Highly thermally stable MOF-based flame retardant system for fire-safe and toxicity-suppressing rigid polyurethane foam

Metal-organic frameworks (MOF) as promising flame retardants are constrained in polymer applications due to their low thermal stability and mechanical strength. To tackle these challenges, biomass-modified steel slag (PSS) was utilized to develop a highly thermally stable MOF-based flame retardant system, designed to enhance the thermal stability, flame retardancy, and toxicity suppression properties of rigid polyurethane foam (RPUF). When combined with ammonium polyphosphate, the MOF flame retardant system significantly enhances the flame retardancy of RPUF, achieving the UL-94 V-0 rating. Cone calorimeter tests revealed that compared to pure RPUF, the total heat release values of RPUF/APP/MOF, RPUF/APP/PSS, and RPUF/APP/PSS@MOF decreased by 22.8 %, 25.1 %, and 24.5 %, respectively, highlighting their effectiveness in mitigating thermal hazards. Notably, RPUF/APP/PSS@MOF emitted the least CO during the later stages of combustion. The CO adsorption capabilities of MOF and PSS@MOF were analyzed and validated through molecular dynamics modeling and simulations. While MOF demonstrated good CO adsorption capacity due to its distinctive porous structure, PSS@MOF obviously outperformed MOF in toxic gas adsorption. This finding aligns with cone calorimeter test results, confirming its superior effectiveness in reducing toxic emissions during combustion. This study underscores the significant flame-retardant potential of combining biomass-modified steel slag with MOF materials, promoting efficient recycling of industrial waste and significantly enhancing the flame-retardant and toxicity-inhibiting capabilities of MOF. These findings pave new ways for developing sustainable, efficient, and high-value flame retardants, enhancing the fire resistance of polymer composites while addressing environmental sustainability challenges. • SS@PCM was synthesized from PDA and SS for high-value resource utilization. • SS@PCM's thermal stability is enhanced by adding steel slag and polydopamine. • Materials Studio simulated CO adsorption by MOF and SS@PCM. • The PHRR, THR, TSP and CO values of RPUF/APP/SS@PCM were significantly reduced.