Synthesis, modification, and performance optimization of flame-retardant nanocellulose from waste cotton

Growing interest in renewable materials and sustainable processes has positioned cellulose nanocrystals (CNCs) as a key bio-based material due to their low density, high mechanical strength, thermal stability, and biodegradability, though their inherent flammability remains a limitation. In this study, waste cotton (WC) was used to produce CNCs, which were subsequently chemically modified and phosphorylated to develop flame-retardant nanocellulose (FR-NC). Structural and chemical analyses (FTIR, XPS, elemental analysis, and zeta potential) confirmed successful chemical modification and phosphorus incorporation, which influenced crystallinity and increased nanofiber diameter while retaining the cellulose I structure. The CNCs exhibited high zeta potential (>30 mV) and nanoscale diameters (