Viscometric Characteristics of Viscosity Index Improvers - Structural Changes in PAO Solutions at Low Temperature 2001-01-1994
The evaluation of the effect of a Viscosity Index Improver (VII) in a mineral oil formulation at low temperatures becomes difficult when wax crystallization occurs, which modifies the oil viscosity-temperature behavior.
In this work, we studied the isolated influence of VII's in rheological characteristics of lubricants, using polyalphaolefin (PAO-4) as a wax free base oil. Brookfield viscosity results of the pure PAO-4 were compared to those of the VII solutions, in four concentrations, from -10°C to -40°C.
The VII thickening power was determined for two commercial polymers from their reduced and intrinsic viscosities in PAO-4 solutions. These parameters were then used to analyze the low temperature behavior of formulated ATF's with two kinds of base oils, one Group II and one Group III. The studied VII's are available in Brazil for the formulation of ATF fluids.