyl-phenyl dithio-phosphate, polytetrafluoroethylene and mineral oil. Patent SU 1778162-A, 1992. 

Polymers used for seat and plug seals and internal static seals include PTFE (polytetrafluoroethylene) and other fluorocarbons, polyethylene, nylon, polyether-ether-ketone, and acetal. Fluorocarbons are often carbon or glass-filled to improve mechanical properties and heat resistance. Temperature and chemical compatibility with the process fluid are the key selection criteria. Polymer-lined bearings and guides are used to decrease friction, which lessens dead band and reduces actuator force requirements. See Sec. 28, Materials of Construction, for properties. 

There are some special cases for which it is unnecessary to add a lubricant. Magnetic bearings and bearings that are suspended by a pressurized gas have no metal-to-metal contact so that wear and heat buildup are avoided. Several companies sell oil-free vacuum pumps that eliminate the trouble and expense of changing the oil, disposal costs, and contamination of process chambers, which is especially important in the manufacture of semiconductors and liquid crystal crystal displays.40 Plastic gears of nylon or polytetrafluoroethylene are self-lubricating and need no added lubricant. They reduce the noise associated with ma-... 

Polyblends of polyamides with polyethylene and of polyacetal with polytetrafluoroethylene have found application as bearing materials. 

Ryton Polyphenylene Sulfide is a new commercial plastic which is characterized by good thermal stability, retention of mechanical properties at elevated temperatures, excellent chemical resistance, a high level of mechanical properties, and an affinity for a variety of fillers. It is produced from sodium sulfide and dichlorobenzene. Its unusual combination of properties suggests applications in a variety of molded parts such as non-lubricated bearings, seals, pistons, impellers, pump vanes, and electronic components. Tough coatings of polyphenylene sulfide can be applied to metals or ceramics by a variety of techniques and are used as protective, corrosion-resistant coatings in the chemical and petroleum industries. Incorporation of small amounts of polytetrafluoroethylene provides excellent non-stick properties in both cookware and industrial applications. 

CF2=Cp2 (tetrafluoroethene) (CF CF2) Polytetrafluoroethylene, PTFE, Teflon Nonstick coating, electrical insulation, bearings... 

Blends of polytetrafluoroethylene (PTFE) are replacing metals in applications such as gaskets, bearings, and piston rings in automotive engines. The Polycomp R range of LNP Corporation includes... 

The coating that is placed on cookware is usually polytetrafluoroethylene (PTFE), marketed as Teflon by DuPont . The strength of the C-F bond, and its reluctance to interact with just about anything else, makes Teflon very heat-resistant and slippery stuff. Aside from coating cookware, it s used to make gears and bearings, and it s a key component of Gore-Tex (the material your waterproof jacket is made of). 

Any gas or vapour produced by burning is carefully smelled and recorded, bearing in mind that it may be toxic (polytetrafluoroethylene) or corrosive (cellulose acetate). The pH of any vapour generated is determined by holding Universal Indicator paper or pH indicator strips moistened with distilled water in its path. Plastics producing acidic vapours include cellulose nitrate and acetate, polyester, polyurethane, PVC. Those forming neutral vapours are polyethylene, polystyrene, acrylics, polycarbonate, silicones and epoxies. Alkaline products originate mainly from nylon and formaldehyde plastics. 

MAJOR APPLICATIONS Nylon 4,6 is often blended with glass fiber or polytetrafluoroethylene md is used in underhood automotive parts, gears, electrical parts, and bearings. 

Polymers and polymer matrix composites are increasingly replacing metals in bearings, cams, gears, and other sliding components. Polytetrafluoroethylene (PTFE) is an example of a self-lubricating polymer that is widely used for its wear resistance. Fiber reinforcement of PTFE improves other mechanical properties without sacrificing the wear performance. 

Charnley develops the technique of low friction arthroplasty (LFA). Usirig polytetrafluoroethylene (PTFE) as the bearing material (Charnley 1961) implants were fabricated either by Charnley in his home workshop or in the machine shop at Wrightington and chemically sterilized. 

Polytetrafluoroethylene Coating of cooking pans, lubricant-free bearings, etc. 

Lubricity and Abrasion Resistance. In plastic gears and bearings, these qualities are improved by adding solid powders such as brass, molybdenum sulfide, graphite, polyethylene, and especially polytetrafluoroethylene. 

Polytetrafluoroethylene is a material that s hard, heat resistant, and extremely slick. This material is used as bearings, valve seats, and (most importantly to me) nonstick coating for pots and pans. 

An important example of a polymer is that of polyvinylchloride, shown in Figure 9.15. This polymer is synthesized in large quantities for the manufacture of water and sewer pipe, water-repellant liners, and other plastic materials. Other major polymers include polyethylene (plastic bags and milk cartons), polypropylene (impact-resistant plastics and indoor-outdoor carpeting), polyacrylonitrile (Orion and carpets), polystyrene (foam insulation), and polytetrafluoroethylene (Teflon coatings and bearings) the monomers from which these substances are made are shown in Figure 9.16. 

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