Lube-Tech
the private industry to emulate. The United State’s Department of Agriculture in cooperation with the United Soybean Board created the terms Biobased and Bio-preferred and has an extensive program that lists available biobased products and their manufacturers.
www.biopereffered.com and
www.usb.org. Figure 2 illustrates a number of retail packaged biobased products that are sold nationwide in large big box stores. These products are sold based on performance and price without overtly emphasizing the environmental adders that are only visible upon inspection of the packaging.
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.118 page 2
environmentally aware products. The expectations give the impression that all biobased products are supposed to be vegetable oil based and/or that all lubricants can be made from vegetable oils.
Figure 2: Biobased Retail Products Sold in Major US Big Box Stores4
While in Europe the emphasis has been primarily on biodegradability, in the US the focus is on renewability and petroleum substitution to the extent possible. As a result, since PAOs are considered biodegradable, in Europe they are preferred over non-biodegradable lubricants. But, PAOs are not biobased since they are not derived from renewable materials and in the US, they are not considered bio-preferred. Biobased lubricants in most cases are also biodegradable; whereas not all biodegradable lubricants are biobased.
Biobased Base Oils There appears to be a general misunderstanding among the end users about the base oils used in
Vegetable oils offer many inherently advantageous properties when used as lubricants, but they also have inherent limitations when compared with mineral or synthetic oils. As a result, there are vegetable oil derivatives such as simple and complex esters, estolides, and an array of other chemically modified oils that offer base oils for different end use applications. A thorough understanding of the properties of the base oil along with an appreciation of the performance requirements of the end use are essential in preparing a superior biobased product. Table 1 shows a list of vegetable oils with their select properties. For example, castor oil shows a superior oxidation stability and low temperature performance. The Oil Stability Index (OSI) is an American Oil Chemists’ Society (AOCS) official method Cd 12b-92 re-approved 2017. For castor oil the OSI is 105.13 hours which is the highest stability of all oils listed in this table. But, castor oil also has the lowest viscosity index of all vegetable oils at 85. So, if used as hydraulic fluid, for instance, it would present good oxidation stability and cold temperature performance, but it would also thin down excessively at high operating temperatures. This makes it unsuitable as hydraulic fluid if used by itself.
Vegetable oils are often chemically modified, mixed together, or extracted from genetically enhanced seed oils with higher built-in stability. So, a combination of vegetable oils could enhance the properties of the mixture of one or more vegetable oil. An understanding of the properties of each vegetable oil alone or as a mixture when considered as base oil for lubricants is important when formulating biobased lubricants.
Base oil developers have often sought out oils that could be used across the application spectrum. As a
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