Basic Principles of Flame Retardants
- time:
- 2019-05-11
Flame retardant is a chemical additive which plays an important role in industry, life and other fields. It can inhibit the flammability of materials and realize the ideal flame retardancy of materials. People's life and property security also brings a guarantee. The specific functions of flame retardants include the following aspects.
One
Non-combustible gas asphyxiation
When the flame retardant is heated, it will decompose into non-combustible gases, diluting the concentration of combustible gases decomposed from combustibles to the lower combustion limit. It also dilutes the oxygen concentration in the combustion range and successfully prevents the spread of the fire.
Two
Endothermic effect
The heat released by any combustion in a shorter time is limited. If a part of the heat released by the fire source can be absorbed in a shorter time, the flame temperature will be lowered. The heat radiated to the combustion surface and acting on cracking the gasified combustible molecules into free radicals will be reduced, and the combustion reaction will be inhibited to a certain extent. Under high temperature, the flame retardant has a strong endothermic reaction, which absorbs part of the heat released by combustion, reduces the surface temperature of combustible materials, effectively inhibits the formation of combustible gases and prevents the spread of combustion. The flame retardant mechanism of Al(OH)3 flame retardant is to improve the flame retardant performance by increasing the heat capacity of the polymer to absorb more heat before reaching the thermal decomposition temperature. This kind of flame retardant can give full play to its heat absorption characteristics when combined with water vapor, and improve its own flame retardant ability.
Three
Non-combustible gas asphyxiation
When the flame retardant is heated, it decomposes the non-combustible gas and dilutes the concentration of the combustible gas decomposed from the combustible matter to below the lower limit of combustion. At the same time, it can dilute the oxygen concentration in the combustion zone, prevent the combustion from proceeding and achieve flame retardant effect.
Four
Inhibitory chain reaction
According to the chain reaction theory of combustion, free radicals are needed to maintain combustion. Flame retardants can act on the gas phase combustion zone to capture free radicals in combustion reaction, thus preventing flame propagation, reducing the flame density in the combustion zone, and ultimately reducing the combustion reaction rate until the end. For example, the evaporation temperature and decomposition temperature of halogen-containing flame retardants are the same or similar. When the polymer is decomposed by heat, the flame retardants also volatilize at the same time. When halogen-containing flame retardants and thermal decomposition products are in the gas phase combustion zone at the same time, halogen can capture the free radicals in the combustion reaction, thus preventing the flame propagation, reducing the flame density in the combustion zone, and ultimately reducing the combustion reaction rate until the end.
