Rheological characterization of mixtures containing TBAB + Glycerol

Ionic liquids (ILs) have attracted considerable attention from both industry and academia as alternative solvents. The addition of ILs to fluids affects the behavior of the physical properties of these mixtures. In this work,  are studied, which are formed by the combination of tetrabutylammonium bromide [TBAB] which is quaternary ammonium salts (HBA), and glycerol, which is a type of polyalcohol (HBD), and were prepared at a molar ratio (HBA):(HBD) of 1:2, 1:3, 1:4 and 1:5. The viscosities of these mixtures were determined as a function of shear rate the temperature range of 293.15 – 323.15 K. All mixtures were subjected to shear rates of 0.1, 10 and 50 s^-1. For a 1:2 molar ratio mixture, the viscosity behavior with temperature does not follow the Arrhenius model, except at a shear rate of 50 s⁻¹. The 1:3 molar ratio mixture exhibited similar behavior to the 1:2 molar ratio mixture, that is, for lower shear rates it was not possible to satisfactorily fit the Arrhenius model for the same temperature range. While the 1:4 and 1:5 molar ratio mixtures exhibit typical Arrhenius viscosity and temperature relationships at all rates studied. Due to the higher glycerol concentration, they exhibit equivalent Newtonian fluid behavior, despite a small shear thinning effect at shear rates close to 0.1 s⁻¹. It was concluded that with increasing glycerol concentration, there is greater crystal dissociation and consequently a decrease in viscosity. Mixtures with molar ratios of 1:2 and 1:3 show viscosity values ​​lower than that of pure glycerol, while mixtures with molar ratios of 1:4 and 1:5 show values ​​higher than that of pure glycerol. In addition, a decrease in the quantity and size of the crystals was observed as the molar fraction of glycerol increased. It is considered that the solubility of the remaining salt crystals in glycerol has a significant influence on the decrease in viscosity with increasing shear rate, especially at higher temperatures.