What is the flame-retardant mechanism of flame-retardant nonwoven fabrics for electrical applications?

2025-12-03 14:27:42

The flame-retardant mechanism of flame-retardant nonwoven fabrics for electrical applications is mainly based on the synergistic effect of chemical and physical flame retardancy. Chemical flame retardancy is achieved by adding flame retardants to polyester fibers. Common flame retardants include phosphorus-based, nitrogen-based, and halogen-based compounds. Phosphorus-based flame retardants decompose at high temperatures to generate phosphoric acid or polyphosphoric acid, promoting the formation of a dense char layer on the fiber surface, isolating oxygen and heat transfer. Nitrogen-based flame retardants release nitrogen to dilute the concentration of combustible gases and simultaneously produce a synergistic effect with phosphorus-based flame retardants, enhancing the flame-retardant effect. Halogen-based flame retardants mainly interrupt the combustion process by capturing free radicals in the combustion chain reaction, but their application is gradually decreasing due to environmental restrictions.

The physical flame-retardant mechanism relies on the structural characteristics of the nonwoven fabric. The porous structure of the fibers slows down the diffusion rate of heat and oxygen, inhibiting flame spread. The air layer between fibers has a heat-insulating effect, reducing the material's thermal conductivity. In addition, the high specific surface area of the nonwoven fabric helps to uniformly distribute the flame retardant, ensuring consistent flame-retardant performance. Flame-retardant properties can be further controlled by optimizing fiber arrangement density and porosity.

The durability of the flame-retardant mechanism is also an important consideration. High-quality flame-retardant nonwoven fabrics must ensure a strong bond between the flame retardant and the fiber, preventing loss due to environmental factors (such as humidity or ultraviolet radiation). Chemically bonded flame retardants, bound to the fiber via covalent bonds, are more resistant to migration and volatilization than physically mixed flame retardants. Simultaneously, fiber surface treatments (such as plasma modification) can enhance the adhesion and stability of the flame retardant.

Comprehensive evaluation of flame-retardant performance requires consideration of multiple aspects. In addition to the ability to suppress flame propagation, smoke density and toxic gas release during combustion must also be considered. Low smoke and low toxicity are important characteristics of electrical flame-retardant nonwoven fabrics, especially crucial in enclosed electrical equipment. Through the design of composite flame-retardant systems, such as the combined use of synergistic flame retardants, more comprehensive fire safety performance can be achieved.