Flame retardant rigid polyurethane foam composites based on iron tailings and aluminum phosphate: A novel strategy for utilizing industrial solid wastes

To widen the application field of iron tailings (ITs) and explore ITs potential use-value, ITs and aluminum phosphate (AHP) were introduced to prepare flame-retardant rigid polyurethane foam (FR-RPUF) composites. The chemical composition and mineral composition of ITs were investigated by X-ray diffraction, X-ray fluorescence. The flame retardancy, thermal stability, combustion performance and gas-phase products of FR-RPUF composites were investigated by limiting oxygen index, underwriters laboratories vertical burning test (UL-94), thermogravimetry (TG), cone calorimetry and thermogravimetric-infrared spectrometry (TG-FTIR). TG confirmed that ITs could effectively improve the thermal stability of FR-RPUF composites at high temperature. Cone calorimetry implied that ITs could significantly reduce heat release and toxic smoke release and thus improve the fire safety of the composites. TG-FTIR indicated that ITs effectively reduced the release intensity of hydrocarbons, aromatic compounds, CO, isocyanates and esters. Scanning electron microscope and Raman spectra showed ITs could improve the compactness and graphitization degree of the char residues for FR-RPUF composites.