Different Types of Grease

5/23/2014 How to Identify Different Types of Grease
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How to Identify Different Types of Grease
Noria Corporation
Tags: greases
What are the real differences in the various types
of grease?
Greases are primarily classified by their thickeners,
the most common being metallic soaps. Others
include bentonite clay, silica gel, polyurea and
inorganic thickeners.
Soap‑based greases are produced from three main
ingredients. One is the fatty material (animal or
vegetable), which is usually 4 to 15 percent of the
total, called the acid. The next is the base or
alkali, which is the opposite of an acid. Bases used
in making greases include calcium, aluminum,
sodium, barium and lithium, with 1 to 3 percent normally needed. The third portion is the fluid,
which can be selected from mineral oils, various types of synthetics, polyglycols or a never‑ending
combination of fluids.
A more complex structure can be formed by using a complexing salt. This converts the thickener
to a soap‑salt complex, hence the term complex grease. Complex greases offer a higher working
temperature of about 38 degrees C (100 degrees F) than normal soap‑thickened products.
Complex greases were developed to improve the heat resistance of soap greases, with the most
popular being lithium, aluminum, calcium and barium. These products exhibit a higher dropping
point (about 260 degrees C or 500 degrees F), with the exception of barium, which is about 218
degrees C (425 degrees F). The dropping point is the temperature at which the product turns from
a semi‑solid to a liquid. In other words, it is the point at which the lubricant may begin to separate
from the thickener.
Complex greases offer a higher working temperature than normal soap types and generally provide
outstanding oxidation resistance, although this is not true in all cases. They are also increasing in
popularity, with lithium and aluminum being the front-runners.
Inorganic thickeners such as clay and silica consist of spheres and platelets. They thicken fluids
with their large surface area. These products produce a very smooth non-melting grease that can
be made to perform very well when careful consideration is given to product application.
Polyurea is a type of non‑soap thickener that is formed from urea derivatives. It is not a true
polymer but rather a different chemical that has a thickening structure similar to soap. Polyurea
greases are very stable, have a high dropping point and give outstanding service life.
In terms of use, the lithium 12‑hydroxystearate greases are by far the most popular. These are
based on 12‑hydroxystearic acid, which is a fatty acid that produces the best lithium and lithium-
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complex greases.