Bio-Based Trivalent Phytate: A Novel Strategy for Enhancing Fire Performance of Rigid Polyurethane Foam Composites

Biomass phytic acid has potential flame retardant value as the main form of phosphorus in plant seeds. In this study, phytate-based flame retardants aluminum phytate (PA-Al) and iron phytate (PA-Fe) were synthesized and characterized. Subsequently, they were introduced into rigid polyurethane foam (RPUF) as flame retardants by one-step water-blown method. The results indicated that RPUF/PA-Fe30 exhibited the highest char residue of 22.1 wt%, significantly higher than 12.4 wt% of RPUF. Cone calorimetry analysis showed that the total heat release (THR) of RPUF/PA-Al30 decreased by 17.0% and total smoke release (TSR) decreased by 22.0% compared with pure RPUF, which were the lowest, demonstrating a low fire risk and good smoke suppression. Thermogravimetric analysis-Fourier transform infrared spectrometer (TG-FTIR) implied the release intensity of flammable gases (hydrocarbons, esters) and toxic gases (isocyanate, CO, aromatic compounds, HCN) of composites was significantly reduced after the addition of PA-Fe. The analysis of char residue indicated that the RPUF composites formed a dense char layer with a high degree of graphitization after the addition of PA-Al/PA-Fe, endowing RPUF composites with excellent mass & heat transmission inhibition effect and fire resistance in the combustion process.