In
the present study, surface light scattering (SLS) was used for
the simultaneous determination of liquid kinematic viscosity and surface
tension of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and of trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze) under saturation
conditions. A new SLS apparatus was built up and checked with 1,1,1,2-tetrafluoroethane
(R134a), and a good agreement of our data from SLS with literature
could be found. With the new apparatus, R1234yf and R1234ze were investigated
in the temperature ranges between (293 and 365) K and between (295
and 373) K. For determination of the liquid kinematic viscosity the
expanded uncertainties on a confidence level of more than 95 % (k = 2) are estimated to be ± 2 % for reduced temperatures T
r (= T/T
c) < 0.95, and ± 6 % for T
r close to 0.99. For the surface tension, the expanded uncertainties
are less than ± 1.5 % (k = 2) in the whole temperature
range.
Low-viscosity
ionic liquids (ILs) based on the anions [B(CN)4]− (tetracyanoborate) and [C(CN)3]− (tricyanomethanide)
are currently discussed
as alternative working fluids for various applications. The dynamic
viscosity of such ILs carrying [1-alkyl-MIM]+ (1-alkyl-3-methylimidazolium)
cations was investigated via determination of the translational particle
diffusion coefficient by dynamic light scattering (DLS). The long-term
stability of suspensions of different particles in the ILs, their
particle diameters, and the influence of laser power on the measured
particle diffusion coefficient for semitransparent ILs were studied.
For temperatures from 283 to 353 K at atmospheric pressure, the dynamic
viscosity of the four pure ILs forming stable suspensions was obtained
with an uncertainty of less than 5% (k = 2) and agrees
with literature. Absorption of CO2 at pressures up to 0.87
MPa induced a distinct decrease in the dynamic viscosity. Differences
between the viscosities of the different systems can be explained
by varying strength of molecular interactions.
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