Upcycling of Disposable Face Masks into Water‐Resistant and Flame Retardant Foams

Abstract The global rise in single‐use face mask waste during the pandemic has created an urgent need for sustainable valorization pathways. Here, we report a solvent‐based route transforming mask wastes into lightweight and robust foams that are water‐resistant and flame‐retardant. The entire disposable mask—including nonwoven layers, the ear‐loop fibers, and the metal wire—is successfully recycled. The method uses n‐octadecane as a recyclable solvent to dissolve nonwoven layers and enables solvent removal and full recovery through ethanol‐based separation. Foams prepared by phase‐separation of solutions of polypropylene (PP) are reinforced by the incorporation of mildly processed ear‐loop fibers. The composite foams exhibit a tunable density and porous architecture, good mechanical performance, and significant hydrophobicity. In addition, the application of a tannic acid (TA)–Fe coating endows the foams with enhanced flame retardancy. This work achieves a high overall mass upcycling rate of 91%, and life cycle assessment (LCA) reveals a competitive carbon footprint and a material circularity indicator of 0.39 for the foams thanks to the carbon retained within the technosphere. The flexibility in material composition, coupled with solvent recyclability and simple processing, offers a scalable route for mask waste valorization and provides inspiration for transforming multi‐component wastes into functional materials.