Halogen/antimony or other flame retardant synergistic systems, halogen-free flame retardant systems based on red phosphorus or melamine. From a quantitative point of view, the halogen/antimony synergistic system is still the most widely used PA flame retardant system. In some parts of Europe and Asia, efforts are underway to find alternatives to halogenated flame retardants. However, these alternative systems are generally considered to have problems such as poor thermal stability and hygroscopicity. For red phosphorus, there are storage issues due to its flammability. The following are the main flame retardants used in nylon and their advantages and disadvantages.
1. Halogen-containing flame retardant system: A brominated styrene polymer with excellent thermal stability that is important and widely used abroad is being melt-mixed with PA. The process has good fluidity. In addition, the flame retardant PA prepared with it also has excellent electrical, physical and mechanical properties. The limitations of this flame retardant are its low photostability and incomplete compatibility with PA. It is also more expensive than decabromodiphenyl ether, which is widely used in China. Another flame retardant that has been used in PA for many years is flammable. This is a chlorine-containing flame retardant with high efficiency and electrical properties, but limited thermal stability. Only suitable for low processing temperature nylon flame retardant systems. Currently, the widely used flame retardant in China is decabromodiphenyl ether. Due to its high bromine content, PA has high flame retardant efficiency and is an economical flame retardant. However, since it is a filled flame retardant, it has a large detrimental effect on the flowability of processing and the physical and mechanical properties of the product. It also has poor thermal and light stability. In recent years, a new type of flame retardant for nylon flame retardants developed by people is decabromodiphenoxy ethylene oxide, which has the same bromine content as decabromodiphenyl ether and has a high flame retardant efficiency. . And unlike brominated styrene polymers, it has no DPO (so-called dioxin) problems. It also has excellent thermal and light stability. The limitation is that it is the same filler-type flame retardant as decabromodiphenyl ether, which has poor compatibility with polymers, resulting in poor processing fluidity and physical and mechanical properties of the product. In addition, the cost increase is significant compared to decabromodiphenyl ether.
2. Halogen-free flame retardant system: The widely used halogen-free flame retardants in PA are red phosphorus flame retardant and melamine salt. Red phosphorus has high flame retardancy and can improve arc resistance of products, but storage and color restrictions severely limit its use in PA, usually only in PA6. Another halogen-free flame retardant used in PA is melamine salts, mainly melamine urate and phosphate. Although it has good flame retardancy, it has low thermal stability and readily absorbs moisture, resulting in poor electrical performance in humid environment.
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