Aluminum soap grease

Figure 18-12. Speed-dependent torque behavior of greases in a journal bearing, steel journal in bronze bearing load 3718 N, temperature 311 K (37.8 C). A Base oil 300 SUS at 37.8 C. B Aluminum soap grease.

Greases are also made from soaps of strontium, barium and aluminum. Of these, aluminum-based grease is the most widely used. It is insoluble in water and very adhesive to metal. Its widest application is in the lubrication of vehicle chassis. In industry, it is used for rolling-mill applications and for the lubrication of cams and other equipment subject to violent oscillation and vibration, where its adhesiveness is an asset. 

Aluminum sulfate is also used in sizing of paper, as a mordant in the dye industry, chemical manufacturing, concrete modification, soaps, greases, fire extinguishing solutions, tanning, cellulosic insulation, and in some baking powders. 

Commonly used repeUents for leather are sUicones, chrome complexes of long chain fatty acids, and fluorochemicals. Fluorochemical repeUents also provide repeUency to oUs and greases so that the treated leather resists staining. A water repeUent may also be a hydrophobic chemical insolubUized in the leather. A simple water-repeUent treatment consists of forming an aluminum soap in leather by the two-step process of applying a soap, and then an aluminum salt. 

Heavy-metal soaps (loosely called metallic soaps) are those formed by metals heavier than sodium (aluminum, calcium, cobalt, lead, and zinc). These soaps are not water soluble specific types are used in lubricating greases, gel thickeners, and in paints as driers and flatting agents. Napalm is an aluminum soap. See saponification detergent. 

Methods of analysis (ASTM D-128, IP 37) are available for the measurement of excessive acidity derived from oxidation. These methods cover conventional grease that consists essentially of petroleum oil and soap. Thus these test methods are applicable to many types but not all grease. The constituents covered by the test series are soap, unsaponifiable matter (base oil), water, free alkalinity, free fatty acid, fat, glycerin, and insoluble. A supplementary test method is also provided and is intended for application to grease that contains thickeners that are essentially insoluble in n-hexane and to grease that cannot be analyzed by conventional methods because of the presence of such constituents as nonpetroleum fluids or nonsoap-type thickeners, or both. These methods may not be applicable to grease analysis when lead, zinc, or aluminum soaps are present or in the presence of some additives such as sodium nitrite. 

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

Oxidation of individual hydrocarbons may be exemplified by the work of Medvedev (232) who has been studying these reactions for a number of years and has more recently investigated the effect of oxygen on polymerization reactions. Neutral phosphates of aluminum, tin or iron, tin borate, etc., were found to be suitable for the conversion of methane to formaldehyde at 500°C. A practical aspect of this research is represented by the homogeneous oxidation of petroleum stocks in the presence of naphthenates which was developed by Petrov into an industrial process to supply fatty acids for the soap making and grease making industry (298,299). Kreshkov oxidized methane to formaldehyde in the presence of chlorine and steam over chlorides of copper or barium or over vanadium pentoxide on carbon (179), but his yields were low. 

Grease Thickeners Grease has nearly identical properties to lubricating oils, with the exception of the inclusion of a thickener, which gives it a solid or a semisolid consistency. Thickeners are often made of soaps of lithium, sodium, aluminum, or calcium. Like base oils and additives, thickeners possess a myriad of positive and detracting lubricating properties. 

To illustrate the problem for the product developer, one only has to enumerate the soils and surfaces. The soils can vary from simple dust and hair to dirt, hard water spots, and fingerprints to hardened grease, soap scum, and excrement. Although the usual household cleaning tasks are concentrated in only two rooms of the house, kitchen and bathroom, the number of different surfaces encountered are many. In the U.S., for example, there may be Formica , ceramic tiles, grout, lacquered wood, vinyl flooring, painted surfaces, brass, stainless steel, enamel, porcelain, aluminum, chrome, glass, marble, methyl methacrylate, and other types of plastics. All of these materials may occur within only two rooms of the same home ... 

Figure 18-9. Roll testing of grease consistency. Gellants A. Lithium stearate. B. Lithium 12-hydroxystearate. C. Calcium tallow soap. D. Sodium tallow-stearate. E. Aluminum stearate. From data by Woods and Trowbridge [23].

Negative effects on stress-cracking behavior can also be caused by grease thickeners, such as metallic soaps based on lithium, sodium stearate, or lithium-12-hydroxystearate and lithium, barium, or aluminum complex soaps [965]. 

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