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How to achieve flame retardant modification of modified plastics?

2024-07-21 11:14

The application of modified plastics in home appliances, electronic appliances, automobiles and other fields often requires flame retardancy, and flame retardant modification can be achieved by adding flame retardants. There are bromine flame retardants and halogen-free flame retardants.
Flame retardants
Flame retardants are also called flame retardants, fire retardants or fireproofing agents, which are functional additives that give flammable polymers flame retardancy. Most of them are compounds of elements in the VA (phosphorus), VIIA (bromine, chlorine) and ⅢA (antimony, aluminum) groups in the periodic table.
Principle of flame retardant of modified plastics
1. Endothermic effect
The heat released by any combustion in a short time is limited. If a part of the heat released by the fire source can be absorbed in a short time, the flame temperature will be reduced, and the heat radiated to the combustion surface and acting on the decomposition of the already gasified combustible molecules into free radicals will be reduced, and the combustion reaction will be inhibited to a certain extent.
Under high temperature conditions, the flame retardant undergoes a strong endothermic reaction, absorbs part of the heat released by the combustion, reduces the temperature of the combustible surface, effectively inhibits the generation of combustible gases, and prevents the spread of combustion.
2. Covering effect
After adding flame retardant to combustible materials, the flame retardant can form a glassy or stable foam covering layer at high temperature, isolating oxygen, and has the effects of heat insulation, oxygen isolation, and preventing the escape of combustible gases, thereby achieving the purpose of flame retardancy.
For example, organic phosphorus-blocking flame retardants can produce cross-linked solid substances or carbonized layers with more stable structures when heated. The formation of the carbonized layer can prevent the polymer from further pyrolysis on the one hand, and on the other hand, it can prevent the thermal decomposition products inside it from entering the gas phase to participate in the combustion process.
3. Inhibition of chain reaction
According to the chain reaction theory of combustion, free radicals are required to maintain combustion. Flame retardants can act on the gas phase combustion zone, capture free radicals in the combustion reaction, thereby preventing the spread of flames, reducing the flame density in the combustion zone, and finally reducing the combustion reaction rate until it stops.
4. Asphyxiation effect of non-combustible gas
When heated, the flame retardant decomposes non-combustible gas, diluting the concentration of combustible gas decomposed from the combustible to below the lower limit of combustion. At the same time, it also has a diluting effect on the oxygen concentration in the combustion zone, preventing the continuation of combustion, and achieving the effect of flame retardancy.