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Steel slag (SS) as solid waste, has low resource utilization efficiency and seriously endangers environmental safety and human health. To explore the potential utilization value of SS and address the flammability challenge of rigid polyurethane foam (RPUF), with a novel flame‐retardant system composed by SS and dimethyl methyl phosphonate (DMMP) was explored. The DMMP/SS system effectively improved the high temperature stability of the RPUF composites. When the mass ratio of SS and DMMP was 1:1, the limiting oxygen index of RPUF/DMMP/SS reached 23.1 vol% and UL‐94 vertical combustion tests passed V‐2 level. Upon incorporation of 15 wt% DMMP, the initial decomposition temperature (T−5 wt%) reduced to 165.3°C, a decrease of 32.2%, while the Tmax2 and residue yield at 700°C exhibited negligible alteration. The peak heat release rate of RPUF/DMMP/SS composite (118.20 W g−1) was 11.02% lower than that of pure RPUF, indicating the significant enhancement of fire safety of the composites. Results confirmed that a synergistic flame‐retardant mechanism was existed between DMMP and SS in enhancing the fire safety of RPUF composite. Introducing a 20 wt% SS content reduces the ID/IG ratio to 1.85, thereby markedly enhancing its heat resistance. This work provides a new application field of SS and paves a novel approach to enhance fire safety of polymers. [ABSTRACT FROM AUTHOR]

Iron tailings (ITS), as solid decay absolved afterward beneficiation, are adverse to the environment. ITS to prepare zinc‐containing mesoporous silicate (MAO‐Zn) by a calcination‐crystallization method are used. An admixture of ammonium polyphosphate (APP) and MAO‐Zn can solve the problem of poor flame retardancy in rigid polyurethane foam (RPUF), giving them higher thermal stability and lower heat release. The total heat release rate and smoke factor values exhibited by RPUF‐3 are 24.52 MJ m−2 and 234.29 MW m−2 respectively, a decrease of 38.45% and 29.60% respectively compared to pure RPUF. Lower combustible and toxic gas release intensities are in RPUF‐3. Meanwhile, RPUF‐3 possesses enhanced compactness char residue with higher graphitization degree, endowing RPUF‐3 with excellent fire observed performance. This work demonstrates the potential of ITS in the fire retardancy field. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Using phytic acid (PA) and piperazine (Pi) as raw materials, piperazine phytate (PA‐Pi) was fabricated by simple ionic reaction. Furthermore, A series of rigid polyurethane foam/piperazine phytate (RPUF/PA‐Pi) composites were prepared by one‐step water‐blown technology. Thermogravimetric (TG) results showed that the addition of PA‐Pi improved the thermal stability of RPUF/PA‐Pi composites at high temperature. At 700°C, RPUF/PA‐Pi20 exhibited the highest carbon residue of 25.8 wt%. Cone calorimetry and smoke density tests suggested that PA‐Pi could reduce the heat and smoke release during combustion process of the composites, thus reducing their fire hazard. Thermogravimetric‐Fourier transform infrared spectroscopy (TG‐FTIR) indicated that PA‐Pi significantly inhibited the release of toxic gases (isocyanate compounds, aromatic compounds, CO and HCN) and flammable gases (hydrocarbons and esters) during the decomposition process of RPUF/PA‐Pi composites, effectively improving fire performance of the composites. Scanning electron microscope (SEM), Raman and Fourier transform infrared spectroscopy (FTIR) were used to characterize the carbon residue of RPUF/PA‐Pi composites. The results showed that PA‐Pi could promote the formation of dense carbon layer of composites and effectively prevented heat and mass transfer in the combustion process. [ABSTRACT FROM AUTHOR]

Melamine–formaldehyde resin-microencapsulated ammonium polyphosphate (MFAPP) was prepared by in situ polymerization using melamine–formaldehyde (MF) resin as the shell material. MFAPP was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), which confirmed its successful fabrication. MFAPP was further introduced to prepare rigid polyurethane foam/microencapsulated ammonium polyphosphate composites (RPUF/MFAPP). The flame retardancy, water resistance, physical properties, and thermal stability of RPUF/MFAPP were compared with virgin RPUF and RPUF/APP composite. RPUF/MFAPP30 possessed excellent flame retardancy. Even after immersion in water for 15 days, RPUF/MFAPP30 achieved V-1 rating in UL-94 test with limiting oxygen index (LOI) of 21.3 vol%, which was better than that of RPUF/APP30 with equivalent APP loading. The compressive strength of RPUF/MFAPP30 was 0.295 MPa, which was 13.5% higher than that of RPUF/APP30. Thermogravimetric analysis-Fourier transform infrared spectroscopy (TGA-FTIR) was applied to investigate gaseous products of the decomposition process for RPUF/APP and RPUF/MFAPP. It was found that the intensities of CO2, isocyanate compounds, and CO for RPUF/MFAPP were lower than the values for RPUF/APP, indicating superior fire safety of RPUF/MFAPP. SEM and Raman spectra confirmed that RPUF/MFAPP30 possessed more compact char residue with higher thermal resistance, which was thus better able to inhibit mass and heat transmission in combustion. Consequently, a possible gas–solid flame-retardant mechanism of the RPUF/MFAPP composite was proposed. [ABSTRACT FROM AUTHOR]