"What are the typical grease thickener properties for c […]
"What are the typical grease thickener properties for calcium-12 hydroxy or lithium-12 hydroxy? How can you determine which grease is appropriate for your application?"
Lithium 12-hydroxystearic acid has widely been considered a preferred fatty acid in the manufacturing of lithium-based grease thickeners. This fatty acid has had its application in calcium-based grease thickeners as well. Greases formulated with this acid will often be smooth with a buttery texture. They also tend to have a higher thickener content by weight of about 10-15 percent. The smooth texture and many of the other advantages derived from these thickeners is due to their webbed fibrous pattern, which is only visible on a microscopic scale.
Calcium 12-hydroxystearate grease is one of the most common types of anhydrous calcium-based greases. It has a dropping point of around 275 to 300 degrees F, with a maximum usable temperature of approximately 230 degrees F and average characteristics at low temperatures. When well-formulated, the grease normally has good oxidation and water resistance, but other additives may be necessary to protect against rust. Calcium 12-hydroxystearate is also generally compatible with many other greases as well.
The vast majority of lithium-based greases are formulated with 12-hydroxystearate soap for versatility. The dropping point for these greases is higher, around 350-400 degrees F. They also have good resistance to water, although the grease may soften and run when large quantities of water are present. The maximum usable temperature is around 250 degrees F, which is better or equal to most other grease types. Unlike calcium 12-hydroxystearate, lithium 12-hydroxystearate is less compatible with other greases.
When trying to decide which grease is best for your application, evaluate the top performance properties that will impact the application. Some of these properties have been mentioned already, including the dropping point, maximum usable temperature, water resistance and oxidation resistance. The usable temperature range is especially critical when the application will experience temperature extremes.
The grease's consistency will be important to consider in every application. It is determined by the base oil viscosity and the thickener concentration and type. Lithium-based greases remain very common in the industry (as much as 70 percent or more) for their overall performance. Other types of thickeners, like calcium 12-hydroxystearate, will be limited to specific purposes, such as for certain types of seals, chains and roller bearings.
It should also be noted that some greases have thickeners that are mixtures of both lithium and calcium. Other greases may even be manufactured with 12-hydroxystearate as the fatty acid. Much like any specialty grease formulation, these lubricants likely are not intended for multi-purpose applications. Be sure to reference the manufacturer's product data sheets for specific application recommendations.