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Alkyl methacrylate and styrene terpolymers as lubricating oil viscosity index improvers

The properties of styrene / dodecyl methacrylate / octadecyl methacrylate terpolymers as viscosity index improvers of lubricating mineral oils were investigated. Terpolymers of different composition and molar mass were prepared by peroxide initiated polymerization of the monomer mixture in a mineral base oil solution. All the terpolymer solutions in base oil exhibited high kinematic viscosity and viscosity index values (> 130) proving high thickening efficiency. The ratio of viscosity values at 100 oC and 40 oC of styrene / alkyl methacrylate additive solutions was between 0.95 and 1.0 showing the coherent thickening effect in a wide temperature range, comparable with pure alkyl methacrylate additives. Increasing content of styrene in the additive and decreasing molar mass of terpolymer resulted in a decrease of viscosity and viscosity index while the shear stability increased. The obtained results give the guidelines for optimization of terpolymers' composition and structure in order to assure the best lubricant application properties.

styrene ; alkyl methacrylate ; terpolymer ; mineral oil ; viscosity index ; shear stability

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