Functionalization of cotton fabrics through PEI/PA/FeAl ternary system with enhanced flame retardance and antibacterial properties

Cotton fabrics are widely used in clothing, packaging, and medical applications because of their excellent comfort, breathability, and low cost. However, it poses a threat to use them in specific scenarios, where flame retardance and antibacterial activity are highly desired. In this work, we propose the functionalization route by using layer-by-layer assembly of polyethyleneimine (PEI), phytic acid (PA), iron (Fe³⁺), and aluminum (Al³⁺) ions on cotton fabrics. Interestingly, the modified cotton fabric showed good biocompatibility in the cell viability (> 70%) and hemolysis (< 3%) test. In addition to biocompatibility, the antibacterial performance was largely improved for the modified cotton fabric with the antibacterial efficacy of > 99% due to the presence of Fe³⁺ and Al³⁺ that work in a synergistic manner. In term of flame retardance, the modified cotton fabric exhibited self-extinguishing characteristics in vertical burning experiments, with the Limiting Oxygen Index (LOI) of 35.0%. The excellent flame-retardant property was further supported by the results in cone calorimetry test, thermal gravimetric analysis, and TG-IR test, elucidating the underlying mechanism that rapid formation of dense char layer by the thermal decomposition of PEI/PA/FeAl system is effective to prevent the spreading of flame and thus protect the cotton from burning. This work provides a strategy to achieve multifunctionality on cotton fabrics, which may inspire the design on other types of fabrics or materials for extended applications.