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

Low-temperature properties need improvement before vegetable oils can recei ve wider recognition as biodegradable lubricants. Effects of dilution with major biodegradable fluids, namely poly alpha olefin (PAO 2), disodecyl adi pate (DIDA), and oleates, as well as impact of pour point depressant (PPD), were investigated. Since solidification of mixed unsaturated triacylglycer ols is a complex thermodynamic process, the study was limited to pour point determinations. Vegetable oils demonstrated higher pour points with increa sed saturation and molecular weight. Cis unsaturation and hydroxy groups fa vored lower pour points. Dilution with oleates appeared less effective than dilution with PAO 2 and DIDA. Addition of 1% PPD (w/w) depressed pour poin ts down to -33 degrees C for canola and -24 degrees C for high-oleic sunflo wer ails. However, neither higher amounts of PPD nor incorporation of dilue nt produced further depression. Depression of pour points was not proportio nal to the amount of diluent and ceased with further dilution. Low-temperat ure performance of vegetable oils limits their prospect as biodegradable lu bricants, but well-balanced usage of PPD and diluents can deliver some impr ovements.