How do flame retardants achieve flame retardant effect?
Flame retardants exert their flame retardant effects through several mechanisms, such as endothermic effect, covering effect, inhibition of chain reaction, and asphyxiation of non-combustible gases. Most flame retardants achieve the purpose of flame retardancy through the joint action of several mechanisms. It is generally believed that a halogen compound undergoes a decomposition reaction when exposed to fire, and the decomposed halogen ion reacts with a polymer compound to generate a hydrogen halide. The latter reacts with a large number of active hydroxyl radicals (HO ·) that proliferate during the combustion of polymer compounds, reducing their concentration and slowing down the combustion rate until the flame is extinguished. Among halogens, bromine has a greater flame retardant effect than chlorine. The role of phosphorus-containing flame retardants is that they form when they burn.
flame retardantIt exerts its flame retardant effect through several mechanisms, such as endothermic effect, covering effect, inhibition of chain reaction, asphyxiation of non-combustible gas, etc. Most flame retardants achieve the purpose of flame retardancy through the joint action of several mechanisms. It is generally believed that a halogen compound undergoes a decomposition reaction when exposed to fire, and the decomposed halogen ion reacts with a polymer compound to generate a hydrogen halide. The latter reacts with a large number of active hydroxyl radicals (HO ·) that proliferate during the combustion of polymer compounds, reducing their concentration and slowing down the combustion rate until the flame is extinguished. Among halogens, bromine has a greater flame retardant effect than chlorine. The function of phosphorus-containing flame retardants is that when they burn, they form metaphosphoric acid, which polymerizes into a very stable polymeric state, which becomes a protective layer of the plastic and isolates oxygen.
1. Endothermic effect
Any combustion in a short period of time the release of heat is limited, if you can in a short period of time to absorb part of the heat released by the fire, then the flame temperature will be reduced, radiation to the combustion surface and the role of the combustible molecules have been vaporized into free radicals of heat will be reduced, the combustion reaction will be a certain degree of inhibition. Under high temperature conditions, the flame retardant has a strong endothermic reaction, absorbs part of the heat released by combustion, reduces the temperature of the combustible surface, effectively inhibits the generation of flammable gases, and prevents the spread of combustion. The flame retardant mechanism of Al(OH)3 flame retardant is to increase the heat capacity of the polymer, so that it can absorb more heat before reaching the thermal decomposition temperature, thereby improving its flame retardant performance. This kind of flame retardant gives full play to its characteristics of absorbing a lot of heat when combined with water vapor, and improves its own flame retardant ability.
2. The role of coverage
After the flame retardant is added to the combustible material, the flame retardant can form a glassy or stable foam coating at high temperature, isolate oxygen, have heat insulation, oxygen barrier, and prevent the escape of combustible gas, so as to achieve the purpose of flame retardant. For example, when the organic phosphorus flame retardant is heated, it can produce a cross-linked solid substance or a carbonized layer with a more stable structure. On the one hand, the formation of the carbonized layer can prevent the further pyrolysis of the polymer, on the other hand, it can prevent the internal thermal decomposition organisms from entering the gas phase to participate in the combustion process.
Inhibition of chain reactions
According to the chain reaction theory of combustion, what is needed to sustain combustion is free radicals. The flame retardant can act on the gas phase combustion zone to capture the free radicals in the combustion reaction, thereby preventing the spread of the flame, reducing the flame density in the combustion zone, and finally reducing the combustion reaction speed until the end. Such as halogen-containing flame retardants, its evaporation temperature and polymer decomposition temperature is the same or similar, when the polymer is decomposed by heat, the flame retardant is also volatilized. At this time, the halogen-containing flame retardant and the thermal decomposition product are in the gas phase combustion zone at the same time, and the halogen can capture the free radicals in the combustion reaction and interfere with the combustion chain reaction.
4. Asphyxiation effect of non-combustible gas
When the flame retardant is heated, the non-combustible gas is decomposed, and the concentration of the combustible gas decomposed by the combustible material is diluted below the lower limit of combustion. At the same time, it also has a dilution effect on the oxygen concentration in the combustion zone, preventing the combustion from continuing and achieving the flame retardant effect.
Real-time information
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Everyone knows that there are two common flame retardants. Today we are going to talk about only one of them. Aluminum hydroxide flame retardant is an environmentally friendly halogen-free flame retardant, which can be widely used in fabrics, wood, plastics, and rubber., Polyurethane and other industries have ideal flame retardant effect. In the process of industrial application, it is found that flame retardant failure occurs when aluminum hydroxide flame retardant is added. The following are the reasons for the failure of aluminum hydroxide flame retardant, how to prevent it, how to deal with the operation, and restore the original function.
As a flame retardant, magnesium hydroxide also need to improve what aspects?
When it comes to flame retardants, everyone is familiar with them. Although we usually have less contact with them, we can know what they are used for from the name. Have to talk about magnesium hydroxide, we all know that its main presentation state is a granular, at present, the market sales of magnesium hydroxide particle size is larger, part of the commodity particle size up to tens of microns, immediately used as a flame retardant, poor dispersion, the physical properties of raw materials greater harm. In industrial production, physical grinding methods are generally used to reduce the particle size to 1 micron. The surface of magnesium hydroxide has high polarity and is easy to agglomerate. As the compatibility of refractory materials and polymer substrates, it not only reduces its flame retardant grade, but also causes more serious harm to the physical properties of raw materials.
Hefei Zhongke Flame Retardant New Material Co., Ltd
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Ministry of Foreign Trade Telephone:13956052398
Comprehensive department Telephone:0551-67712199
Company headquarters address: Hefei Feidong Economic Development Zone Xianghe Road 36
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