Application And Research Trends of Flame Retardant Nylon Materials

Application And Research Trends of Flame Retardant Nylon Materials

Nylon (PA) is a thermoplastic engineering plastic containing amide bonds (-NHCO-) in the main chain of the molecule. Since the U.S. DuPont launched in 1930 to the present, PA because of its heat resistance, abrasion resistance, chemical resistance and self-lubricating and other advantages, in the automotive industry, electrical and electronic appliances, synthetic fibers, construction and other fields have a wide range of applications, and has become one of the world's largest production, the widest range of applications of engineering plastics.

Nylon material itself has certain flame retardant properties (different types of nylon oxygen index is different, of which PA66 oxygen index is 24. 3%, PA1010 oxygen index is 25. 5%, PA6 oxygen index is 26. 4%), but like home appliances, electronic appliances, new energy and other high requirements for flame retardant performance of the material industry, the flame retardant properties of the nylon itself can not meet the existing requirements for the use of the nylon, especially when the Especially when the glass fiber reinforced nylon material is used in these fields, the glass fiber filling makes the material easier to burn. Therefore, it is necessary to carry out an in-depth study on the improvement of flame retardant properties of nylon.

1. The development history of flame retardant nylon

Flame-retardant nylon materials made their debut in the middle of the last century, when they mainly relied on halogen-containing flame retardants to achieve flame-retardant properties.

Although the halogen-containing flame retardant system widely used in the early stage has a good flame retardant effect by adding only a small amount of flame retardant, the halogen-containing flame retardant will be decomposed and produce dioxin and other toxic gases that are harmful to the environment in the process of combustion. Therefore, while continuing to research new flame retardant technologies, halogen-free flame retardant has become the mainstream trend of research.

In this context, halogen-free flame retardants such as phosphorus-based (e.g., red phosphorus, ammonium polyphosphate, etc.), nitrogen-based (e.g., melamine and its derivatives), and silicone-based (e.g., siloxanes) have gradually emerged. These halogen-free flame retardants effectively enhance the flame retardancy of nylon materials while significantly reducing the potential hazards to the environment and human body.

In recent years, the booming development of nanotechnology has brought new breakthroughs for flame retardant nylon materials. Nanomaterials such as nano-montmorillonite, nanosilica, etc. can significantly improve the flame retardant properties of nylon materials with a very small amount of addition by virtue of their unique nano effect.

2. Flame retardant nylon flame retardant principle

There are many principles behind the flame retardant effect of flame retardant nylon materials.

First of all, it is the heat absorption and cooling effect, the flame retardant decomposes when it is heated and absorbs a large amount of heat, so that the surface temperature of the nylon material decreases, thus slowing down the combustion process. For example, ammonium polyphosphate will absorb a large amount of heat energy during thermal decomposition.

Secondly, it is the covering and isolation mechanism, the flame retardant will form a layer of dense covering layer when burning, which will isolate the nylon material from oxygen, effectively preventing the continuation of combustion. Through the termination of free radical reaction, flame retardants can capture and neutralize the free radicals generated during the combustion process, interrupting the chain reaction of combustion to achieve the purpose of flame retardant.

Finally, the principle of dilution of combustible gases also plays a role. The non-combustible gases generated by the decomposition of flame retardants, such as nitrogen, carbon dioxide, etc., can dilute the combustible gases generated by the combustion of nylon materials and reduce the intensity of combustion.

3. Main application fields of flame retardant nylon

Electrical engineering: low voltage switches and housings, series terminals, power supply and distribution systems, cable ducts and fasteners, contacts and power switches, coils, circuit breakers, etc.

Electronic products: power plugs, electrical and mechanical parts of EDP equipment and communication equipment, capacitor shells, chip carriers, etc.

Home appliances: washing machines, dishwashers, coffee makers, electric kettles, electric hair dryers, electric heaters and other electrical components such as switches, solenoid valves, power plugs, power sockets, brackets and so on.

Photovoltaic products: solar energy solar cell components such as junction boxes, power plugs and so on.

Automobile components: ignition system components, electric vehicle battery components, etc.

