Abstract 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.
Polysulfide-based aqueous redox flow batteries (PS-ARFBs) are a viable alternative for energy storage owing to their impressive theoretical capacity, inherent safety features, low operating costs, and cost-effective design. However, the primary challenges facing PS-ARFBs are slow kinetics and limited cycle life, which significantly impede their practical applications. To overcome these obstacles, we have developed an innovative functional electrode (KB/S-HCN-2:1-CF) that integrates S8/S x 2- redox pairs (KB/S) with hydrophilic carbon nanocuboids (HCNs) as electrocatalysts. This design enhances the redox kinetics of polysulfides and optimizes sulfur utilization. Remarkably, the KB/S-HCN-2:1-CF electrode reduces the overpotential of a polysulfide-ferri/ferrocyanide (S-Fe) redox flow battery from 1110 to 237 mV at a current density of 40 mA cm-2. Furthermore, an S-Fe flow cell equipped with this modified electrode demonstrates an increased initial capacity of 268.9 mAh at 40 mA cm-2 at a lower S x 2- concentration and an improved energy efficiency of nearly 10%. Particularly, a plausible explanation for the roles of S8 and HCNs in promoting the reduction of polysulfides has been proposed, as confirmed by DFT methods and ex-situ UV-vis spectroscopy in polysulfide electrolytes. This study offers a promising approach to the challenges faced by PS-ARFBs, paving the way for high-capacity and long-lasting performance.
