Phytic Acid/Sodium Alginate Coating to Enhance Flame Retardancy of Rigid Polyurethane Foam: A Novel Strategy for Fire Safety

The precursor composed of phytic acid (PA) and sodium alginate (SA) was fabricated using the sol-gel technique and subsequently applied as a coating on the surface of rigid polyurethane foam (RPUF). PA/SA aerogel was obtained using freeze-drying technology to enhance the fire resistance and flame-retardant properties of the RPUF. Subsequent testing revealed that a 0.5 mm thick aerogel coating effectively enhances the flame retardancy of the composite. Limiting oxygen index (LOI) of the composites stands at an impressive 30.4 vol%, and it attains the V-0 rating in UL-94 vertical combustion testing. The Peak heat release rate (PHRR) measures 356.62 kW/m2, indicating a 27.60% reduction compared to that of pure RPUF. Thermogravimetric analysis shows a residual char residue of 20.78 wt%, representing a 52.46% increase compared to the pristine sample. Parameters such as the PHRR and fire growth index (FGI) exhibit significant reductions. This novel aerogel coating significantly enhances the fire safety of RPUF, effectively broadening applications of RPUF.