Report on Scientific Basis for Paint Stripping: Mechanism of Methylene Chloride Based Paint Removers

Chemical paint strippers that include methylene chloride and phenol have been extensively used to remove coatings from metallic substrates. These strippers are inexpensive and remove polymeric organic coatings quickly and easily from a variety of metallic substrates without damage to the substrate. Their mechanism of action has not been adequately characterized. Herein we report changes in physical and molecular-level properties of five coatings upon exposure to components of the paint stripper including methylene chloride and phenol. The coatings studied were polyurethane topcoats and epoxy primers currently in military use, both clear films and fully pigmented films. The development and use of simplified formulations clear films of each coating was done. The coatings were characterized using DSC, TGA, solid state 1H- and 2H-NMR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and attenuated total reflectance FTIR. Our results show very different behavior for methylene chloride and phenol. Methylene chloride acts by penetrating the coating and enabling other solvents in penetrating the coating. These other solvents, in particular water and phenol, are responsible for coating degradation.