Enhancement of Flame Resistance of Cotton Fabrics Using Multilayer Biomaterial Coatings of Chitosan and Sodium Alginate

Cotton fabrics are widely used in textiles due to their comfort and breathability, but their high flammability (limiting oxygen index (LOI) ≤ 18%) poses serious safety risks. While conventional flame-retardant treatments often rely on synthetic chemicals or toxic additives, biobased alternatives remain underdeveloped. The flame resistance of cotton fabrics may be enhanced using multilayer biocoatings of chitosan and sodium alginate applied via layer-by-layer (LBL) assembly—a sustainable and scalable approach. Cotton samples were coated with chitosan and sodium alginate bilayers (1, 2, 5, and 10 layers) using the LBL method. Flame resistance was evaluated using vertical flame tests and limiting oxygen index (LOI) testing according to ASTM D2863-09. The sample coated with 10 bilayers significantly outperformed uncoated cotton and lower-layer samples. With a char length of 9.72 cm (68% reduction), no dripping was observed in the vertical flame tests, and the LOI value was 23.47% compared to uncoated cotton (LOI = 18.04%). These improvements were attributed to the formation of a cohesive and protective carbon layer, which is likely capable of inhibiting the formation of flammable gases. Biomaterial multilayer coatings made from biomaterials, such as chitosan and sodium alginate, represent a promising and environmentally friendly alternative to traditional methods in improving cotton’s flame resistance. The development of this technology points to potential applications in protective textiles and industrial safety clothing. Notably, chitosan and sodium alginate coatings are biocompatible. The term “biomaterials” refers to materials intended for interaction with biological systems, particularly for biomedical-related applications. The term “biobased materials” is used exclusively to describe materials derived from renewable biological sources.