Metal Finishing Guide Book

2013

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Table I: Physical Properties of Chlorinated Solventsa Properties Chemical formula Molecular weight Boiling point Freezing point TrichloriethylenePerchloroethylene C2HCI3 131.4 189oF 87oC –124oF –86.7oC Specific gravity 1.456 Density (lb/gal) 12.11 Density (kg/L) 1.456 Vapor density 4.53 Viscosity 0.54 Flash point None Flammable limits 8-9.2% (volume of solvent in air) (saturation) Kauri butanol value 129 Solubility (g/100g) Water in solvent 0.04 Solvent in water 0.10 Methylene Chloride C2Cl3 165.8 250oF 121.1oC –9oF –22.8oC CH2CI2 84.9 103.5oF 39.7oC –139oF –95oC 1.619 13.47 1.619 5.76 0.84 None None 1.32 10.98 1.32 2.93 0.41 None 14-22% 90 136 0.0105 0.015 0.17 1.70 cleaning as well as other applications. This policy also pointed out that worker exposure and environmental emissions of these solvents should be controlled properly and in accordance with other workplace, environmental, and consumer regulations established by the EPA and other agencies. The policy is particularly applicable, however, in cases where nonflammability is a critical prerequisite for safety and where effects on personal health and the environment are reduced to a minimum by engineering and operating design. Each of the three chlorinated solvents has its own advantages for specific applications, based on its physical profile (see Table I for physical properties). Trichloroethylene (TCE) is a clear, heavy liquid (12.11 lb/gal) with excellent solvency. Long recognized for its cleaning power, TCE boils at 189oF (87oC) and freezes at -124oF (-86.7oC). The high density of TCEs vapor (4.53 times that of air) assures low vapor loss and easy recovery from vapor degreasing systems. TCEs aggressive solvent action works well on the oils, greases, waxes, tars, lubricants, and coolants generally found in the metal processing industries. It is especially effective in removing difficult soils such as semicured varnish or paint films, heavy rosins, and buffing compounds. Perchloroethylene (PCE or perc, also called tetrachloroethylene) is a clear, colorless liquid with a distinctive, somewhat ether-like odor. It has the highest boiling point (250oF, 121.1oC) and freezing point (-9oF, -22.8oC), weight (13.47 lb/gal), and vapor density (5.76 times that of air) of the chlorinated solvents. The high boiling point of PCE makes it especially effective in removing high-melting pitches and waxes and for cleaning grossly contaminated parts. The high temperature of PCE vapors also permits complete and thorough drying of work by vaporizing moisture entrapped in porous metals, deeply recessed parts, and blind holes. Methylene chloride (MEC, also called dichloromethane) is a powerful and ver109

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