Obtaining Polyacrylonitrile Carbon Nanofibers by Electrospinning for Their Application as Flame-Retardant Materials

The article describes obtaining polyacrylonitrile (PAN) nanofibers by electrospinning on a setup developed at the Mendeleev University of Chemical Technology of Russia (MUCTR). A technique for producing PAN-based carbon nanofibers (CNFs) and PAN-based CNFs modified with titanium oxide (TiO₂) is presented. The article presents a comprehensive study of the characteristics of PAN-based nanofibers and CNFs, including an analysis of the external structure of the fibers, the dependence of fiber diameters on the viscosity of the initial solutions, the effect of temperature treatment on the functional groups of PAN, elemental analysis, and flame-retardant properties. It was found that the fiber diameter and its external structure strongly depend on the viscosity of the initial solutions; an increase in viscosity leads to a linear increase in the fiber diameter. Preliminary temperature treatment at 250 °C helps stabilize PAN nanofibers and prevents their melting at the carbonization stage. The differential scanning calorimetry results allowed us to determine the presence of peaks for the initial PAN nanofibers, indicating an exothermic process in the temperature range of 290-320 °C. The peak height decreased with increasing TiO₂ concentration in the samples. For CNF samples of different compositions, the endothermic effect prevailed in the temperature range of 400-700 °C, indicating the possible flame-retardant properties of these materials. The limiting oxygen index (LOI) was calculated based on the thermogravimetric analysis results. The highest LOI values were obtained for CNFs based on PAN without adding TiO₂ nanoparticles and CNFs modified with TiO₂ (3 wt.%). The resulting CNF-based nonwovens can be recommended for use in heat-protective clothing, flame-retardant mattresses, and flame-retardant suits for the military.