Lubrication control

A thin surface layer of soft soHd or adsorbed lubricant controls the coefficient of friction for a stmctural metal backing according to the following relation ... 

Contamination can be defined as any unwanted substance or energy that enters or contacts the oil. Contaminants come in many forms and may be highly destructive to the lubricant, its additives, and machine surfaces. It is often overlooked as a source of failure because its impact is usually slow and imperceptible. While it is impractical to attempt to completely eradicate contamination from in-service lubricants, control of contaminant levels within acceptable limits can be accomplished and is vitally important. 

Modifiers can inclnde dyes, thickeners, gelling agents, fillers and lubricity controllers and the like as agents that influence the properties of the uncured composition. Plasticizers, reinforcing and/or toughening agents, adhesion promoters and thermally polymerizable prepolymers may be added as modifiers of the cured adhesives. 

The deformation component can be determined by the lubricated sliding friction. In the presence of a lubricant, the shearing of the interfacial junctions or contacts can be prevented therefore, the total frictional force essentially equals the deformation component. Under the lubricated conditions, surface energetics and shear strength of the lubricant control the friction instead (see Section ill. C.). 

Machining or application cost control Friction reduction Wear control Lubrication control Durability... 

Uses Surfactant intermediate, engine oil lubricant additive, viscosity and pour-point improver, plasticizer, epoxy, antifreeze lubricant, control for leather goods and corrosion inhibitor sizing agent in the alkaline production of paper Features Good thermal stability melt processable cost effective Properties Cl, amber liq, sp, gr, 0,955 vise, 250 cs b.p. 235 5 mm Hg flash pt. (PM-CC)195C... 

Fuel passing through certain hot zones of an aircraft can attain high temperatures moreover it is used to cool lubricants, hydraulic fluids, or air conditioning. It is therefore necessary to control the thermal stability of jet fuels, more particularly during supersonic flight where friction heat increases temperatures in the fuel tanks. 

It is noteworthy, however, that traces of sulfur can have beneficial effects on the anti-wear resistance of fuel injection pumps. It is thus undesirable to reduce the sulfur content to extremely low values unless additives having lubricating qualities are added. Independently from total sulfur content, the presence of mercaptans that are particularly aggressive towards certain metal or synthetic parts is strictly controlled. The mercaptan content is thereby limited to 0.002% (20 ppm) maximum. The analysis is performed chemically in accordance to the NF M 07-022 or ASTM D 3227 procedures. 

The topic of spreading rates is of importance in the technology of the use of mono-layers for evaporation control (see Section IV-6) it is also important, in the opposite sense, in the lubrication of fine bearings, as in watches, where it is necessary that the small drop of oil remain in place and not be dissipated by spreading. Zisman and coworkers have found that spreading rates can be enhanced or reduced by the presence of small amounts of impurities in particular, strongly adsorbed surfactants can form a film over which the oil will not spread [48]. 

Ultra-high vacuum (UHV) surface science methods allow preparation and characterization of perfectly clean, well ordered surfaces of single crystalline materials. By preparing pairs of such surfaces it is possible to fonn interfaces under highly controlled conditions. Furthennore, thin films of adsorbed species can be produced and characterized using a wide variety of methods. Surface science methods have been coupled with UHV measurements of macroscopic friction forces. Such measurements have demonstrated that adsorbate film thicknesses of a few monolayers are sufficient to lubricate metal surfaces [12, 181. 

Aerosol products are hermetically sealed, ensuring that the contents caimot leak, spill, or be contaminated. The packages can be considered to be tamper-proof. They deUver the product in an efficient manner generating Httie waste, often to sites of difficult access. By control of particle size, spray pattern, and volume deUvered per second, the product can be appHed directiy without contact by the user. For example, use of aerosol pesticides can minimize user exposure and aerosol first-aid products can soothe without applying painful pressure to a wound. Spray contact lens solutions can be appHed directiy and aerosol lubricants (qv) can be used on machinery in operation. Some preparations, such as stable foams, can only be packaged as aerosols. 

Unfilled Teflon PFA has been tested in mechanical appHcations using Teflon FEP-100 as a control (24). Tests were mn on molded thmst bearings at 689.5 kPa (100 psi) against AISI 1080, Rc 20,16AA steel, and at ambient conditions in air without lubrication. A limiting PV value of 5000 was found. Wear factors and dynamic coefficients of friction are shown in Table 4. 

Synthetic lubricants are made with neopentyl glycol in the base-stock polyester (24). Excellent thermal stabiHty and viscosity control are imparted to special high performance aviation lubricants by the inclusion of polyester thickening agents made from neopentyl glycol (25,26) (see LUBRICATION AND lubricants). Neopentyl glycol is also used to manufacture polymeric plasticizers that exhibit the improved thermal, hydrolytic, and uv stabiHty necessary for use in some exterior appHcations (27). 

The bulk of hydrauhc fluids is specified and purchased on bid. Specifications and approval fists are issued by some manufacturers of hydraulic pumps and system components that require lubrication as well as power for control signal transmission. U.S. government military specifications for hydraulic fluids are fisted ia Table 12, and ASTM tests that are applicable to hydraulic fluids iaclude the foUowiag ... 

Phosphate ester fluids are the most fire resistant of moderately priced lubricants, are generally excellent lubricants, and are thermally and oxidatively stable up to 135°C (38). Fire-resistant iadustrial hydrauHc fluids represent the largest volume commercial use. AppHcations are made ia air compressors and continue to grow for aircraft use (tributyl and/or an alkyl diaryl ester) and ia hydrauHc control of steam turbiaes ia power generation (ISO 46 esters). 

Nuclear Radiation Effects. Components of a nuclear reactor system that require lubrication include control-rod drives, coolant circulating pumps or compressors, motor-operated valves, and fuel handling devices, and, of course, are exposed to varying amounts of ionising (14). 

The latest government regulations set forth under the Toxic Substances Control Act and in PubHc Health Service pubHcations should be checked before formulating new lubricants. Users of lubricants should request Material Safety Data Sheets for each substance involved plus certification of compliance from vendors. Lubricant compounders should insist on similar information from their suppHers for any additive packages. Manufacturers of both additives and lubricants commonly make toxicity checks on commercial products. 

Lubrication oil additives represent another important market segment for maleic anhydride derivatives. The molecular stmctures of importance are adducts of polyalkenyl succinic anhydrides (see Lubrication and lubricants). These materials act as dispersants and corrosion inhibitors (see Dispersants Corrosion and corrosion control). One particularly important polyalkenyl succinic anhydride molecule in this market is polyisobutylene succinic anhydride (PIBSA) where the polyisobutylene group has a molecular weight of 900 to 1500. Other polyalkenes are also used. Polyalkenyl succinic anhydride is further derivatized with various amines to produce both dispersants and corrosion inhibitors. Another type of dispersant is a polyester produced from a polyalkenyl succinic anhydride and pentaerythritol [115-77-5]. 

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