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Mechanism of typical flame retardant (liquefied MDI)

2020-07-24 21:00:31


Mechanism of typical flame retardants

The combustion of polymer is a very intense complex thermal oxidation reaction with the characteristics of emitting thick smoke blazing flame. The general process of combustion is that under the constant heating of external heat source, the polymer first reacts with oxygen in the air to produce volatile combustible materials. When the substance reaches a certain concentration temperature, it will ignite burn. Part of the heat released by combustion supplies the polymer being degraded, which further intensifies its degradation produces more combustible gases flames In a very short time, it will spread rapidly cause a fire.


Flame retardant is a kind of additive which can prevent plastic igniting flame spreading. According to the use method, it can be divided into two types: additive type reactive type. According to the chemical structure, flame retardants can be divided into inorganic organic. The flame retardant mechanism of all kinds of flame retardants is necessary necessary for today's flame retardant engineers. Today, we will summarize the flame retardant mechanism of several typical flame retardants.


Flame retardant mechanism of several typical flame retardants

Mechanism of halogen flame retardant

Halogenated flame retardants include bromine chlorine flame retardants. Halogenated flame retardant is one of the largest organic flame retardants in the world. Most of halogenated flame retardants are brominated flame retardants. The brominated flame retardants produced in industry can be divided into additive type, reactive type polymer type, there are many kinds of them. There are more than 20 kinds of additive brominated flame retardants, more than 10 kinds of polymer brominated flame retardants, more than 20 kinds of reactive brominated flame retardants in the domestic foreign markets. Additive flame retardants mainly include decabromodiphenyl ether (DBDPO), tetrabromobisphenol A, bis (2,3-dialkylpropyl) ether (TBAB), octabromodiphenyl ether (obdpo), etc.; reactive flame retardants mainly include tetrabromobisphenol A (TBBPA), 2,4,6-tribromophenol, etc.; polymer flame retardants mainly include brominated polystyrene, brominated epoxy, tetrabromobisphenol A carbonate oligomer, etc.







Flame retardant mechanism of inorganic flame retardant

Inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, expanded graphite, borate, aluminum oxalate zinc sulfide based flame retardants. Aluminum hydroxide magnesium hydroxide are the main varieties of inorganic flame retardants. They have the characteristics of non-toxic low smoke. Due to the absorption of a large amount of heat in the combustion zone by thermal decomposition, the temperature of the combustion zone is reduced below the critical temperature of combustion, the combustion is self extinguishing. Most of the metal oxides generated after decomposition have high melting point good thermal stability, which cover the surface of combustion solid phase to block heat conduction radiation, thus playing a flame retardant role. At the same time, a large amount of water vapor is produced by decomposition, which can dilute combustible gas also play a flame retardant role.


The synergistic effect of halogen-containing flame retardants phosphorus containing flame retardants is remarkable. For the synergistic effect of halogen phosphorus flame retardancy, it is proposed that halogen phosphorus compounds can promote the decomposition of each other, form halogen phosphorus compounds their conversion pbr3, PBR ·, pobr3, etc. The synergistic effect of halogen phosphorus was studied by pyrolysis gas chromatography, differential thermal analysis, differential scanning calorimetry, oxygen index determination temperature programmed observation of flame retardants. The results showed that the decomposition temperature of flame retardants was slightly lower than that of single halogen phosphorus flame retardants, the decomposition was often severe. The smoke cloud formed by chlorine phosphorus compounds their hydrolysates in the combustion zone could last a long time It remains in the combustion zone forms a strong gas phase isolation layer.



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