Flame-retardant textiles can be seen everywhere in our lives, and their applications cover many fields such as daily life, industry, agriculture, medical defense, aerospace, transportation, and military.
So, do you know how flame-retardant textiles achieve flame-retardant effects?
Flame retardant mechanism Most of the textiles in our daily life are chemical fibers, cellulose fibers or multiple fibers It is made of blended and interwoven fibers. Under heat source conditions, heat can crack the fiber material and produce flammable substances. These decomposition products will continue to oxidize and burn in the flame, and release a large amount of heat, thereby promoting the continued cracking of fiber materials and accelerating combustion. The conditions for fabric burning are: combustibles, combustion-supporting substances and fire sources. Only by analyzing the combustion conditions and processes can different flame retardant mechanisms be adopted based on the combustion process.
The flame retardant finishing refers to the post-finishing of the fabric to reduce the flammability when exposed to external heat sources, delay the spread of combustion, and reduce the flame energy after the external heat source is removed. Extinguishes quickly. For the burning process of fabrics, flame retardancy is to cut off the circulation system of the interaction between the heat source, fabric and oxygen.
1. Covering layer flame retardant mechanism
Covered flame retardant is a chemical change that occurs when the flame retardant is heated and burns, producing flame-retardant substances on the surface of the textile, forming an insulating covering layer.
This covering film can block the interaction between the fabric and oxygen and heat sources, and can hinder the diffusion of flammable gases, thus playing a flame retardant role. Both inorganic and organic flame retardants have a covering flame retardant mechanism. For example, ammonium polyphosphate flame retardants adopt a covering flame retardant mechanism.
2. Vapor phase flame retardant mechanism
The main mechanism of gas phase flame retardancy There are two theories:
One is the gas dilution theory. Since the flame retardant is thermally decomposed to produce non-flammable gases, the concentration of flammable gases is diluted, resulting in insufficient oxygen during the burning process of the fabric, thereby achieving the flame retardant effect.
The second is the free radical theory. The thermal cracking products of flame retardants can interrupt the combustion chain reaction, because the cracking products can capture a large amount of high-energy oxygen free radicals and hydrogen free radicals during the combustion process, thereby exerting a flame retardant effect.
3. Decomposition of endothermic flame retardant mechanism
Flame retardant In the heated state, endothermic decomposition reactions such as phase change, dehydration, etc. occur. Because the flame retardant can absorb a certain amount of heat energy and reduce the heating of the fabric, it reduces the thermal decomposition of the fabric and the generation of flammable gases.
4. Dehydration and carbonization flame retardant mechanism
The role of flame retardants in During the heating process, the thermal cracking of the fiber is changed to promote the dehydration, cyclization and cross-linking of the fiber, thereby forming a carbon layer.
The formation of the carbon layer can reduce the generation of flammable gases and can also cover and insulate fabrics. Most of the flame retardants that use this flame retardant mechanism are phosphorus-containing. Flame retardants. It is generally believed that phosphates and organic phosphate compounds have a flame retardant effect because they undergo an esterification reaction with the hydroxyl groups in the fiber macromolecules, preventing the formation of L-glucose, further dehydrating the cellulose, and generating unsaturated double bonds. It speeds up the cross-linking reaction between cellulose molecules, increases the carbon residue generation rate of the fabric, and achieves the purpose of flame retardancy.
In actual production applications, the tissue structure and fiber content of fabrics are different, and the corresponding types of flame retardants are also different, so the actual flame retardant effect is The flame retardant mechanism is not single-determined. The flame retardant mechanism of a flame retardant may involve the combined effect of the above several flame retardant mechanisms.
When flame retardants or flame retardant ingredients with different flame retardant mechanisms work together, they will often produce better flame retardant effects due to the synergistic effect between them. There are two explanations for this synergistic effect. One is that the effect of multiple flame retardants or flame retardant ingredients working together is much stronger than the effect of using one alone;
Another explanation is that adding non-flame retardant components to the flame retardant system can increase the flame retardant capability. Such as the phosphorus-nitrogen synergistic effect. Among them, nitrogen-containing compounds such as urea and peptide amine have no flame retardant ability. However, when they are combined with phosphorus-containing flame retardants to finish fabrics, it is found that their flame retardant effects are better than those containing only phosphorus-containing flame retardants. Phosphorus flame retardants have better flame retardant effects. </p
