Microencapsulated phase change materials functionalized with PBA for enhancing the flame retardancy of thermally regulated rigid polyurethane foam

Rigid polyurethane foam (RPUF), as one of the important materials for energy-efficient buildings, faces significant challenges in achieving multifunctionality, specifically the integration of flame retardancy, mechanical robustness, and thermal regulation. Phase change material (PCM), which store and release thermal energy through reversible phase transitions, have emerged as promising candidates for thermal regulation due to their high energy storage density and stable transition temperatures. Nevertheless, their practical application is often limited by flammability and leakage issues. To address these limitations, this study presents a novel phase change composite (MFPCM@PBA), synthesized by encapsulating n-octadecane (C18) within a melamine-formaldehyde resin shell via in situ polymerization, followed by in situ deposition of Prussian blue analogue (PBA) onto the shell surface. The resulting MFPCM@PBA were incorporated into RPUF to impart integrated flame retardant and thermal regulation functionalities. RPUF-5%MFPCM@PBA exhibited a limiting oxygen index (LOI) of 25.6% and demonstrated reductions in total heat release (THR) and total smoke production (TSP) by 34.4% and 46.7%, respectively, compared to unmodified RPUF. Furthermore, under continuous heating for 500 s, the central temperature of RPUF-5%MFPCM@PBA was 20 °C lower than that of RPUF. This work presents an effective strategy for constructing multifunctional polymeric foams with enhanced fire safety and thermal regulation, offering promising potential for applications in energy-efficient and flame-retardant building materials.