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Low temperature behaviour of metachylate based pour point depressants

Base oils are widely used in different types of engines in order to lower the friction between the moving parts. Usually their basic properties like viscosity, pour point, anti-corrosion are improved by the addition of different additives. One type of such additives is methacrylate based pour point additive. They are easily manufactured by the free radical copolymerization of corresponding methacrylate monomers in solution of lubricating base oil. Therefore, they can be chemically modified relatively simply by the addition of different functional methacrylate comonomers due to similar copolymerization reactivity. This is their noteworthy advantage over competing additives. In this work polymer additives with different composition (methyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, N, N-dimethylaminoethyl, styrene) and molar mass were synthetized. Influence of the composition and molar mass on pour point properties was studied in different base oils by ISO 3016 method and differential scanning calorimetry. Results indicate unambiguous correlation between composition of polymers and crystallization maximum/ enthalpy obtained by DSC. DSC crystallization maxima of polymers has a same trend as pour point results obtained for 0.5 wt% solutions of polymers in base oil. At lower concentration of additives (0.1, 0.5 wt%) there is a noticeable change in DSC curve but in most cases there is a low or no correlation between composition and crystallization maximum/enthalpy. This indicates that beside composition intra- and intermolecular interactions in polymer solution and their influence on the solution viscosity, solubility of the polymer, hydrodynamic volume of the polymer coil have a noticeable effect on overall crystallization behaviour. Obtained polymer additives have a positive effect when added in lubricating oils which results in lowering the pour point up to 30 °C. Thermal stability was assessed by thermogravimetric analysis and has shown that in case of methacrylate terpolymers, decrease in molecular weight of polymer increases the thermal stability, while in the case of styrenemethacrylate terpolymers, decrease in the polymer molecular mass has almost no effect.

pour point, lubricating oil, methacrylate, DSC

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