Improved flame retardancy of cotton fabric by crosslinking 3-hydroxyphenyl phosphinyl propanoic acid using 1,2,3,4-butane tetracarboxylic acid.

Cotton fabric was treated with commercially available 3-hydroxyphenyl phosphinyl propanoic acid (3HPP) as a flame-retardant agent, in combination with 1,2,3,4-butanetetracarboxylic acid (BTCA) as a cross-linking agent and dicyandiamide (DCDA) as a catalyst for esterification. The phosphorus moiety successfully bonded with both the cotton fibres and the cross-linking agent, as confirmed by FTIR and XPS analyses. The concentration of 3HPP in the padding bath was varied from 1 % to 10 %. With optimization of 3HPP concentration and pH, the limiting oxygen index (LOI) of untreated cotton increased from 17.4 % to 29.5 %, and further improved to 31.5 % following atmospheric plasma treatment. Thermal degradation studies demonstrated a significant enhancement in stability: while virgin cotton exhibited approximately 80 % weight loss at 350 °C, treated samples showed only 40 % reduction at the same temperature. Cone calorimetry further indicated reductions in both the heat release rate and total heat release, along with delayed ignition. Additionally, the treatment showed good wash durability, with an LOI of 28.1 % retained even after 20 laundering cycles. This study addresses the key durability challenges of flame-retardant treatments for cotton fabrics and highlights the potential of this system for improving both safety and performance.