Flame Resistance Meets Green Chemistry: Ionic Liquids as Next-Generation Agents for Textile Functionalization

This study focuses on the development of eco-friendly flame-retardant coatings for polyester-cotton fabrics using two ionic liquids—[A, PF₆] and [Py, PF₆]—incorporated into a polyacrylic acid (PA) matrix through the knife-coating method. The process was optimized using a Box–Behnken experimental design to evaluate the influence of ionic liquid concentration and coating thickness on flame-retardant performance. Results from vertical flame tests showed a substantial increase in flame resistance, particularly for fabrics treated with PA + [Py, PF₆], which exhibited no ignition after 20 seconds of flame exposure. Surface morphology observed through SEM revealed smoother and more cohesive coatings in samples containing [Py, PF₆], attributed to its aromatic and polar structure enhancing fiber interaction. Drop tests confirmed improved water repellency, while tensile strength measurements demonstrated that the coatings maintained or improved the mechanical properties of the fabric. Additionally, washing durability tests showed that both flame-retardant and hydrophobic properties were partially retained after five laundering cycles. Overall, this work highlights the potential of ionic liquids as effective, sustainable flame-retardant agents for textile applications.