Analysis of Mobility, Volatility, Morphology, Physical States, and Oxidation Stability of Selected Contact Lubricants

The increasingly strenuous and variable thermal environments in which static gold-plated contacts must operate has generated a need for expanded information on the physical properties of traditional and new lubricant materials. This work investigated the mobilities, volatilities, oxidation stabilities, morphologies, and physical states of microcrystalline waxes, synthesized hydrocarbons, polyphenyl ether, di-2-ethylhexylsebacate, and polyethylene glycol over a wide temperature range. The mobilities of the microcrystalline waxes, high viscosity synthesized hydrocarbons, polyphenyl ether, and polyethylene glycol were all very low. The relative volatilities were: di-2-ethylhexylsebacate > low viscosity synthesized hydrocarbon > polyethylene glycol > polyphenyl ether > microcrystalline wax> high viscosity synthesized hydrocarbon. Oxidation tests indicated that the microcrystalline waxes and synthesized hydrocarbons were mildly sensitive to oxidation. Morphologies of thin films, determined up to 150°C with scanning electron microscope, were variable. The microcrystalline waxes and high viscosity synthesized hydrocarbons existed as generally uniform films with some clustering. The di-2-ethylhexylsebacate produced a very uniform film, and the polyphenyl ether distributed itself in a beaded nonwetting manner.