Viscosities of Liquid Fluorocompounds

In spite of their interest, viscosities of fluorocarbon compounds are scarce, and the available data are unreliable and of poor accuracy. In this work, viscosity measurements of linear, cyclic, aromatic, and R-substituted perfluorocarbons were carried out in the temperature range between (298.15 and 318.15) K using an Ubbelohde viscometer. The experimental results show that fluorinated compounds present viscosities considerably higher than their hydrocarbon homologues as expected. The viscosities increase from linear to aromatic to cyclic perfluorocarbons and within each family with the molecule size. The R-fluorine substitution by bromine increases the fluorocarbon viscosity due to the molecular weight increase. The Sastri-Rao method, a group contribution method for the liquid viscosity prediction, was applied for all the fluorocarbons where the viscosity was experimentally measured in this work. Using the new experimental data from this work, new group contribution values are proposed for fluorocarbon compounds allowing for a reduction of the average relative deviation from 12.0 % to 1.3 %.