Published: Jan 2009
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IN THIS CHAPTER WE REVIEW THE TECHNOLOGY of lubricating greases. Because of their distinct physical form relative to liquid lubricants, greases are used in specialized applications, such as roller bearings and slow speed gear systems, where a liquid lubricant either cannot be used or has inadequate performance. Composition, chemistry, properties, manufacture, and methods to produce lubricating greases are discussed. The chapter also includes discussion pertaining to selection criteria, testing requirements, and handling and disposal of greases. We close the chapter with examples of grease formulations. The use of animal fat in combination with lime, a crude form of the modern lubricating grease dates back to 1400 B.C. . In fact, the word “grease” is derived from the Latin word “crassus” for fat. Lubricating grease is one of the oldest lubricants used by man. The use of the animal fat for lubrication continued until the late 19th/early 20th century when mineral oil-derived greases were developed. This occurred after the discovery of petroleum in 1859. Incidentally, in this chapter, grease and lubricating grease and oil and fluid are interchangeable terms and imply the same. Mineral oil thickened with calcium carboxylate (lime soap) was the first grease that was marketed in volume. This was followed by aluminum stearate grease, sodium soap grease, calcium complex soap grease, and lithium and barium soap greases. A great break through occurred in 1942 when it was discovered that lithium 12-hydroxystearate-derived greases possess superior properties. The evolution of the lubricating greases is depicted in Fig. 10.1. One way to look at the timeline is that a particular lubricating grease had some inherent deficiencies; hence another grease was developed to overcome them.