Green P–N coating by mechanochemistry: efficient flame retardant for cotton fabric

Cotton fabric is widely used on many occasions, but it is flammable with high fire risk. To meet the great fire safety demands of cotton fabric, a novel Lignocellulosic-based P–N synergistic (LFPN) flame-retardant coating with high efficiency and environment friendly was developed via mechanochemistry strategy in the aqueous phase. The characterisation results showed the stable P–O–C bond formed to bind both lignocellulosic fibre and Ammonium polyphosphate (APP). Meanwhile, LFPN has an excellent dispersion in water with a nanometer-scale enveloping rod structure. The cotton fabric treated by the LFPN coating showed outstanding flame-retardant properties, the Peak heat release rate (PHRR) was reduced by 84.4%, and the Limiting oxygen index (LOI) value was increased by 150.7% compared with control cotton fabric. Moreover, there was a self-extinction phenomenon during the Vertical flammability test (VFT) of flame retardant cotton. Based on the analysis of the combustion and pyrolysis process, a gas-condensed two-phase flame retardant mechanism model was proposed, which could explain the action process of LFPN for cotton fabric during combustion. Graphical abstract