Highly flame retardant of cotton fabric with a sandwich-like CoMnAl-LDH/bio-waterborne polyurethane/phytic acid nanocoating.

Eco-friendly and highly flame-retardant coatings for cotton fabrics urgently need to develop, but still faces significant challenges including the inadequacy of organic flame retardants, the adverse effects of high-load inorganic flame retardants on cotton fabrics, and the flammability of adhesives. Hence, this study describes a sandwich-like nanocoating for the fabrication of highly flame-retardant cotton fabric. Phytic acid (PA), a bio-based polyacid, was employed to prepare phosphorus-containing waterborne polyurethane (P-WPU) as the flame-retardant adhesive. With the help of multi-metallic layered double hydroxide (CoMnAl-LDH) and PA, six types of sandwich-like nanocoatings were constructed on cotton fabrics. Evaluation of their flame retardancy through vertical burning and cone calorimeter tests revealed that the sandwich-like nanocoating composed of PA as the top layer, P-WPU as the middle layer, and LDH as the bottom layer demonstrated exceptional flame retardancy in cotton fabric. It self-extinguishes within 5 s and the highest LOI value of 31.5% in all fabric samples, representing an increase of 89.76% over the pristine fabric. Meanwhile, the peak heat release rate (PHRR, 82.60 kW/m²) and total heat release (THR, 1.67 MJ/m²) were significantly reduced by 71.65% and 54.74%, respectively, relative to those of the pristine fabric. A synergistic flame-retardant mechanism was proposed that involved multiple barrier effects, catalyzing carbonization, and the release of non-flammable gases. Overall, this work may provide valuable insights for constructing highly flame-retardant cotton fabric, offering potential solutions to solve industry challenges. [ABSTRACT FROM AUTHOR]