4. Halogen-free flame retardants in the application of flame retardant nylon

According to statistics, whether international or domestic, halogen-free flame retardants are widely used in nylon flame retardant. Only three kinds of halogen-free flame retardants, phosphorus, nitrogen and silicon, can reach 65.74% in SCI database and 43.34% in China Knowledge Network database.

Among them, phosphorus-containing flame retardants are most frequently used in the halogen-free flame retardant technology of nylon, and they are used more frequently in combination with other two kinds of flame retardants. At present, among the nylon flame retardant compounding systems, the one with more perfect research and widest application range is phosphorus-nitrogen compounding system, and the research on the mechanism of phosphorus-nitrogen synergistic flame retardant at home and abroad is getting more and more perfect.

Among them, phosphorus-containing flame retardants, including red phosphorus, phosphonite and melamine polyphosphate (MPP), have been applied more frequently in nylon flame retardancy.

Phosphorus flame retardants

According to the different structure and composition, they are divided into two categories: inorganic phosphorus-based and organic phosphorus-based flame retardants.

Inorganic phosphorus flame retardants mainly include red phosphorus, ammonium polyphosphate and phosphates, etc. Organic phosphorus flame retardants include phosphate esters, phosphite, phosphate esters and organic hypophosphites.

Although phosphorus flame retardants have high flame retardant efficiency, but in the process of use will release harmful phosphine gas, through the relevant modification can be effectively inhibited.

Nitrogen-containing flame retardants such as MCA

Melamine cyanurate (MCA) is the most researched, fastest growing and most widely used nitrogen flame retardant.

MCA not only has the flame retardant ability of general nitrogen flame retardant, but also can decompose cyanuric acid under heat to accelerate the degradation of the material and generate heat-shifted molten droplets, which generally only needs to be added to 10% or so, and the flame retardant property of the material can be greatly improved.

However, MCA and PA are less compatible, easy to absorb moisture, which will affect the mechanical and electrical properties of the material, and need to be modified in order to better put into practical use.

Inorganic flame retardants

Magnesium hydroxide, Sb2O3, zinc borate and other inorganic flame retardants have good thermal stability, flame retardant effect lasts longer, green, low toxicity, etc., but when used alone, the amount of additive needed to be larger, lower flame retardant efficiency, the impact on the mechanical properties of the base material is significant, mainly with other flame retardants used in combination.

Nano Flame Retardant System

In recent years, with the development of new materials and the advancement of research, inorganic nanomaterials represented by carbon nanotubes, POSS and graphene have gradually expanded their applications. Compared with the traditional flame retardants, nanomaterials, due to their microstructure and chemical structure, the materials obtained by surface modification or molecular structure design have a better gain effect.

5. Nylon flame retardant system development trend

Although, phosphorus and nitrogen flame retardants have been the main technology of nylon flame retardant, but in recent years, the defects of phosphorus and nitrogen flame retardant have gradually come to the fore, such as poor compatibility with the plastic matrix and the generation of toxic gases when phosphorus-containing flame retardants are burned, which have led to the limitation of their applications. The type of flame retardant, the amount added and its compatibility with the matrix and other factors will affect the mechanical properties of nylon composites.

Nano flame retardants, represented by montmorillonite, carbon nanotubes and POSS, are receiving more and more attention in academic research and technology development. By strengthening the interfacial effect, the compatibility between the flame retardant and the matrix can be enhanced, which is conducive to the flame retardant to play the role of flame retardant more efficiently, and, at the same time, it can also improve the overall performance of the composite material.

Therefore, the development of new organic-inorganic hybrid flame retardants, nano-flame retardants, or their use in combination with traditional flame retardants, and the exploration of synergistic mechanisms, may become a breakthrough point to improve the flame retardant efficiency and enhance the mechanical properties of nylon composites at the same time.

Conclusion

Flame retardant nylon materials have experienced continuous innovation and development in the past decades, from the initial halogenated flame retardant to the present halogen-free, nano-flame retardant and multifunctionalization, with its performance continuously optimized and application fields continuously expanded. Especially in the rapid rise of new energy industry, flame retardant nylon materials will play an important role in ensuring the safety and sustainable development of new energy field by virtue of its unique advantages.