Construction of durable eco-friendly biomass-based flame-retardant coating for cotton fabrics

Inspired by the classic dye-fixing process, a novel eco-friendly biomass-based coating that neither used traditional elements such as Cl, Br, P nor toxic organic solvents was first developed to endow cotton fabrics with durable flame retardancy from biomass tannin (TA), tartar emetic (TE), and Fe2+. In this coating system, TA used as a charring agent was fixed onto the fiber surface of cotton fabric by TE in water via the action like dyestuff fixing, while Fe2+ coordinated with the hydroxyl of TATE can catalyze TA and cotton fibers to form graphited stable carbon residues for achieving high flame retardance. Consequently, the resultant fabrics showed great flame retardance with excellent durability. Even after 100 laundering or friction cycles, their limiting oxygen index values of ~27.0% hardly changed. And the washed flame-retardant cotton fabrics still easily passed the horizontal flammability test with an extremely low destroy spread speed. Moreover, scanning electron microscopy, confocal laser scanning microscope, and cone calorimeter test results all confirmed the durability of the coating. The flame-retardant mechanism analysis demonstrated that the coating could promote the cotton fibers to form dense and regular graphitized carbon layers and effectively protect the matrix from decomposing to flammable gases under high temperatures. In addition to durable flame retardancy, the mechanical properties and hydrophilicity of cotton were slightly influenced by the flame-retardant coating. This eco-friendly biomass-based flame-retardant coating provides a new strategy for fabricating green flame-retardant systems without using hazardous compounds.