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Nylon can be flame retarded by halogen/antimony or other flame retardant synergistic systems, or by halogen-free flame retardant systems such as red phosphorus or melamine. From the quantitative point of view, halogen/antimony synergistic system is still the most widely used nylon flame retardant system. In some parts of Europe and Asia, efforts are being made to find alternatives to halogen flame retardants. Generally speaking, these alternative systems have some problems, such as low thermal stability or moisture absorption. For red phosphorus, there is a storage problem because it is inflammable. The following are the main flame retardants used in nylon and their respective advantages and disadvantages.

(1) Halogen-containing flame retardant system: one of the most important and widely used abroad is styrene bromide polymer, which has excellent thermal stability and good fluidity in processing because it is melt-mixable with nylon. In addition, the flame retardant nylon prepared by this method has excellent electrical and mechanical properties. The limitation of this flame retardant lies in its poor light stability and incompatibility with nylon. In addition, its cost is higher than that of Decabrominated diphenyl ether which is widely used in China. Another kind of flame retardant which has been used in nylon for many years is dimethyl flame retardant. It is a chlorine-containing flame retardant with high flame retardant efficiency and electrical properties, but its limitation in thermal stability makes it only suitable for nylon flame retardant system with lower processing temperature. At present, the most widely used flame retardant in China is decabromobiphenyl ether. Because of its high bromine content, it has high flame retardant efficiency for nylon and is the most economical flame retardant. However, because it is a filler flame retardant, it has a great negative impact on processing fluidity and physical and mechanical properties of products. In addition, its thermal stability and optical stability are also poor. In recent years, a new flame retardant used in nylon flame retardant is decabromodiphenoxyethane, which has the same bromine content and high flame retardant efficiency as Decabrominated diphenyl ether, and has the same problem as styrene bromide polymer (so-called dioxin). In addition, it has good thermal and optical stability. Its limitation is that it belongs to filler flame retardant like Decabrominated diphenyl ether and has poor compatibility with polymer, so its processing fluidity and physical and mechanical properties are poor. In addition, compared with Decabrominated diphenyl ether, the cost increases higher.

(2) Halogen-free flame retardant system: The halogen-free flame retardants widely used in nylon are red phosphorus and melamine salts. Red phosphorus has high flame retardant efficiency and can improve the arc resistance of products, but its storage and color limitations greatly limit its application in nylon, generally only in nylon 6. Another halogen-free flame retardant used in nylon is melamine salt, mainly melamine urate and phosphate. They have good flame retardant efficiency, but their thermal stability is poor, and their electrical properties are poor in humid environment because of their moisture absorption.