EVAPORATION RATES FOR VARIOUS ORGANIC LIQUID AND SOLID LUBRICANTS IN VACUUM TO 10-8 MILLIMETER OF MERCURY AT 55°TO 1100°F

摘要

The evaporation rates for various organic lubricants were measured in vacuum (l0-6 to 10-8 mm Hg) and at, ambient temperature to 1100°F. These materials included liquids, greases and solidnThe evaporation rate measurements were made with a vacuum bell-jar evaporation system employing an electronic balance to measure, weight "changes "to one-hundredth of a milligram. The specimens' were heated-by a wire-wound furnace, and evaporated material was condensed on a liquid-nitrogen-cooled condenser, plate. The weight change of the specimen was continuously recorded on a strip chart recorder.nSome of the lubricants examined were polyphenyl ethers, polyalkylene glycols, silicones, fluorocarbon polymers, polytetrafluoroethylene, polychlorotrifluoroethylene, and phthalocyanines. Differences in molecular weight were found-to influence markedly the evaporation rates of lubricants. With a polyalkylene, glycol fluid having a molecular weight of 13,500, the evaporation rate was approximately 10-6 g/sq cm/sec at 550° F. This same evaporation rate was achieved with a 660-molecular-weight fluid at a temperature of 55° F. The results obtained with a series of polyalkylene glycol fluids of different composition "hut having equivalent molecular weights (1000) indicated that the evaporation rate of the series over a range of temperatures could be represented by a single curve. The solids polytetrafluoroethylene, polychlorotrifluoroethylene, and fluorocarbon polymers were also found to exhibit evaporation rates with a molecular weight dependence. For one of the polyphenyl ethers, good agreement was found with data in the literature.