关键词: 聚丙烯腈, 阻燃, 层层自组装, 植酸, 电缆材料, 3-氨丙基三乙氧基硅烷

Abstract:

Objective Polyacrylonitrile (PAN), is widely used in high-value-added applications, particularly in the development of domestically produced PAN filaments for the shielding covering layer of cable core materials. Cables are predominantly installed in buildings and densely populated areas, making them vulnerable to fire caused by factors such as increased loads, wire short-circuiting, and other electrical faults. During combustion, toxic gases, including hydrogen cyanide (HCN) and carbon monoxide (CO), are released, posing significant risks to human life and property safety. Consequently, enhancing the flame retardant properties of PAN filament fabrics has become a critical research focus in the industry.

Method In order to obtain the environmentally friendly flame retardancy of PAN fabrics, flame retardant polyacrylonitrile filament fabrics were prepared by using PAN filament fabrics as the substrate and constructing on it a ternary self-assembled flame retardant system using phytic acid (PA)/polyethyleneimine (PEI)/3-aminopropyltriethoxysilane (APTES), adopting the layer-by-layer self-assembly method. The surface morphology and macromolecular structure of the flame retardant modified fabrics, as well as their thermal stability and flame retardant properties were investigated.

Results The results showed that after self-assembly of PA/PEI/APTES layers, the flame retardant elements such as phosphorus (P), nitrogen (N) and silicon (Si) were effectively introduced on the surface of the PAN fabric, whereas the untreated PAN fabric had only the presence of C, N and O elements on its surface. The new P element was added on the surface of PAN-PEI fabrics, and the P content was increased to 8.81%, and the H₂PO₄/PO₄ characteristic peaks at 133.8 eV were observed after self-assembly. The characteristic signal of Si element appeared in the XPS spectra when increasing APTES from 1.0% to 3.0%. The characteristic peak of H₂PO₄/PO₄ was also observed. After further introduction of APTES, the Si element was increased from 1.13% to 3.78% when increasing APTES concentration from 1.0% to 3.0%, while the N and P elements were slightly decreased. The residual carbon of the fabrics before and after flame-retardant modification increased from 0 to 13.1% at 900 ℃, the limiting oxygen index (LOI) of the fabrics increased from 17.4% to 27.5%, the sustained ignition and negative ignition time of the fabrics reached 0 s. The total smoke release was decreased by 63.6% from 1.1 to 0.4 m², and the heat release rate was reduced by 18.9%. The fabrics exhibited excellent performance after PA/PEI/APTES alternating assembly.

Conclusion A ternary flame retardant system of PA/PEI/APTES was constructed using layer-by-layer self-assembly technology, and the flame retardant polyacrylonitrile filament fabrics were successfully prepared, which is expected to be applied to shielding wrapping layers of internal cores of cables as well as to some application environments that do not need to be washed. Compared with the untreated PAN fabrics, the self-assembled flame retardant modified fabrics showed an increase in LOI value from 17.4% to 27.5%, a decrease in the maximum value of heat release rate by 18.9%, and a decrease in the total smoke release by 63.6%, which demonstrated that the flame retardant and smoke inhibition properties of the flame retardant modified fabrics were greatly improved.

Key words: polyacrylonitrile, flame retardant, layer-by-layer self-assembly, phytate, cable material, 3-aminopropyltriethoxysilane