Depression of pour points of vegetable oils by blending with diluents used for biodegradable lubricants

Low-temperature properties need improvement before vegetable oils can receive wider recognition as biodegradable lubricants. Effects of dilution with major biodegradable fluids, namely poly alpha olefin (PAO 2), diisodecyl adipate (DIDA), and oleates, as well as impact of pour point depressant (PPD), were investigated. Since solidification of mixed unsaturated triacylglycerols is a complex thermodynamic process, the study was limited to pour point determinations. Vegetable oils demonstrated higher pour points with increased saturation and molecular weight. Cis unsaturation and hydroxy groups favored lower pour points. Dilution with oleates appeared less effective than dilution with PAO 2 and DIDA. Addition of 1% PPD (w/w) depressed pour points down to −33°C for canola and −24°C for high-oleic sunflower oils. However, neither higher amounts of PPD nor incorporation of diluent produced further depression. Depression of pour points was not proportional to the amount of diluent and ceased with further dilution. Low-temperature performance of vegetable oils limits their prospect as biodegradable lubricants, but well-balanced usage of PPD and diluents can deliver some improvements.

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