Today’s biobased lubes owe their famed biodegradability to their vegetable-oil or animal-fat origins. But many can’t match the cold-weather performance, cost or oxidative stability of petroleum-based formulations.
The estolides are a different story – or such is the indication from tests carried out by Steven Cermak, Terry Isbell and others at the ARS National Center for Agricultural Utilization Research, in Peoria.
There, the team overcame the pitfalls of standard biobased lubes by chemically connecting different unsaturated fatty acids (FAs). These are the building blocks of high-oleic oils, such as sunflowers, canola and lesquerella.
Normally, an edible oil – for example, from soybeans – is modified to produce the desired biobased industrial product, such as grease or hydraulic fluid. The Peoria team used only the FA components, producing branched chains of either saturated or unsaturated oleic estolides whose performance in crankcase trials rivaled that of mineral-oil-based lubes, which are petroleum-derived.
For example, the lowest temperature at which the scientists could pour a conventional soy-based lube before it thickened into a gel was -0.4 degrees Fahrenheit, whereas for two commercial mineral-oil formulations, the pour points were -4 degrees F and -40 degrees F. This compares to -22 degrees F for the unsaturated oleic estolides and -40 degrees F for the saturated ones.
And in a standard oxidative-resistance test, called RBOT for short, the two estolide lubes withstood oxidative breakdown for 200 and 400 minutes, respectively, versus 60 to 80 for standard biobased formulations, and 200 for mineral oil used in cars.
The researchers’ studies on estolides, begun in 2000, dovetail with an ARS push to develop biobased products that could help diminish U.S. dependence on foreign oil.
In March 2006, ARS and Peaks and Prairies, L.L.C., of Malta, Mont., entered into a cooperative research and development agreement to explore creating canola-based estolides.
ARS is the U.S. Department of Agriculture’s chief scientific research agency.
Source: USDA-news June 15, 2006.