The Pressure-Viscosity Coefficient of a Perfluorinated Polyether Over a Wide Temperature Range

An unbranched perfluoropolyether is the current ball bearing lubricant for deep space flight. We report measurements of viscosity to moderate pressures for the calculation of pressure-viscosity coefficients to temperatures as low as −40°C. A free volume model predicts that a minimum pressure-viscosity coefficient exists at higher temperature. The existence of a minimum αoT is confirmed by viscometry at temperatures to 180°C.