Fire Retardant Treatments for Polyamide 6 and 66: Advances and Trends over the Last Five Years

As pivotal engineering materials in the plastics and textile industries, polyamide 6 (PA6) and polyamide 66 (PA66) require breakthroughs in flame retardancy to unlock or expand their potential applications. This review systematically summarizes the research progress of flame retardant (FR) PA6 and PA66 over the past five years, providing a multidimensional analysis centered on two critical application domains: FR textiles and FR composites. In the domain of PA6 and PA66 FR textiles, this review highlights industry progress in the development of ecofriendly FR coating technologies, enhancement in laundering durability, optimization of wear comfort, and integration of multifunctional designs. The focus for composite materials shifts to innovative strategies involving halogen-free and intrinsic FR formulations alongside approaches to enhance mechanical performance and achieve functional synergies. This review further elucidates the key challenges faced in the industrialization of FR PA6 and PA66. Beyond refining the laundering–wear performance of textiles and the mechanical robustness of composites, emphasis should be placed on dual-integration strategies, such as harmonizing flame retardancy with environmental sustainability and multifunctionality. These insights establish a theoretical framework to guide the engineering deployment of FR PA6/PA66 in specialized high-performance fields.