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 (<100 nm). Thermal analysis revealed enhanced stability and char-forming ability at 800 °C, with a 75% increase in the Limiting Oxygen Index (LOI). The CP 10 sample showed superior flame retardancy, with reduced self-ignition time (23 s), and higher LOI (32%) and char yield (88%) compared to CP 0 . The optimized FR-NC demonstrates strong potential as a sustainable reinforcement material for composites, electronics, and packaging applications. • Extracted pure cellulose from waste cotton and converted it into nanocrystal form. • Nanocrystal was modified through a highly concentrated alkali solution and phosphorylated with different ratios of phosphorus-containing compounds. • Optimize the performance of flame retardants and use them as fillers or reinforcements in structural composites, electronic items, floor coatings, and food packaging materials.
Islam et al. (Tue,) studied this question.