Cellulose-Based Flame-Retardant Materials: Mechanisms, Evaluation, and Design Strategies

Cellulose-based materials are promising sustainable alternatives to petroleum-derived polymers because of their renewability, biodegradability, and structural versatility; however, their inherent flammability significantly limits their applications in fire-sensitive areas. This review presents a systematic overview of recent advances in flame-retardant cellulose-based materials, focusing on combustion fundamentals, fire-performance evaluation, and flame-retardant design strategies. The thermal decomposition behavior of cellulose is first discussed, emphasizing the competition between volatile generation and condensed-phase char formation that governs flammability. Common fire-performance evaluation methods, including thermogravimetric analysis, limiting oxygen index, vertical burning tests, and cone calorimetry, are then examined in the context of flame-retardant mechanisms. Subsequently, major preparation approaches─physical blending, surface coating, chemical modification, and grafting copolymerization─are comparatively reviewed. Representative phosphorus-, nitrogen-, boron-, silicon-, and metal-based systems are highlighted to illustrate condensed-phase, gas-phase, and synergistic flame-retardant effects. Finally, current challenges and future opportunities are discussed, focusing on durability, multifunctionality, mechanistic understanding, and scalable manufacturing. By integrating fundamental combustion principles with material design strategies, this review provides a framework for the rational development of sustainable, halogen-free, flame-retardant cellulose materials.