Effect of pressure on the transport properties of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide and 1-hexyl-3-methylimidazolium tetrafluoroborate

•High-pressure self-diffusion coefficients are presented, [HMIM]BF4 and the IUPAC reference material [HMIM][Tf2N.•High-pressure conductivities are presented for [HMIM][Tf2N].•Slopes for the SES and Walden plots are consistent for self-diffusion coefficients and molar conductivities.•Velocity cross-correlation and resistance coefficients calculated for [HMIM][Tf2N] with no evidence for ion association.•Density scaling is applied: the scaling coefficients are consistent with the theoretical work of Knudsen et al.