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High Temperature Lubricants
The typical maximum temperature of a high temperature lubricant for continuous use is around 450-650ºF, depending on the chemical composition. However, this encompasses the lower temperature liquid lubricants, while semi-solid and solid lubricants can reach more extreme temperatures of 800-1500ºF. This differs vastly from general purpose lubricants, which start to decompose around 230-250ºF. Often categorized as synthetic lubricants rather than petroleum-based organic lubricants, high temperature lubricants are utilized in industries such as manufacturing, automotive, aerospace, textile, chemical processing, electronics and construction. As a result of the various chemical compositions, high temperature lubricants are able to lubricate a wide variety of parts and materials such as gears, conveyor chains, baking ovens, glass, extrusion equipment, fasteners and bearings. In a sold state, high temperature dry lubricants are commonly made from graphite and molybdenum disulfide (MoS2) because they offer high lubricity and thermal stability.
High temperature lubricants can come in three different states: liquid oils, semi-solid grease and solid dry lubricants. In the liquid state, high temperature lubricants are most often composed of esters combined with hydrocarbons and antioxidant additives or additional stabilizers. Esters are particularly useful for high temperature applications due to their excellent heat-resistant properties. However, the addition of antioxidants is required in order to enhance the thermal stability of the lubricant, although the same reaction does not apply to other liquid base stocks. In a semi-solid state, high temperature grease consists of a base oil, a thickener and additives. While base oils can differ, three of the more common are esters, polyalphaolefins (PAO) and silicone. For the thickener, soap and clay are the most common additives to form lubricating grease. However, they are unable to withstand extremely high temperatures. As a result, materials such as fluoropolymers and fumed silica are used instead since they are proven to have high temperature capabilities. As for the additives, it depends on the requirement of the application. While antioxidant additives are often required, additional additives providing benefits such as enhanced corrosion or wear resistance may also be used.
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