Use Of DMSO For Aircraft Paint Stripping

Manufacturers of aircraft paint strippers shifted to alternative chemicals after methylene chloride was ruled out by the Environmental Protection Agency (EPA). They found NMP (N-methyl-2-pyrrolidone) and DMSO (Dimethylsulfoxide) to be alternatives worth considering.

Both are in the class of highly effective dipolar aprotic (unable to donate protons) solvents. However, tests ruled out the use of NMP because of its suspected toxic effects on the human reproductive system and consequent birth defects it caused. The EPA therefore specified NMP as an excluded chemical in their SARA III (Superfund Amendments and Reauthorization Act 1988 Title III) section 13 listing.

However, DMSO is not hazardous in this specific respect and so it is not covered in the above exclusions listing. That makes it a much safer alternative to NMP as a paint stripping solvent. Its properties also make it a significant constituent of an effective alternative aircraft paint stripping chemical mixture of cosolvents.

The best thing about DMSO is that it is biodegradable and biorenewable. It is also compatible for mixing with a wide range of cosolvents in aircraft paint stripping applications. Although toxic to the skin and for oral consumption in high amounts, it is significantly less so as compared to NMP. However, it is not a carcinogen. And yes, it is miscible with water, which allows the formulation to be rinsed.

DMSO effectively removes a wide range of paint and polyurethane top coats, waterborne and solventborne primers, and sealants from the exterior surfaces of all types of aircraft. An effective packaged formulation of aircraft paint stripping cosolvents would contain about 38 to 44 % DMSO and about 0.5% ethanolamine (which is an activator) combined initially together.

To the above mixture would be later added another thickener such as Methocel® 311 to the extent of 1%. About 19 % EEP (3-ethoxyethylpropionate) that is made by the Eastman Chemical Company will then be added to the mixture together with DBE (dibasic ester blends) to the extent of 19 to 30%.

DBE is a proprietary ingredient manufactured by Du Pont. Rhodasurf® DA-630, a product of Rhodia, will be added lastly to the above. The combined formulation is quite viscous (approximately 7000 centipoise).

Not only is DMSO environmentally safe, it is effective in both acidic and basic solvent formulations. DMSO basically acts by making the coating to swell up thereby lifting or tenting the paint on the surface of aircraft, which facilitates its removal quickly. The formulation comes packed in HDPE (high density polyethylene) containers. You will need to wear gloves made of butyl or nitrile rubber to protect your skin from coming into contact with the formulation.

DBSO based solvent formulations used to depaint the exterior surfaces of aircraft take about twice the time required by methylene chloride to strip the paint completely. DMSO is manufactured on a large scale by Gaylord Chemical Corporation.
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