Preparation, flame retardancy and thermal degradation behaviors of polyacrylonitrile fibers modified with diethylenetriamine and zinc ions

A kind of flame-retardant polyacrylonitrile fiber was prepared successfully by the modification with diethylenetriamine and zinc ions (Zn²⁺). The chemical, aggregation and morphological structures of the aminated fibers were studied by Fourier transform infrared (FTIR) spectra, X-ray diffraction and scanning electron microscope (SEM). Meanwhile, mechanical and adsorption properties were investigated by a tensile tester and atomic absorption spectrometry. The flame retardancy of the modified fibers was significantly improved after modification. And the thermal degradation behaviors and flame retardancy mechanisms were studied in detail. The microscale combustion calorimeter and TG-FTIR results showed that the modified fibers decomposed less combustible gases and more non-combustible gases comparing the original fibers. And thermogravimetric analysis and SEM tests revealed that Zn²⁺ would stabilize the main chains and promote formation of compact char layers. And differential scanning calorimetry tests indicated that Zn²⁺ would inhibit the cyclization exothermic process. Results showed that the combination of gas phase and condensed phase mechanisms optimized the flame retardancy performance.