Research progress in halogen-free flame-retardant nylon 6 fiber

Nylon 6 fiber was among the first synthetic fibers to be industrialized and is widely utilized across textiles, automotive, construction, and electronics due to its excellent mechanical and chemical properties. However, its inherent flammability and tendency to drip when melted limit its application in fire-sensitive environments. In response, significant efforts have been made to improve its flame-retardant performance. This review focuses on recent advances in halogen-free flame-retardant strategies specifically developed for Nylon 6 fibers. Flame retardants based on phosphorus, nitrogen, and nanoscale materials have been incorporated into the polymer matrix through methods such as blending, in situ polymerization, and copolymerization. These modifications aim to enhance flame retardancy by increasing the limiting oxygen index, reducing heat release, and improving thermal stability, while maintaining mechanical strength and spinnability. Despite substantial progress, challenges remain, including the toxicity of combustion byproducts, limited environmental compatibility of some additives, and negative effects on processing performance. This review emphasizes the structure–property–performance relationships that govern flame-retardant efficiency and highlights multifunctional designs offering improved processability, thermal protection, and environmental safety. By critically evaluating current materials and methods, the review provides technical insight into the development of high-efficiency, halogen-free flame-retardant systems for Nylon 6 fibers and outlines potential directions for future research.