Cyano amidoximation and catechol functionalization of waste polyacrylonitrile for fabricating flame retardant, thermal insulation and smoke suppression aerogels

Waste PAN was recycled into flame retardant aerogels to realize utilization. • The aerogels were free of flame retardant elements such as P, Cl and Br. • The aerogels exhibited ignition resistance and thermal insulation properties. • Amidoxime self-crosslinking flame retardant mechanism was proposed. To achieve the reuse of polymer material waste, polyacrylonitrile (PAN)-based flame-retardant aerogels (PAN@HA-aer, PAN@HA@PCA-aer) were prepared using waste PAN fiber as raw materials. The cyano groups of PAN were modified via amidoximation with hydroxylamine hydrochloride and functionalized by 3,4-dihydroxybenzaldehyde. The test results indicated that the self-crosslinking effect of amidoxime groups, the aromatic carbonization promotion of catechol, combined with the physical barrier effect of the porous skeleton, synergistically improved the flame retardancy and thermal insulation performance of PAN@HA-aer and PAN@HA@PCA-aer. Combustion tests showed that compared with PAN-aer, the total heat release (THR), peak heat release rate (PHRR), smoke production rate (SPR), and the generation of toxic gas HCN of PAN@HA-aer and PAN@HA@PCA-aer were all significantly reduced. Moreover, the limiting oxygen index (LOI) was increased to over 46%, demonstrating excellent flame-retardant and smoke-suppressant properties. This work not only developed eco-friendly flame-retardant porous materials, but also provided a promising strategy for high-value recycling and resource utilization of waste PAN fiber. Download: Download high-res image (226KB) Download: Download full-size image