ASTM D128 standard test methods for analysis of lubricating grease
3. Terminology
3.1 Definitions:
3.1.1 asphalt, n - a dark brown-to-black cementitious material in which the predominating constituents are bitumens.
3.1.1.1 Discussion - Asphalt can be a natural product or a material obtained from petroleum processing.
3.1.2 candle pitch, n - a dark brown-to-black, tarry or solid, by-product residue from soap and candle stock manufacture, refining of vegetable oils, refining of wool grease, or refining of refuse animal fats.
3.1.3 cup grease, n - any lubricating grease having physical properties, such as consistency and texture, suitable for its use in spring-loaded or screw-type lubricating cups.
3.1.3.1 Discussion - Cup greases are predominantly NLGI No. 3 or 4 calcium greases, but grease types other than calcium are also used.
3.1.4 degras (wool fat, wool grease, wool wax), n - a fat-like material comprised primarily of sterols, other higher alcohols, and fatty acids, obtained from the solvent extraction of sheep's wool.
3.1.5 free alkali, n - in lubricating grease, unreacted basic (alkaline) material present in the product.
3.1.5.1 Discussion - Many greases are made with a slight excess of alkali to ensure complete saponification. Free alkali is determined by acidification of a solvent-thinned specimen and back titration with standardized, alcoholic potassium hydroxide. It is expressed in terms of the predominating alkali and a mass % of the total grease composition (for example, mass % lithium hydroxide).
3.1.6 free fatty acid, n - in lubricating grease, unreacted carboxylic acid(s) present in the product.
3.1.6.1 Discussion - Some greases are made with a slight excess of carboxylic acid to ensure a non-alkaline product. Free fatty acid is determined by neutralization of a solvent-thinned specimen with standardized, alcoholic potassium hydroxide. Regardless of the actual composition of the carboxylic acid(s), it is expressed as free oleic acid and as a mass % of the total grease composition.
3.1.7 insolubles, n - in lubricating greases analysis, the material remaining after the acid hydrolysis, water extraction, and solvent extraction of soap-thickened greases.
3.1.7.1 Discussion - Consisting of such products as graphite, molybdenum disulfide, insoluble polymers, and so forth.
3.1.8 lubricating grease, n - a semi-fluid to solid product of a dispersion of a thickener in a liquid lubricant.
3.1.8.1 Discussion - The qualifying term, lubricating, should always be used. The term, grease, used without the qualifier refers to a different product, namely certain natural or processed animal fats, such as tallow, lard, and so forth.
3.1.9 mixed base, adj - in lubricating grease, the description of a thickener system composed of soaps of two metals.
3.1.9.1 Discussion - Although mixed-base grease can be made with soaps of more than two metals, in practice, such is rarely, if ever, encountered. All of the soaps need not be thickeners, although the major soap constituent will be one capable of forming a lubricating grease structure. Because the mixed soaps are seldom present in equal amounts. The predominant soap is referred to first.
3.1.10 montan wax, n - a wax-like material comprised primarily of montanic acid and its ester, higher aliphatic alcohols, and resins obtained from the solvent extraction of lignite.
3.1.11 neutralization number, n - of petroleum oil, the quantity of acid or base required to titrate to neutrality and expressed as equivalent milligrams of potassium hydroxide per gram of sample.
3.1.12 NLGI, n - National Lubricating Grease Institute.
3.1.13 NLGI number, n - a numerical scale for classifying the consistency range of lubricating greases and based on the Test Methods D217 worked penetration.
3.1.14 non-soap thickener (synthetic thickener, inorganic thickener, organic thickener), n - in lubricating grease, any of several specially treated or synthetic materials, excepting metallic soaps, that can be thermally or mechanically dispersed in liquid lubricants to form the lubricating grease structure.
3.1.15 residuum, n - a liquid or semi-liquid product obtained as residue from the distillation of petroleum and consisting primarily of asphaltic hydrocarbons.
3.1.15.1 Discussion - Also known as asphaltic oil, asphaltum oil, liquid asphalt, black oil, petroleum tailings, and residual oil.
3.1.16 rosin oil, n - a viscous, oily liquid obtained as a condensate when the residue (rosin) from turpentine production is subjected to dry, destructive distillation.
3.1.16.1 Discussion - Also used to describe specially compounded oils having a rosin base.
3.1.17 saponification, n - the interaction of fats, fatty acids, or esters generally with an alkali to form the metallic salt, which is commonly called soap.
3.1.17.1 Discussion - Soap thickeners are most often made by in situ saponification in the lubricating grease base oil. However, the use of pre-formed soaps is also common; dispersion is effected by mechanical means and usually with heat.NLGI Lubricating Grease Guide
3.1.18 single base, adj - in lubricating grease, relating to a thickener comprised of soaps of only one metal.
3.1.19 soap, n - in lubricating grease, a product formed in the saponification (neutralization) of fats, fatty acids, or esters by inorganic bases.
3.1.20 Soxhlet apparatus, n - a device, usually of glass, used to extract soluble material from a mixture of soluble and insoluble (generally solid) materials, by passing a volatile solvent through the sample and recirculating the solvent by refluxing.
3.1.21 tar, n - a brown or black, bituminous, liquid or semi-solid comprised primarily of bitumens condensed in the processing of coal, petroleum, oil-shale, wood, or other organic materials.
3.1.22 thickener, n - in lubricating grease, a substance composed of finely divided solid particles dispersed in a liquid lubricant to form the product's structure.
3.1.22.1 Discussion - The thickener can be fibers (such as various metallic soaps) or plates or spheres (such as certain non-soap thickeners), which are insoluble or, at most, only very slightly soluble in the liquid lubricant. The general requirements are that the solid particles be extremely small, uniformly dispersed, and capable of forming a relatively stable, gel-like structure with the liquid lubricant.
3.1.23 thimble, n - in Soxhlet apparatus, a closed-end porous cylinder used to hold the material to be extracted, usually made of thick matted filter paper but sometimes made of ceramic.
3.1.24 total fluid constituent, n - in lubricating grease analysis, the n-hexane-soluble material extracted from the lubricating grease sample.
3.1.24.1 Discussion - Typical materials include petroleum oil, non-petroleum fluid, soluble fats, and soluble additives.
3.1.25 total n-hexane-insoluble material, n - in lubricating grease analysis, that portion of grease (excluding free alkali) that is essentially insoluble in n-hexane.
3.1.25.1 Discussion - Typical materials include thickeners, fillers, inorganic salts, asphaltenes, or any combinations of these (also includes insoluble materials found in the analysis of contaminated grease). Free alkali content is generally insignificant.
3.1.26 unsaponifiable matter, n - in lubricating grease, organic materials, either added or found with fatty materials, which do not react during saponification.
