Nylon (PA, also known as polyamide) is the first resin developed by DuPont for fiber in the United States. It was industrialized in 1939. Since the 1950s, the amount of PA used has increased dramatically. Because nylon has good comprehensive properties, including mechanical properties, heat resistance, abrasion resistance, chemical resistance, and self-lubrication, and has a low coefficient of friction, it is easy to process. It is widely used in electronics, automobiles, construction, and office Equipment, machinery, aerospace and other industries, many of which have flame retardant requirements. With the gradual upgrading of environmental protection requirements, more and more applications require the use of halogen-free flame retardant PA. However, PA halogen-free flame retardant is more difficult. There are many problems with halogen-free flame retardants on the market. Double-cage silicone flame retardants are expected to solve the above problems and cause a revolution in nylon halogen-free flame retardants.

The halogen-free flame retardants currently used in PA are mainly diethylphosphinate series. Its decomposition temperature is greater than 350 ° C. It can be extruded at high temperature and high speed during the processing of PA engineering plastics, and the amount of application in the market is very large.
But there are some problems with diethylphosphinate:
1. Diethylphosphinate is a small molecule with very high polarity and poor dispersibility in PA processing, which has a certain effect on the mechanical properties of PA.
2. Diethylphosphinate is the "acid source" in flame retardants, which will decompose into acid sources such as phosphoric acid during the flame retardant process, catalyzing the nylon itself to become carbon, so as to achieve the flame retardant effect of heat insulation and oxygen barrier If you want to make PA have good flame retardancy, its added amount is relatively large, which will also affect the mechanical properties of PA to a certain extent.
3. Diethylphosphinate does not form carbon by itself, and it is slowly added to nylon to form carbon, which will affect the glow wire experiment and cause an open flame.
4. Diethylphosphinate is a salt and not resistant to corrosion.

Future development trend: double cage silicone flame retardant
One of the future development directions of PA halogen-free flame retardants is silicone flame retardants for the following reasons:
1. The C-Si bond energy in the double cage silicone flame retardant structure is large, so it has excellent high temperature resistance;
2. In the process of carbon formation, the two elements C and Si are easy to form covalent bonds because they are in the same group, and they have a tetrahedral structure, which will form a three-dimensional network dense carbon layer. The cage-like structure is a CC hexahedron structure, and it is easy to form a three-dimensional network-like dense carbon layer. It has good heat insulation and oxygen barrier effects, and therefore exhibits excellent flame retardancy.
3.Si element has lubricating effect in flame retardant molecules, making it easy to squeeze out during processing.