Flame Retardant Performance and Principle of Nylon PA6 Composite

Jan. 01, 70

1. Flame retardant properties of nylon PA6 composite

As the preparation technology becomes more mature, PA6 has become a popular polymer material in many fields such as electrical and electronics, automobiles, and communications. In particular, PA6 composite materials have more diverse structures and functional parts.

When applied in these fields, PA6 composite materials often face extreme working conditions such as high temperature, flammability, leakage, and short circuit. Among them, flammability has become one of the important indicators of whether PA6 composite materials can work safely and normally.

The flame retardant grade of unmodified PA6 itself can reach UL94 V-2 grade, and the limiting oxygen index is between 20-22%. This means that when exposed to an open flame, PA6 will burn quickly, and at the same time, there will be a low level, causing the open flame to spread.

The PA6 composite material makes this indicator more complicated: some composite components will help PA6 burn, for example, the common glass fiber will make the material burn faster because of the candle wick effect.

As we all know, the industry has very strict flame-retardant requirements for the materials used in automobiles, electrical appliances and other products. Therefore, PA6, which has both good flame retardancy and mechanical properties, is of great research and commercial value. Especially in today's high price of PA66, the potential of high flame retardant PA6 composites is very large.

266-改性PA66（黑色粒子）

2. The flame retardant principle of nylon PA6

To put out the fire, the most important thing is to know how the fire started. Combustion is generally divided into three forms: evaporative combustion, thermal decomposition combustion, and solid surface combustion. PA6 and most polymer materials are all thermal decomposition combustion methods.

The main combustion process of nylon PA6 is as follows:

(1) First, the material is heated up. When the overall temperature of the material rises to about 200°C, the material will melt and soften significantly, and the polymer molecules on the surface of the material will begin to undergo thermal oxidation and decomposition;

(2) When the temperature rises further, the thermal oxidative decomposition reaction will be more sufficient, and a large number of free radicals will be generated. These free radicals will combine with the methylene group in the molecular structure of PA6 to accelerate the decomposition;

(3) The large number of polar bonds in PA6 make this material have strong water absorption. Under high temperature, the hydrolysis of amide bonds will also occur simultaneously. The final product of hydrolysis is carbon-containing small molecular combustibles, mainly internal Amide and cyclopentanone, etc.;

(4) These small-molecule combustibles are fully mixed with oxygen under the action of high-temperature diffusion and convection, and finally ignite. The heat generated in this process will not only be released to the outside world, but also act on the PA6 itself, that is to say, even if the external heat source is removed, the combustion process will continue.