Fire-Retardant, Self-Extinguishing Inorganic/Polymer Composite Memory Foams

Polymeric foams used in furniture and automotive and aircraft seating applications rely on the incorporation of environmentally hazardous fire-retardant additives to meet fire safety norms. This has occasioned significant interest in novel approaches to the elimination of fire-retardant additives. Foams based on polymer nanocomposites or based on fire-retardant coatings show compromised mechanical performance and require additional processing steps. Here, we demonstrate a one-step preparation of a fire-retardant ice-templated inorganic/polymer hybrid that does not incorporate fire-retardant additives. The hybrid foams exhibit excellent mechanical properties. They are elastic to large compressional strain, despite the high inorganic content. They also exhibit tunable mechanical recovery, including viscoelastic "memory". These hybrid foams are prepared using ice-templating that relies on a green solvent, water, as a porogen. Because these foams are predominantly comprised of inorganic components, they exhibit exceptional fire retardance in torch burn tests and are self-extinguishing. After being subjected to a flame, the foam retains its porous structure and does not drip or collapse. In micro-combustion calorimetry, the hybrid foams show a peak heat release rate that is only 25% that of a commercial fire-retardant polyurethanes. Finally, we demonstrate that we can use ice-templating to prepare hybrid foams with different inorganic colloids, including cheap commercial materials. We also demonstrate that ice-templating is amenable to scale up, without loss of mechanical performance or fire-retardant properties.