Eco-friendly and efficient flame-retardant cotton fabric based on a multi-hydroxyl hyperbranched phosphoramidate

A kind of multi-hydroxyl containing hyperbranched phosphoramidate (HPAE) was successfully synthesized and characterized by FT-IR, 1H-NMR, 31P-NMR, and GPC. With the crosslinking of butane tetracarboxylic acid (BTCA), the flame-retardant cotton fabrics were prepared, and the combustion behavior and thermal degradation properties were investigated by limiting oxygen index (LOI), vertical flammability test, cone calorimetry test and thermogravimetric analysis. After treating with 300 g/L HPAE, good flame retardancy was obtained with LOI value of 29.0% and treated cotton fabrics can pass the vertical flammability test without afterflame and afterglow. The peak heat release rate was decreased from 255 to 93 kW/m2 and the total heat release after treatment was reduced by 37%. The thermal stability was greatly improved and over 40% of char residues maintained at 800 °C in N2. The washing durability of HPAE-BTCA treated cotton fabrics was also investigated and LOI value decreased from 29.0 to 25.2% after 25 washing cycles. Besides, the tensile strength, wrinkle recovery angle, and whiteness of cotton fabric after treatment were examined. Overall, our research provides a facile and effective approach to prepare durable flame-retardant cotton fabric, which has great potential in friendly flame-retardant textiles.