Permanent P/N-rich polymeric coating capable of extinguishing flame on cotton fabrics

Although polyphosphazenes having attracted attention for use as flame-retardant coatings for textiles, nonetheless their add-on level is still far from ideal with regard to high-efficiency flame-retardant properties, wearing comfort and durability. Herein, for the first time, a cross-linkable phosphorus and nitrogen-rich polyphosphazene, poly(methoxy/allylphenoxy)phosphazene (PMAP), with mainly methoxy groups and an appropriate amount of unsaturated chemical bonds containing allylphenoxy side groups (ca. 8 %) was synthesized. Subsequently, the noncombustible, transparent, elastic crosslinked PMAP coating was coated on cotton fabrics through dipping and photoinduced cross-linking processes. The PMAP-coated cotton showed high-efficiency flame-retardant properties along with remarkably high durability. The intrinsic properties of cotton fabric, such as whiteness, gas permeability and bending rigidity, were highly reserved after being coated with PMAP. Interestingly, the flame-retardant properties of the 4.9 wt%-coated cotton increased, and the coated cotton obtained a self-extinguishing property and maintained >95 % of its initial mass after 60 rigorous laundry cycles. Moreover, the PMAP-coated cotton exhibited enhanced carbonization ability at lower temperatures, which was the key to the flame-retardant properties of cotton fabric. The PMAP-coated cotton also showed a lower peak heat release rate and total heat release values than the control cotton during combustion. Therefore, the comprehensive highly favorable properties of the PMAP coating make it a cutting-edge material for flame-retardant cotton fabrics and greatly expand its potential in practical applications.