Grease, thickened with silica

In nonpolar liquids or oils thickened with silica certain additives cause a break-of the thickened gel or grease. The effect of polar compounds and of traces of water in the system have been studied by Wightman and Chessick (335). ... 

These are generally reserved for specialist applications, and are in the main more costly than conventional soap-based greases. The most common substances used as nonsoap thickeners are silica and clays prepared in such a way that they form gels with mineral and synthetic oils. Other materials that have been used are carbon black, metal oxides and various organic compounds. 

Hydrogels of silica were milled into oil with an oleophilic surfactant such as a long Chain quaternary ammonium- compound, dimethyldioctadecylammonium chloride, or metal soaps. Clays were used but the process also applied to fine silica (599). This was only one of many patents relating to grease thickeners made from bentonite-type clays (600). 

Silica was coated with a phenol-formaldehyde resin from acetone solution and cured and found to impart good shear stability when used as a grease thickener (608). 

Recently, greases have been developed in which chemically altered bentonite is used as a thickener instead of soap 10). The bentonite is purified by removal of silica and is altered chemically by reaction with alkyl amines. 

Stabilization of silica-thickened grease with basic aluminum stearate probably - involves adsorption of the aluminum on the silica with the fatty add anions attached (503). Silica fillers for elastomers are improved by rendering the surface organophilic with basic chromium complexes of the type... 

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