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]PF6, and 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide, [BMIM][Tf2N], have been measured between (0 and 80) degrees C and at maximum pressures of 238 MPa ([HMIM]PF6) and 300 MPa ([BMIM][Tf2N]) at 75 degrees 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) degrees C at atmospheric pressure with an overall uncertainty estimated at +/- 0.000 05 g.cm(-3) are also reported.