Abstract
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.
Highlights
In the polyurethane system, rigid polyurethane foam (RPUF) has the advantages of convenient construction, low thermal conductivity, good compression resistance and low density, so it is widely used in building insulation, petrochemicals, transportation and household appliances [1–5]
The above results indicated that Phytic acid (PA)-Al/PA-Fe could promote the initial degradation of the RPUF composites and cross-link with the polyurethane matrix at medium and high temperatures to form a protective barrier, thereby improving the high-temperature thermal stability of the composites
scanning electron microscope (SEM) test showed that PA-Al/PA-Fe exhibited excellent compatibility with the RPUF matrix
Summary
Rigid polyurethane foam (RPUF) has the advantages of convenient construction, low thermal conductivity, good compression resistance and low density, so it is widely used in building insulation, petrochemicals, transportation and household appliances [1–5]. Two biobased flame retardants, aluminum phytate (PA-Al) and ferric phytate (PA-Fe) were prepared to modify RPUF This improves the effect of high content flame retardant on the matrix, and reduces the cost to a certain extent. Phytic acid is biomass with high phosphorus content, enhancing the flame retardant properties of polymers by promoting their carbonization [21]. On this basis, SEM-EDS, thermal conductivity tester, density measurement, thermogravimetric analysis, cone calorimetry, TG-FTIR and Raman spectroscopy were used to investigate the effects of PA-Al/PA-Fe on the physical properties, thermal stability, pyrolysis gas products and combustion characteristics of RPUF composites
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