Amino acid-based flame retardants for textiles: Recent advances in properties and synthesis methods: A review

Textiles, both natural and synthetic, are essential in clothing and industrial applications but are inherently flammable, requiring effective flame-retardant (FR) treatments. Conventional FRs, particularly halogen- and phosphorus-based systems, raise concerns regarding health and environmental impacts. Amino acids, available from natural sources or industrial byproducts, represent a sustainable alternative due to their renewability, biodegradability, and chemical versatility. This review provides a comprehensive assessment of amino acid-based FRs for textiles, integrating studies published between 2010 and 2025. It examines synthesis strategies such as phosphorylation, Mannich reactions, and polyamidoamine formation; evaluates application methods across substrates including cotton, polyester, and Lyocell; and analyzes fire performance using metrics such as Limiting Oxygen Index, Peak Heat Release Rate, and Total Heat Release. Environmental and economic considerations, mechanisms of action, and durability of treatments are also discussed. By consolidating quantitative performance data and classifying approaches, this work addresses gaps in previous reviews and highlights opportunities for further development of amino acid-based FRs as promising candidates for safer, sustainable protection in textiles used in clothing, automotive, and filtration applications.