Biobased coating derived from fish scale protein and phytic acid for flame-retardant cotton fabrics

The nitrogen-phosphorus flame-retardant coating was formed on the surface of cotton fabrics via strong electrostatic attraction and hydrogen bonds with layer-by-layer coating of protein extracted from fishery waste fish scales and phytic acid (PA) derived from plant seeds. The flame retardant property of the coated cotton fabrics demonstrated a significant improvement with a limiting oxygen index of 31.1%, meeting the flame retardant requirements of commercial fire-protection suit. Especially, noteworthy, due to the synergistic smoke suppression effect of fish scale protein and phytic acid, the total smoke emission was greatly reduced by 139%. Meanwhile, the charring of the cotton fabrics treated with FSP and PA was significantly enhanced. Scanning electron microscopy and Raman results of the residual char further reveal that the treatment of the combined coating facilitates the formation of dense and regular graphitized char residue during combustion or under high temperature. This waste-sourced, biomass-derived coating paves a new way towards sustainable flame-retardant fabrics and has great significance in civil, military, and industrial fields.