Lithium used to be the preferred grease for most applications, polyurea based greases are now the top shelf greases. Lithium greases are cheaper and still one of the most popular greases made.
Would it be good to use polyurea based grease on our sleds? Is it expensive?
What brands offer this polyurea based grease ?
From what I have read so far you better be right on the type of Polyurea grease or you can have compatibility issues:
The compatibility of polyurea greases with soap-thickened greases is probably the most debated area of grease compatibility today. Greases based on simple lithium soaps (lithium stearate or lithium 12-hydroxystearate) and lithium complex soaps (containing simple soap and a complexing agent, such as lithium azelate) may or may not be compatible with polyurea greases. This is because of the wide variety of materials that can be reacted to form a thickener that is termed polyurea. Some polyurea thickeners are completely compatible with lithium and lithium complex thickeners, while other polyurea thickeners are definitely incompatible with the lithium and lithium complex thickeners.
It is necessary to perform compatibility testing on combinations of these greases to determine whether the greases can be mixed in service. It is incumbent upon the user of the greases to verify compatibility when making a change from one product to another. Most grease suppliers have data on certain grease combinations or are willing to perform the required testing for their customers.
To help users understand the implications of mixing greases, ASTM International (formerly the American Society for Testing and Materials) Committee D02.G developed ASTM D6185 Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases in 1997. This document details the procedure for evaluating the basic compatibility of greases, which is determined by measuring the dropping point, the mechanical stability and the change in consistency of the mixture upon heating.
Greases are considered to be compatible if the following conditions are met:
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The dropping point of the mixture is not significantly lower than that of the individual greases.
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The mechanical stability of the mixture is within the range of consistency of the individual greases.
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The change in consistency of the mixture following elevated temperature storage is within the range of the change in consistency of the individual greases following elevated temperature storage.
Once two greases are determined to be compatible in the above three areas, further testing to determine the impact on other performance parameters of the products may be warranted. Any test that is designed for measuring grease performance may be used on a mixture of greases to determine the effect on that parameter when the greases are mixed. The tests that are conducted should be agreed upon between the user and grease supplier to assure that the properties that are critical to the proper function of the product in service are covered. The full text of ASTM D6185 is available from ASTM International at
www.astm.org.
About the Author
David Turner works for Shell Global Solutions Inc. and is the co-chairman of the National Lubricating Grease Institute’s technical committee. To learn more about NLGI, visit
www.nlgi.org.
Full article:
http://www.machinerylubrication.com/Read/1865/grease-compatibility
