Oils, Greases and Emulsions

The resistance to motion that operates when one solid surface is moved tangentially with respect to another solid surface, with which it is in contact, is known as Frictional Resistance, and results in considerable loss of energy and damage to the contacting surfaces. 

The losses due to frictional resistance fonn a substantial part of the total energy consumption of mankind. In order to conserve the depleting energy reserves, it is essential that the frictional resistance be brought down to the optimum. Friction can be reduced by 

In addition to reducing energy losses and wear and tear of the moving surfaces, a lubricant is usually called upon to perform one or more of the following inter-related functions  

Depending upon the operating conditions and the lubricant characteristics, a lubricant may form a fluid film (- 1000 A thick) in between the moving surfaces thereby removing all points of contact between them (Hydrodynamic or Fluid Film Lubrication). Solid friction is completely substituted by fluid friction and the coefficient of friction (0.001-0.01) is governed by viscosity of the fluid. 

Under conditions of high load, low speed, or when the lubricant has a low viscosity, it may be squeezed out of position. Lubrication is then maintained by a very thin film (only a few molecules thick) of the lubricant adsorbed on the surface (Boundary Lubrication). The moving surfaces are not completely separated but their points of contact are considerably decreased. The coefficient of friction depends on the sticking characteristics (oiliness) of the lubricant and is much higher (0.05-0.15) than in the case of hydrodynamic lubrication. 

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The topic of specific gravity has been added to the chapter on Lubricating Oils, Greases and Emulsions. 

Chloroform is a volatile, low-molecular weight, lipophilic compound and a chlorinated trihalo-metheane. Most of the chloroform produced in the United States is used to make fluorocarbon 22 (HCFC 22) and the rest is produced for export and miscellaneous uses. In the past it was used as an inhalation anesthetic and as an extraction for, fats, oils, greases and other products, as a dry cleaning spot remover, in fire extinguishers, and as a fumigant. It is available as emulsions, spirits, tinctures, and chloroform water. Chloroform is also formed as a by-product of chlorination of water, wastewater, and swimming pool. Other sources include pulp and paper mills, hazardous waste sites, and sanitary landfills. 

A conventional emulsion polymer based on vinyl acetate has been modified by carboxylation (92). The carboxylated ethylene-vinyl acetate adhesive increases the adhesion to metal and polymer surfaces and the resistance to oil, grease, and water. The films are also acid, alkali, and UV resistant. Furthermore, the polymers are cross-linkable through the carboxylic groups. These adhesives can react with aminoplasts, phenolics, and epoxy resins for increased water and creep resistance. 

In industries that are bonding plasticized materials, there are some specific tests to measure for instance peel strength before and after accelerated aging test. The A and S suppliers, who know the raw materials included in their formulations, can tell quickly whether a given adhesive should be sensitive or not to oils, greases and plasticizers. Some adhesives are sensitive to oils (vinyl emulsion glues), some are not (epoxies, anaerobics, etc.). 

K-Flex dibenzoate esters are widely used as plasticizers for polyvinyl acetate emulsion systems. In these systems, K-Flex dibenzoate esters reduce set times, increase open time, increase film flexibility, reduce heat sealing tea eratures, and ia rove the dried film s resistance to oil, grease, and water. They also serve to enhance solution viscosities, often eliminating the need for other additives. K-Flex dibenzoate esters offer equal or superior performance to other recognized adhesive plasticizers. 

Emulsion cleaners These are emulsified chlorinated solvents and are kerosene based, suitable for mineral oils (petroleum and heavy petroleum greases) and deep-drawn components, using lead compounds as lubricants. They are also suitable for non-ferrous metals. 

Some of the commercial uses which the machine suggests are the recovery of oil from soap stock, the dehydration of crude petroleum and emulsions, the separation of amorphous wax from cylinder stock and the recovery of wool grease from waste scouring liquors. A brief description of the last application will make the commercial use of the machine plain. 

Water-in-oil emulsion — A type of emulsion in which droplets of water are dispersed throughout oil. It is formed when water is mixed with a relatively viscous oil by wave action. This type of emulsion is sometimes stable and may persist for months or years after a spill. Water-in-oil emulsions containing 50 to 80% water are most common, range in consistency from grease-like to solid, and are generally referred to as chocolate mousse . (See also Chocolate mousse, Emulsification, Oil-in-water emulsion.)... 

When the value of the interfacial tension is significantly less than 1 mN m 1, then we consider the measurement of ultra-low interfacial tension, which is common in liquid-liquid emulsification processes when effective surfactant solutions are used. The dynamic spinning drop tensiometer method is especially suitable for this purpose. Ultra-low interfacial tension measurement is important in the chemical industry because the cleaning of solid surfaces of dirt, grease, and oil the formulation of stable emulsions the recovery of petroleum, and other applications often rely on lowering the interfacial tension between immiscible liquids to ultra-low values by the use of surfactants. 

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