Surface tension apphcations

The low surface tension of highly fluorinated organic compounds is commercially important for their appHcation in surfactants, antisoiling textile treatments, lubricants, and specialty wetting agents. 

Foam Inhibitors. Methyl sihcone polymers of 300-1000 mm /s(= cSt)) at 40°C are effective additives at only 3—150 ppm for defoaming oils in internal combustion engines, turbines, gears, and aircraft appHcations. Without these additives, severe churning and mixing of oil with air may sometimes cause foam to overflow from the lubrication system or interfere with normal oil circulation. Because sihcone oil is not completely soluble in oil, it forms a dispersion of minute droplets of low surface tension that aid in breaking foam bubbles. 

Nitrile latices are used ia a wide variety of appHcations, including production of dipped nitrile mbber products. In the principle use of paper saturation, adhesives and fiber bonding, small particle size and optimum surface tension is desirable to achieve rapid penetration and setup or dryiag. 

Because of the complexity of designs and performance characteristics, it is difficult to select the optimum atomizer for a given appHcation. The best approach is to consult and work with atomizer manufacturers. Their technical staffs are familiar with diverse appHcations and can provide valuable assistance. However, they will usually require the foUowing information properties of the Hquid to be atomized, eg, density, viscosity, and surface tension operating conditions, such as flow rate, pressure, and temperature range required mean droplet size and size distribution desired spray pattern spray angle requirement ambient environment flow field velocity requirements dimensional restrictions flow rate tolerance material to be used for atomizer constmction cost and safety considerations. 

Antifog agents like fatty acid esters are used to avoid the formation of water droplets on the film under condensation conditions, e.g., in cling film apphcations at the transition from room temperature to a refrigerated warehouse. The antifog agent is hydrophilic and reduces the surface tension of droplets so that a uniform water film does not impair the clarity of the chng film [23]. 

Unique surface properties further distinguish silicones from other materials. The low surface tension of sihcone fluids makes them ideal for apphcations such as paper release agents, fiber lubricants, textile hand modifiers, mold release agents, antifouling materials, and water repellents. In fact, sihcones have been used in foam control and as anticaking aids, corrosion inhibitors, emulsifiers, lubricants, conditioners, and gloss enhancers—all because of their special surface properties, see also Polymers, Synthetic. 

It is dear from the discussion in this section that great care needs to be taken in the computation of two-phase flows that involve surface tension forces. At present, most commerdal software has algorithms that lend themsdves to generahty of apphcation, speed of solution and robustness rather than accuracy for the particular flows of... 

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