The DoD has supported the reformulation of military coating systems to increase solids loading or to eliminate hazardous solvents. In some cases, the DoD has approved waterborne paint systems for military application or selected solvents because they are not listed as hazardous air pollutants (HAP). Regulators are now considering some of the non-HAP solvents for future regulatory constraints. SERDP and ESTCP have focused attention on alternative coating formulations and processes that are sustainable.
In addition to being used in painting processes, solvents are also used for many depaint or paint stripping processes. Methylene chloride had been the solvent of choice for paint stripping, but it is heavily regulated. Other solvents like N-methyl pyrrolidone (NMP) have been used for dip tank depainting, but the tanks are heated and NMP itself is under scrutiny as a hazardous material. Other solvent options for depaint include a variety of benzyl alcohol formulations which are not as effective and tend to be more labor intensive. SERDP and ESTCP have investigated the mechanisms involved in solvent depaint and have considered several paint stripping technologies that involve physical rather than chemical processes.
The synthesis and formulation of energetic materials often require significant quantities of hazardous or toxic solvents. These solvents, if contaminated with energetic material, are difficult to recycle and can become a hazardous waste stream. SERDP and ESTCP are investigating processes that eliminate, reduce, or recycle solvents. Solventless synthesis is the ultimate goal and is the topic of several investigations.