Viscometric Behaviour of Viscosity‐Index Improvers in Lubricant Base Oil over a Wide Temperature Range: II. Polyalphaolefin Synthetic Base Oil

A polyalphaolefin (PAO) synthetic base oil was used to solvate four polymers known to be viscosity‐index improvers in lubricants, these being an olefin copolymer (OCP), a dispersant olefin copolymer (DOCP), a polymethacrylate (PMA), and a hydrogenated diene polymer (HDP). The kinematic viscosity and density data for each polymer were measured at five concentrations (0.1, 0.2, 0.3, 0.5, and 0.7% by mass) by capillary viscometry over the temperature range −20 to 150°C. The data were analysed using the Huggins equation. When compared to an earlier study using a hydroprocessed (Group II) base oil, the thickening efficiencies of the polymers were generally lower in PAO, which was mainly attributed to the weaker intermolecular hydrodynamic interactions.