Synergistic chitosan-phospholipid bilayer coatings via layer-by-layer assembly for multifunctional flame-retardant...

The development of sustainable flame-retardant textiles with multifunctional performance remains a significant challenge due to the environmental concerns associated with conventional chemical treatments. In this study, a bio-based bilayer coating system composed of chitosan (CS) and phospholipids (PL) was fabricated on cotton fabrics via a layer-by-layer (LbL) assembly technique. The synergistic interaction between nitrogen-rich chitosan and phosphorus-containing phospholipids enabled the formation of an efficient protective char layer during combustion. The treated fabrics exhibited a substantial increase in limiting oxygen index (LOI) from 18% to 33%, achieved a UL-94 V-0 flame-retardancy rating, and reduced flaming time from 30 s to complete self-extinguishing behavior after five bilayers. Furthermore, the char length decreased from 35 to 8 mm, while carbon monoxide emissions were reduced from 328 to 253 ppm, confirming effective suppression of combustion. Thermogravimetric analysis confirmed enhanced thermal stability and higher char residue. In addition to fire resistance, the modified textiles demonstrated excellent antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as remarkable UV protection and increased surface hydrophobicity. Toxic gas analysis revealed a notable decrease in harmful emissions during combustion. This study presents the systematic integration of chitosan-phospholipid bilayers for achieving simultaneous flame retardancy and multifunctionality in cotton textiles using an eco-friendly approach. These findings provide a promising strategy for the design of advanced sustainable protective fabrics.