Reducing the flammability of kapok fiber (KF) is an important strategy to increase its applicability. In this work, the phosphorylation of KF with ammonium dihydrogen phosphate (ADP) was used to reduce its flammability, the conditions of phosphorylation reaction were studied in detail, and the chemical groups, crystalline structure, thermal stability, heat release capability, flammability and charring ability of phosphorylated KF were analyzed. KF showed significantly higher phosphorylation level than cotton, and its phosphorylation greatly depended on ADP and urea dosage, reaction temperature and time, and pH. Urea addition, pH 6, 150 ℃ and 1 h rendered high phosphorylation with acceptable whiteness. Phosphorylated KF exhibited good char-forming, low heat release and excellent flame retardant performances during thermal degradation and combustion as evidenced by thermogravimetric, microcalorimetric, vertical combustion and combustion residue morphology analyses. The residue rate of phosphorylated KF subjected to thermal degradation exceeded 50% in nitrogen, and 25% in air. This investigation demonstrates that phosphorylated KF is an intrinsically flame retardant material. Graphic abstract
Nanowires, nanosheets, and microflowers of nickel ammonium phosphate (NiNH4PO4·H2O) were synthesized by a mixed solvothermal method and used to improve the flame retardancy of epoxy resin (EP). The solvent concentration and surfactant content were found to play a key role in nucleation and growth of NiNH4PO4·H2O. The structure of NiNH4PO4·H2O was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The flame retardancy, thermostability, mechanical properties, and flame retardancy mechanism of EP/NiNH4PO4·H2O composites were analyzed using the limiting oxygen index (LOI), cone calorimetry (Cone), mechanical property tests, thermogravimetric analysis, and thermogravimetric–Fourier transform infrared spectroscopy. The results indicated that NiNH4PO4·H2O has proper thermal stability and greatly improves the flame retardancy of EP. The nanosheets outperformed the other morphologies; the EP/5% NiNH4PO4·H2O nanosheets have an LOI of 35.2%, which exceeds that of pure EP (24.7%). Furthermore, Cone showed that these nanosheets have the lowest peak heat release rate and peak smoke production rate, which are 69.1% and 36.5% lower than those of pure EP, respectively. NiNH4PO4·H2O can promote the formation of a stable char layer and release nonflammable gases, thus protecting the matrix by preventing heat and oxygen transfer and reducing the concentration of combustible gas. NiNH4PO4·H2O is expected to serve as a new high-efficiency flame retardant for EP.
危险品化学品经营许可证（带存储）