Bio‐Based Chitosan as a Green Flame Retardant for Rigid Polyurethane Foam Composites: Enhanced Flame Retardancy, Smoke Suppression, and Mechanical Performance With Experimental and Simulation Validation

ABSTRACT

Rigid polyurethane foam (RPUF) composites were modified with bio‐based chitosan (CS) as a green functional additive to replace conventional synthetic flame retardants for building insulation applications. The RPUF/CS composites were systematically characterized by FTIR, thermogravimetric analysis (TG), limiting oxygen index (LOI), cone calorimetry, smoke toxicity analysis, compression testing, and Abaqus finite element simulation. The optimal formulation with 6 wt% CS (RPUF/CS‐6) exhibited the highest initial decomposition temperature, maximum decomposition temperature, char residue, and activation energy among all four heating rates. LOI reached 24.3%, significantly higher than unmodified RPUF. Cone calorimetry at 50 kW/m ² showed that RPUF/CS‐6 reduced heat release rate (HRR) by 53.43%, total heat release (THR) by 25.31%, smoke production rate (SPR) by 58.33%, total smoke release (TSR) by 40.38%, and smoke density (Ds) by 23.06%, demonstrating significantly enhanced flame retardancy and smoke suppression performance. Compression tests combined with Abaqus simulation confirmed that CS incorporation substantially enhanced structural integrity and mechanical stability. By replacing synthetic flame retardants with natural polymer CS, this work achieves a unique combination of improved flame retardancy, smoke suppression, and mechanical performance. The experimental and numerical validation provides a robust basis for designing high‐performance, low‐fire‐risk, environmentally friendly RPUF composites. This cleaner production strategy offers a promising route for sustainable building insulation materials.