Under the Massachusetts Toxics Use Reduction Act, manufacturing companies in MA have been challenged to find replacements for halogenated solvents that meet performance demands for removing oil, grease, wax, paint, dyes, or adhesives. Surface preparation and cleaning operations are usually performed through immersion or vapor contact.

Halogenated solvents, particularly trichloroethylene (TCE), n-propyl bromide, perchloroethylene (PCE), and methylene chloride, historically dominated the market of cleaning agents for these industries. Unfortunately, regrettable alternatives such as trans-dichloroethylene, hydro-chloro-fluorocarbons, and hydro-fluoro-ethers are gaining traction in the market.

Over three decades, the Toxics Use Reduction Institute (TURI) has identified and tested several safer replacements for halogenated solvents. We showcase successful examples and outline future development pathways toward achieving zero use of halogenated solvents in cleaning products and processes.

There are proven alternatives for metal degreasing, including terpenes, alcohols, ketones, acetates, and semi-aqueous formulations in ultrasonic processing. Performance evaluations conducted by TURI indicate that aqueous degreasing alternatives meet performance criteria for various contaminants and parts configurations.

On the other hand, the industry still prefers halogenated solvents for vapor-degreasing. Greener solvents with similar physicochemical characteristics they consider relevant can present additional hazards, including flammability, that create new costs and concerns. Enclosed vapor degreasing is expected to eliminate harmful solvent exposure for workers; however, the capital expenditure required for equipment often impedes its adoption.

Preliminary work indicates that cold plasma is an effective and safer alternative to vapor degreasing in some applications. The capital investment in cold plasma equipment is accessible enough to be covered by operational savings achieved by eliminating solvent use and disposal costs.

Gabriel Salierno

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