The fire retardant properties and pyrolysis mechanism of polysulfonamide (PSA) fibers

Abstract

In the present work, the fire retardant properties and pyrolysis mechanism of polysulfonamide (PSA) fibers were investigated by cone calorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and pyrolysis-gas chromatography-mass spectrometry. The fire retardant behaviors were reflected by the cone calorimeter data under heat fluxes of 35, 50, and 75 kW/m2. This demonstrated that, when exposed to higher heat flux, PSA fibers were ignited easier and burned more completely, indicated by lower time to ignition and higher peak heat release rate. It was further confirmed from the morphology of the residual chars that the original fiber shape can be kept at lower heat flux, but it changed into coherent carbonaceous chars with holes at higher heat flux. In comparison of the FTIR spectra of raw fibers with residual chars, it was noticed that upon heating, the amide linkage was more liable to be broken than that of sulfone groups. Additionally, with elevated heat flux, most of the absorption bands vanished and transformed into the typical feature of carbonaceous material. The pyrolysis products showed that some volatile products with small molecular weight, such as benzene, benzonitrile, and aniline, can be created at high temperature, which can be easily ignited. With this research, the fire retardant properties of PSA fibers are revealed and the corresponding pyrolysis mechanism is proposed, which can guide its application in practice.