Development of two methods to evaluate lubricating greases using a rheometer

Abstract

Lubricating greases are crucial for both industry and every day applications. Lubrication has become a natural part of all moving equipment and lubricating grease plays an important role in keeping different machinery running without failure. Even if it is widely known that grease is vital for many devices, deep and specific knowledge of how grease behave in terms of rheological stresses is scarcely found. The scope of this project was to investigate and develop a standard method of conducting rheological measurements on lubricating greases. Two analytical methods to evaluate apparent viscosity and flow point were developed and evaluated. It was found that different greases did have measurable differences and that the methods evaluated could assist in comparing different greases to each other as well as in selecting the best grease for specific equipment. At higher temperatures a local minimum for both apparent viscosity and flow point was found. The root of this minimum is probably found in the thickener system of lubricating grease. The development of a new standard method for measurements of lubricating greases requires further investigation of why grease behave the way it does under rheological stress.