A facile surface phosphorylation grafting strategy to fabricate durable flame-retardant wool fabric

Inspired by the phosphorylation of amino acids, a facile surface grafting approach with dimethyl phosphate (DMP) was developed to endow durable flame retardancy to wool fabrics. The grafting behavior between DMP and wool fibers was investigated by ATR-FTIR analysis and XPS spectroscopy. After undergoing the grafting modification process, the flame-retardant ability of the grafted sample was clearly enhanced, with an increase in the limiting oxygen index (LOI) value from 23.8 % to 30.5 %. Even after 25 washing cycles, it still retained 27.0 %. Meanwhile, cone-calorimeter tests (CCT) demonstrated that the grafted wool fabric achieved a peak heat release rate that decreased by 28.1 % and total heat release decreased by 19.2 %. The grafted wool fabric also showed better thermal stability, with T50% increased from 370 C to 397 degree celsius (N-2 atmosphere), 408 C to 439 degree celsius (air atmosphere). Char residues had a large increase, from 0.6 % to 21.8 % (air atmosphere), during a thermogravimetric (TG) test. Moreover, char residue analysis confirmed that the introduced phosphorylated structure could assist the wool fabrics to form intensive, expanded protective char residue after exposure to flame, protecting the matrix from decomposition. In this work, we provide a facile strategy for fabricating durable flame-retardant (FR) wool fabrics under a low temperature.