Density and temperature dependence of self-diffusion and shear viscosity of perfluorocyclobutane in the dense fluid region

Abstract

The self-diffusion coefficients of liquid perfluorocyclobutane have been measured as a function of temperature and pressure over the density range 1.8⩽ρ/ρc⩽2.9 and the temperature range 0.8⩽T/Tc⩽2.3. The NMR spin-echo technique was employed for the measurement of the diffusion coefficients using a steady magnetic field gradient. Shear viscosities and densities of perfluorocyclobutane have also been determined under the same experimental conditions. Both the diffusion coefficients and shear viscosities are interpreted in terms of the rough hard sphere model of liquids based on the modified Enskog theory. The effective hard core diameter and its temperature dependence are calculated. The Stokes–Einstein relationship with the slipping boundary condition was found to be valid for the liquid studied.