Synthesis of a cytosine-derived phosphorus‑nitrogen flame retardant and its application in cotton fabrics

The growing awareness of public safety has spurred significant interest and research in flame-retardant cotton fabrics. The present study aimed to design a phosphorus‑nitrogen-based flame retardant derived from cytosine and apply it to cotton fabrics through a dipping-padding-baking-washing process. The resulting cotton fabrics (Cotton/CyP) exhibited exceptional fire resistance and self-extinguishing properties. Specifically, the LOI value reached 35.3 %, and the char residue length was 74 mm after vertical burning tests, although washable durability was limited. Compared to pure cotton, Cotton/CyP10 showed a 63.4 % reduction in the peak of heat release rate value and a 29.2 % decrease in total heat release. In conjunction with the thermal stability and decomposition products analysis, as well as char residues evaluations, these results indicated that Cotton/CyP primarily functioned by promoting the formation of a dense, regular and graphitized char layer during combustion predominantly in condensed phase. This research developed fabric holds great promise for practical applications, significantly enhancing fire safety with high efficiency.