Recent Advances in Flame-Retardant Flexible Polyurethane Foams

Flexible polyurethane foam (FPUF) is extensively applied in multiple applications, including automotive, construction, furniture cushioning, and transportation seating, due to its outstanding mechanical properties, sound absorption, breathable characteristics, and versatility. However, FPUF is highly flammable and releases significant quantities of smoke and harmful gases when burned, which presents considerable safety hazards and has led to extensive research into flame retardant solutions. This review covers the development of both conventional and bio-based flame-retardant agents, including reactive-type and additive-type FRs, and surface coating methods, with a focus on their preparation, characterization methods, and underlying flame retardant mechanisms. Additionally, innovative flame retardant technologies, particularly surface coatings, are discussed in terms of their impact on thermal stability, mechanical performance, and smoke toxicity reduction in the resulting FPUFs. The review also highlights future research priorities and significant challenges, including environmental concerns, cost-effectiveness, and durability. Future research will need to focus on improving flame retardant efficiency while also considering the environmental impact and recyclability of materials, aiming for the green and sustainable development of FPUFs.