Ammonium polyphosphate@ZIF flexible polyurethane foam designed by the interface hydrogen bond network connection for thermal insulation and fire retardancy

The pursuit of multifunctional polymer foams that simultaneously integrate fire safety, thermal insulation, and smart features is becoming critically important for next generation energy and transport applications, yet achieving this remains a formidable challenge. Herein, a novel composite flame retardant (APP@ZIF), which closely combines the zeolite imidazolate framework (ZIF) and ammonium polyphosphate (APP) at the nanoscale through multiple physicochemical interactions (physical adsorption, electrostatic interaction and hydrogen bonding), and then loads it onto the cell wall of flexible polyurethane foam (FPUF). The material simultaneously delivers efficient fire protection, excellent thermal insulation, and infrared stealth performance. The interface interaction between APP@ZIF and FPUF was simulated by Materials Studio software. The flammability performance was systematically characterized through open-flame testing, horizontal combustion test, limiting oxygen index (LOI) measurements and cone calorimeter test. The results indicated that FPUF-3 exhibited excellent fire and smoke suppression effects, and its peak heat release rate (PHRR), total smoke production (TSP), and CO2 production are reduced by 34.1%, 57.1%, and 37.1%, respectively. It provides a novel approach for preparing lightweight, high-performance flame-retardant FPUF materials.