The spread of fire is essentially a continuous cycle of the three elements of “fuel oxygen temperature”: materials are decomposed by heat to produce combustible gases, which are ignited after mixing with oxygen. The heat released by combustion will further promote the decomposition of more materials, forming a vicious cycle.
The reason why fire-resistant non-woven fabric can “strangle” the throat of flames lies in its precise cutting of key links in this cycle through multiple flame retardant mechanisms – either preventing the production of combustible gases, isolating oxygen and heat, or directly interrupting combustion reactions, ultimately achieving the protective effect of “non combustible, difficult to ignite, or suppressing flame spread”. The flame retardant mechanism is not a single function, but a synergistic combination of three core mechanisms: gas-phase flame retardant, condensed phase flame retardant, and physical barrier. The specific analysis is as follows:
Gas phase flame retardant: interrupting the reaction chain at the “source” of combustion
The core logic of gas-phase flame retardant is: in the gas-phase region of flame combustion (i.e. the space where combustible gas and oxygen mix and burn), the release of flame retardant components “interferes” with the combustion reaction, preventing the continuous transmission of the combustion chain and rapidly suppressing flame spread. This mechanism is equivalent to directly cutting the bottom of the flame’s “fuel supply chain”.
Fireproof non-woven fabric achieves gas-phase flame retardancy mainly through two core methods: one is to add flame retardants containing halogen, phosphorus and nitrogen elements. When the material is heated, the flame retardants will decompose and produce inert gases such as hydrogen halides, nitrogen, ammonia, etc.
On the one hand, these gases dilute the oxygen in the air and the concentration of combustible gases produced by material decomposition, reducing the activity of combustion reactions; On the other hand, gases such as hydrogen halides can also capture hydroxyl radicals (· OH) and hydrogen radicals (· H) generated during combustion – these radicals are the “key messengers” that maintain the combustion chain reaction. Once captured in large quantities, the combustion chain will break and the flame will quickly extinguish.
The second is the nano composite flame retardant technology used in some high-end fire-resistant non-woven fabrics. Nanoparticles release active ingredients at high temperatures, which can efficiently capture combustion free radicals and enhance the gas-phase flame retardant effect.
It is worth noting that with the tightening of environmental regulations, traditional halogenated flame retardants are gradually being replaced by halogen-free phosphorus nitrogen flame retardants due to the potential production of toxic gases during combustion. This type of halogen-free flame retardant can not only achieve gas-phase flame retardancy, but also simultaneously exert condensed phase flame retardancy, which is more in line with the environmental and safety requirements of public facilities, medical care, transportation and other scenarios.
Condensed phase flame retardant: allowing materials to “refuse” the production of combustible fuels
The action area of condensed phase flame retardant is the fireproof non-woven fabric itself (i.e. the solid phase/condensed phase of combustion reaction), and the core is to suppress the thermal decomposition of materials and reduce the production of combustible gases through chemical or physical actions – without “fuel”, flames naturally cannot continue to spread. This mechanism is equivalent to putting a layer of “anti decomposition armor” on the fireproof non-woven fabric, reducing its flammability from the root.
Specifically, the flame retardancy of condensed phase is mainly achieved through three pathways:
Firstly, catalytic conversion into carbon. The phosphorus and boron flame retardants added to fire-resistant non-woven fabrics will decompose at high temperatures to produce acidic catalysts, which promote cross-linking and cyclization reactions of the fiber substrates (such as polyester, polypropylene, etc.) of the non-woven fabric, forming a dense carbonized layer.The carbonized layer itself is non combustible and can prevent further decomposition of fibers, thereby reducing the release of combustible gases;
Secondly, dehydrate into charcoal. Some flame retardants will undergo dehydration reactions with hydroxyl groups (- OH) in fibers at high temperatures, rapidly converting the fibers into carbonaceous residues and releasing water vapor. Water vapor not only dilutes combustible gases but also absorbs a large amount of heat, reducing the surface temperature of the material and delaying the decomposition process;
Thirdly, suppress molten dripping. For fiber substrates such as polyester that are prone to melting and dripping, flame retardants can enhance the thermal stability of the fibers, prevent the material from melting and dripping to form a “secondary fire source” when heated, and further block the path of fire spread.
Physical barrier: Building a ‘firewall’ to isolate heat and oxygen
When flames come into contact with fire-resistant non-woven fabrics, in addition to the chemical flame retardant effect, the physical structure of the material itself also forms a “physical firewall”, which further inhibits combustion by isolating oxygen and blocking heat transfer. This mechanism is an important supplement to chemical flame retardancy, which can significantly enhance the sustained protective ability of fire-resistant non-woven fabrics.
The core of physical barrier lies in the formation and maintenance of the carbonization layer. On the one hand, as mentioned earlier, the dense carbonization layer formed by flame retardants catalyzing fibers is a natural “thermal and oxygen barrier” – it can block the heat generated by flames from transferring to the interior of the material, avoiding further thermal decomposition of internal fibers.
At the same time, the carbonized layer has a tight structure, which can prevent external oxygen from entering the material and cut off the “oxygen supply” for combustion. On the other hand, the fiber interweaving structure of fire-resistant non-woven fabrics also plays a key role: compared to traditional textile fabrics, the fibers of non-woven fabrics are randomly interwoven, with controllable porosity and uniform distribution. The carbonized layer formed at high temperatures can better maintain structural integrity and is not easily broken, thus maintaining the barrier effect for a long time.
Part of the high weight fire-resistant non-woven fabric will also adopt a multi-layer composite structure, with fiber layers of different densities stacked together to further enhance its insulation and oxygen barrier properties. Even if the outer layer is carbonized, the inner layer can still remain stable, providing critical time for personnel evacuation or equipment protection.
Collaborative flame retardant: a combination of three mechanisms to build a strong safety defense line
It should be emphasized that in practical applications, the flame retardant effect of fire-resistant non-woven fabrics is not the result of a single mechanism, but a synergistic combination of gas-phase flame retardant, condensed phase flame retardant, and physical barrier. For example, when a flame comes into contact with a material, it first blocks some of the heat through its physical structure;
Subsequently, the flame retardant decomposes, capturing free radicals in the gas phase region, diluting combustible gases, and rapidly suppressing flame intensity;
At the same time, the catalytic carbonization reaction of condensed phase forms a dense carbonized layer, further isolating heat and oxygen, ultimately achieving a comprehensive effect of “rapid flame suppression, non spreading, and low smoke toxicity”.
The emphasis on the flame retardant mechanism of fire-resistant non-woven fabrics in different scenarios may vary. For example, fire-resistant non-woven fabrics used in firefighting suits pay more attention to the coordination of condensed phase flame retardant and physical barrier, ensuring that they do not melt or break at high temperatures and providing continuous protection for users.
Fireproof non-woven fabric used for sound absorption in public facilities will take into account the low smoke and toxicity characteristics of gas-phase flame retardancy, avoiding the production of toxic gases during combustion that can harm human health. But regardless of the focus, its core is to precisely cut off the cycle of the three elements of combustion, firmly “strangle” the throat of the flame, and become a key defense line for fire safety.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Dec-23-2025