What chemical breaks down polyurethane?

Several chemicals can break down polyurethane, depending on whether you want to dissolve uncured liquid or strip cured solid polyurethane. For uncured or freshly applied polyurethane, strong solvents like methylene chloride, which is the active ingredient in many heavy-duty paint strippers, will dissolve it quickly. Other chemicals that break down polyurethane include acetone, methyl ethyl ketone, toluene, xylene, and dimethylformamide, which soften and dissolve the film. For cured polyurethane finishes on wood, chemical paint strippers containing methylene chloride, N-methyl-2-pyrrolidone, or benzyl alcohol are used to break down the crosslinked polymer so it can be scraped off. Isopropyl alcohol can soften water-based polyurethane somewhat but is less effective. For polyurethane foam, chemicals like glycolysis agents using diethylene glycol at high heat break it down for recycling. Strong acids and bases can also degrade polyurethane over time, as can prolonged exposure to UV and oxidation. In the environment, polyurethane slowly breaks down via hydrolysis and microbial action, though very slowly over decades. Always use chemical strippers with gloves, respirator, and ventilation because these chemicals are harsh and toxic.