Durable and high-efficiency casein-derived phosphorus-nitrogen-rich flame retardants for cotton fabrics

A casein derivative (CADP) was synthesized using casein, which is bifunctional containing both –P=O(O − NH 4 + ) 2 reactive groups and –P(=O)–O–C– groups, and the durable flame-retardant cotton fabrics were successfully prepared by CADP. The –P=O(O − NH 4 + ) 2 reactive groups allowed CADP to be firmly grafted onto cellulose. The –P(=O)–O–C– groups made flame-retardant cotton fabrics more resistant to soaping and improved its durability. The modification by 40% CADP increased the limited oxygen index value of cotton fabric from 17.4 to 41.6%, which maintained at 26.4% after 50 cycles of home machine washes. The results of TG, TG-FTIR, FTIR and SEM indicated that CADP increased the condensed components and decreased the flammable gaseous compounds, resulting the positive effect on char formation of cellulose. The whiteness, softness and tensile strength of cotton fabrics were retained well after modification, and the treated cotton fabrics didn’t have skin irritation. Graphical abstract