engleski

Synthesis and properties of dispersive viscosity index improvers

New standards regarding emissions of gases and resulting engine design changes such as implementation of the EGR (exhaust gas recirculation) system in diesel engines led to the changes related to the lubricant requirements and formulations. While the EGR system effectively reduces NOx emissions to the atmosphere, soot load in the lubricant can be expected to increase dramatically, causing the increase of viscosity, fouling, deposits and wear as well as dispersancy failure. This has directed modern lubrication research toward the development of a new type of polymer additives with multiple activities ; in addition to the control of viscosity properties these additives displayed improved dispersancy. Introducing the ability of dispersancy into a polymer additive demands a carefully engineered incorporation of a strongly polar functional group to the main polymer backbone. The most commonly employed functional groups are amines, alcohols, or amides. Such formulated polymer additives will have ability to keep insoluble combustion debris and oil oxidation products dispersed in the oil, which will prevent their deposition on the main part of the engine. This will have a direct effect on minimizing harmful engine exhaust emissions, increasing engine life and controlling oil consumption by maintaining clean engine operation. Polymeric dispersive viscosity index improvers of lubricating oils based on dodecyl methacrylate, octadecyl methacrylate, N, N- dimethylaminoethyl methacrylate and methyl methacrylate (d-PAMA) or styrene (d-PSAMA), were produced by performing copolymerizations isothermally up to the high conversion in mineral base oil solution, using monofunctional or bifunctional peroxide initiator. The obtained kinetics results reveal the benefits of the usage of a bifunctional peroxide initiator over a monofunctional, because complete conversion of monomers was accomplished in the shorter reaction time, performing the process in a full batchwise mode. Investigated application properties demonstrated that d-PAMA and d-PSAMA additives were fully comparable with conventional methacrylate additives, where they also provided other advantages such as higher viscosity index and kinematic viscosity, lower values of pour point temperatures, as well as better dispersant and detergent properties. Thus, by increasing the N, N-dimethyl aminoethyl methacrylate share in copolymers from 2 to 10 mol %, their weight average molecular weight decreased, while kinematic viscosity values at 100 °C remain high.

N, N-dimethyl aminoethyl methacrylate ; alkyl methacrylate ; styrene ; dispersive copolymers

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