Temperature and Pressure Dependence of the Viscosity of the Ionic Liquids 1-Hexyl-3-methylimidazolium Hexafluorophosphate and 1-Butyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide

The viscosities of the ionic liquids 1-methyl-3-hexylimidazolium hexafluorophosphate, [HMIM]PF 6, and 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide, [BMIM][Tf 2 N], have been measured between (0 and 80) °C and at maximum pressures of 238 MPa ([HMIM]PF 6 ) and 300 MPa ([BMIM][Tf 2 N]) at 75 °C with a falling-body viscometer. The overall uncertainty is estimated at ± 2 %. Modified Litovitz and Vogel−Fulcher−Tammann (VFT) equations are used to represent the temperature and pressure dependence. The Angell equation relating the strength factor D, the VFT parameter T 0, and the glass temperature T g is confirmed. Densities between (0 and 90) °C at atmospheric pressure with an overall uncertainty estimated at ± 0.000 05 g·cm -3 are also reported.