Trichloroethylene (TCE) is an organochloride compound, a clear, colorless, and non-flammable liquid. This compound is recognizable by its slightly sweet, chloroform-like odor and its powerful ability to dissolve fats, greases, and oils. TCE’s unique combination of chemical stability and solvent strength established its reputation as a highly effective industrial solvent after its commercial production began in the 1920s. Today, while its use is heavily regulated due to its toxicity and environmental persistence, it remains a common chemical agent in manufacturing. The main applications of TCE fall into two categories: its use as a solvent for cleaning and its use as a building block chemical for other compounds.
Primary Industrial Application: Vapor Degreasing
Vapor degreasing represents the most significant current use of trichloroethylene as a solvent in industry. This process is a method of precision cleaning used to remove soils like cutting fluids, machining oils, and metal chips from manufactured parts. TCE is particularly suited for this task due to its high solvency, indicated by a high Kauri-Butanol (KB) value, and its relatively low boiling point of approximately 87.2 degrees Celsius.
The process involves suspending contaminated metal parts in a chamber above boiling TCE, which generates a dense solvent vapor blanket. When the hot vapor contacts the cooler part, it immediately condenses into a pure liquid solvent, which physically dissolves the surface contaminants. This clean, condensed solvent continuously washes over the part, carrying the oils and greases back into the boiling sump below. The parts emerge clean and dry without the need for a separate rinsing or drying step.
Industries that manufacture high-precision components rely heavily on this method. The aerospace industry uses it to clean jet engine parts, while the automotive sector employs it for transmission components and brake systems. Electronics manufacturing utilizes vapor degreasing to clean printed circuit boards and other sensitive electronic components.
Other Current Industrial and Chemical Manufacturing Roles
Beyond its role as a cleaning agent, trichloroethylene is now predominantly used as a chemical intermediate in closed-system manufacturing processes. This means the TCE is consumed in a chemical reaction to create a new product, rather than being released as a solvent. A large percentage of modern TCE production is dedicated to this purpose, particularly in the synthesis of hydrofluorocarbon (HFC) refrigerants.
TCE acts as a feedstock in the production of compounds like HFC-134a (1,1,1,2-tetrafluoroethane), a common refrigerant used in mobile air conditioning and other cooling systems. The chemical process uses TCE as a starting material, which undergoes sequential fluorination and hydrofluorination reactions to replace its chlorine atoms with hydrogen and fluorine. This closed-loop chemical manufacturing is distinct from solvent use.
TCE also functions as a specialized solvent in certain extraction processes, such as the removal of waxes, tars, and oils from specific materials. It is sometimes used as a component in various commercial formulations, including specialized adhesives, paint strippers, and industrial varnishes. These uses represent a smaller fraction of its overall consumption.
Historical and Discontinued Applications
Trichloroethylene has a diverse history of applications that have been largely phased out or banned in many regions due to growing awareness of its toxicity.
Medical Uses
One of its most notable former uses was in medicine as an inhalational general anesthetic and analgesic. Marketed under brand names like Trilene, it was frequently used for pain relief during childbirth and minor surgical procedures until the 1980s. Its medical use declined as newer, safer anesthetic agents, such as halothane, were developed, offering faster induction and recovery times for patients.
Industrial and Consumer Solvents
In the early to mid-20th century, TCE was a common solvent in the dry cleaning industry for removing spots and stains from fabrics. Its use in this capacity was largely supplanted by perchloroethylene (PCE) by the 1950s, which was considered less damaging to certain textiles.
TCE was also widely employed as an extraction solvent in the food industry, used to decaffeinate coffee beans and extract vegetable oils from source plants like soy and coconut. The United States Food and Drug Administration banned these food-related uses in 1977 due to health concerns over residual solvent in the final products.
It was also a common ingredient in numerous household products, including typewriter correction fluid, paint thinners, and general-purpose spot removers. These consumer applications were broadly discontinued as regulations tightened and manufacturers sought less hazardous alternatives.