Phosphorus-doped organic–inorganic hybrid silicon coating for improving fire retardancy of polyacrylonitrile fabric

In this study, in order to increase the flame retardancy of polyacrylonitrile fiber fabric, an organic–inorganic hybrid silane coating doped with polyphosphoric acid was prepared using tetraethoxysilane as the precursor by sol–gel technique. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscope confirm the successful silicon and phosphorus-doped silicon coating on polyacrylonitrile fabric. Obviously, the char residue values at 800 °C of the silica-coated and phosphorus-doped silica coated polyacrylonitrile fabric samples were observed to increase 17.93 and 25.92%, respectively than that of the control sample. The peak and total heat releases of the phosphorus-doped silica coated polyacrylonitrile fabric significantly reduced to only 44.9 and 42.1% of that of polyacrylonitrile fabric, respectively. Besides, both the peak values of smoke production rate and total smoke production are remarkably reduced. The results show that the coated layer can effectively improve the thermal stability, and strengthen the ability to form a thermally stable and condensed barrier for heat and mass transfer. Furthermore, the phosphorus-doped silica-coated polyacrylonitrile fabric provided a novel and efficient method to prepare flame retardant polyacrylonitrile fabric with attractive features.

In this article, an efficient and facile method was successfully demonstrated to prepare novel fire retardant PAN fabric. The organic–inorganic hybrid silane coating doped with polyphosphoric acid (PPA) can effectively retard the thermal degradation of PAN fabric, enhane the char-forming ability and can produce a stable and compact shielding layer. The phosphorus-doped silica-coated PAN fabric has lower values of pHRR, THR, pSPR, TSP, aMLR and FIGRA, compared to the control PAN fabric.