Types Of Greases
The metallic radical of the soap largely determines the characteristics of the greases the fatty radical having a secondary effect. Greases are therefore classified in terms of the metal they contain.

• Calcium Soap Greases
• Sodium Soap Greases
• Lithium Soap Greases
• Aluminium Soap Greases
• Mixed Soap Greases
• Complex Soap Greases
• Non- Soap Greases

Calcium Soap Greases

The conventional types (excluding the complex soap greases have a smooth buttery texture and are water resistant, with dropping points around 90- 100 ºC. They are water stabilized, that is , the water is present in the soap crystals as water of crystallization. The optimum amount of water varies considerably with the type of formulation, fatty material and mineral oil used, but is usually within the range of 0.5 – 1.3% by wt. at high temperatures the water is gradually lost and the soap structure is weakened. Consequently, calcium soap Greases are restricted to use at fairly low maximum temperatures about 50 – 60ºC. They all turn fluid after exposure to high temperatures and may separate into the oil and soap phases. Only those which contain other stabilizers besides water (e.g. wool grease) will regain their structure on cooling.

• Sodium Soap Greases

These are usually more or less fibrous in structure/ texture depending mainly on the nature of the fatty material, high unsaturation yielding very fibrous greases. They have high dropping points usually not less than 150ºC and sometimes as high as 200ºC and are useful for relatively high temperature service. Owing to the solubility of the soap in water they are not water resistant.

• Lithium Soap Greases

These greases first appeared during -the World War II and were made from Lithium Stearate preformed soap. Now a-days lithium hydroxy stearate greases made by saponification in situ from hydrogenated castor oil predominate. Depending on the composition Lithium greases are smooth or slightly grainy in appearance. They have the highest dropping point about 190ºC of the conventional greases and the highest service temperatures. They are water resistant, mechanically stable, and can be made with a greater variety of types of oil than other greases. Their versatility and wide operational scope especially in high-speed service has led to their use as Multipurpose greases to the displacement of earlier types of more specialized greases.

• Aluminium Soap Greases

Aluminium Greases have an attractive translucent smooth and polished appearance. The dropping points are low about 90ºC and the greases tend to become rubbery at high temperatures. They are almost invariably made from high viscosity oils and often incorporate polymers. Such products are water Resistant; stringy, and adhesive, and find application as chassis and gear lubricants. They are not recommended for rolling bearings.

• Mixed Soap Greases

A variety of mixture is used, the commonest being Sodium-Calcium and the greases are generally manufactured by saponifying the fatty materials with mixed alkalies derived from different metals. One of the soaps usually predominates and determines the general character of the grease, while the other modifies the structure in some way. This results for example, in changes in texture and improved mechanical stability.

• Complex Soap Greases

The normal soaps can be complexed with various inorganic salts, usually short-chain aliphatic compounds. The commonest type is a calcium soap –calcium acetate complex although many other combinations have been patented. The greases are water resistant and have very high dropping points, in the range 200 -300ºC. With EP additives incorporated they are encountered as steel mill greases. New greases have recently been introduced for multi-purpose.

• Non- Soap Greases

There are two main types, these intended for general industrial use and those for specialized applications. The former include greases thickened with silica and clay ( Bentonite) and organic derivatives,such as terephthalamates, diamido dicarbonyl and aryl substituted ureas. High temperatures, mechanical stability, water resistant etc. suggest that they are multipurpose greases with a wider scope than soap greases. However, they have not made any great impact on the market. The type used for specialized applications includes greases made from the dye stuffs indanthrene and phthalocyanine which are generally combined with synthetic fluids, such as diesters and silicones and hence are very expensive. One such product is claimed to operate between - 75ºC and + 320ºC.