About the performance of some viscosity index improvers in a synthetic oil of ester type

Abstract

PurposeThis paper seeks to investigate the influence of chemical structure of ester basestock (trimethylolpropane pelargonate) on the viscosity characteristics of formulations obtained and the operating mechanism of two widely used viscosity index improvers – poly(butadiene‐styrene) and poly(alkyl methacrylate).Design/methodology/approachOil formulations of trimethylolpropane pelargonate and poly(butadiene‐styrene)/poly(alkyl methacrylate) as viscosity index improvers are prepared. Their kinematic viscosity at different temperatures is measured. Relative, intrinsic and characteristic viscosities are calculated from the experimental data.FindingsThe thickening ability of linear polymers from butadiene‐styrene and alkyl methacrylate in a synthetic oil of ester type (trimethylolpropane pelargonate) is clarified. The conformation of these polymers is studied. Results of comparative tests about the influence of the type of polymer and solvent on characteristic and intrinsic viscosity are presented. It has been established that with the increasing of temperature the quality of used synthetic oil decreased and the characteristic viscosity decreased for both polymers. At lower temperatures the intermolecular interaction between the polymeric macromolecules becomes bigger than their interaction with the molecules of solvent. Molecule associates have been possibly formed at low temperature. These associates increase the viscosity of solutions and this increase is bigger at low temperatures in comparison with high temperatures.Practical implicationsViscosity index improvement of poly(butadiene‐styrene) and poly(alkyl methacrylate) is determined. The information about concentrations and viscosity is of practical interest.Originality/valueThe combination of these synthetic basestock and viscosity index improvers is a new one. The data obtained may have value for the oil production.