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GREASE COMPONENTS
Base oil: Petroleum oils, silicone or synthetic diester/tetraester oil or fluorinated oils are mainly used as the base oil for grease. Although the lubricating properties of grease depend mainly on those of its base oil, the thickener used also has an effect. In general, low viscosity base oils are more suitable for high speed, low temperature applications and high viscosity base oils are more suitable for high temperature, heavy load applications.
| BASE OIL |
TEMPERATURE
RANGE |
OTHER PROPERTIES |
| Petroleum |
-25oF
to 250oF
(-32o to 121oC) |
Excellent load capacities (high film
stregth). Lower viscosity = high speed (dN) capability. |
| Diester/tetraester |
-65oF
to 350oF
(-54o to 177oC) |
Wide temperature range. Moderate film
strength. Oxidation resistant. |
| Silicone |
-100oF
to 400oF
(-73o to 204oC) |
Widest temperature range. Less film
strength than diester/tetraester. Tends to migrate giving
less rust prevention. |
| Fluorinated |
-30oF
to 550oF
(-34o to 288oC) |
Stable at high temperature. Chemically
inert. Ultra low vapor pressure (10-9 to 10-11 torr) gives
long life. Can be viscous at low temperatures. |
Thickener: Grease thickeners can be grouped into several families. Types used include compounds of metallic soaps (lithium, sodium), inorganic (silica gel, bentonite), heat resistant organic (urea, flouric) - or a mixture of several types. Important grease characteristics influenced by the choice of thickener are the dropping point (temperature at which the grease becomes sufficiently fluid to drip, affecting high-temperature performance), and the water solubility. In particular, sodium soap emulsifies with high humidity and cannot be used as a thickener when moisture is present.
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