TheSE NEW BEARINGS owe their properties and certain advantages over other bearing materials to Polytetrafluorethylene, known as PTFE. PTFE is a long straight chain plastic consisting of carbon and fluorine with an unusually low dry surface coefficient of friction in the region of 0.05. This value is comparable with that between ice and ice and is lower than boundary friction usually associated with a well lubricated bearing. This property is due to the unique surface of this material and does not depend upon the formation of a low shear strength film, as is the case with graphite. Therefore, under ideal conditions, no appreciable wear takes place and any wear that occurs is due to the roughness of the mating surface “ploughing” through the PTFE. This material is stable up to 327°C. which means that it can be used as a bearing material in an ambient temperature of 280°C. since this will give permissible margin for bearing temperature rise. Higher temperatures can be tolerated if cooling is provided. The chemical properties of this plastic are such that it is not attacked or affected in any way by known organic liquids, solvents, acids, gases, etc. except for molten potassium, molten sodium and florine gas.
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