Inorganic Greases
Organo clay (bentone)
Commercial bentone powder used as a thickener is basically an organophillic montmorillonite type of clay. They are formed by slurrying in the bentone powder in a portion of the oil, pre-gelling by adding a dispersant and stirring, then heating to drive off the remainder of the dispersant. Finally, the oil is blended in to adjust to the proper consistency. Bentones have a buttery texture, virtually no melting point, good adhesiveness, fair mechanical stability and poor rust preventative properties. They are valuable in high temperature applications and can be used as a multipurpose grease. The greatest disadvantage occurs if maintenance is neglected and an offing-out or breakdown of the grease occurs. The end result is bentonite clay in the bearing which will cause a rapid catastrophic failure of the system.
Silica
Silca based greases display very good pumpability and can be used in a wide range of applications, including aviation and at very high temperatures. The lack of fibrous structure can, however, result in excessive oil separation under pressure. This happens for example in centralized lubrication systems.
