The Principle of Flame Retardant
1. Plastic combustion process
The process of plastics combustion can be considered as follows: in the air, plastics are heated by external heat or fire source, which eventually leads to degradation, resulting in volatile products, flammable products and thermal energy products. Under the continuous action of external heat source, plastics will burn up at a certain temperature. Part of the heat released from plastic combustion is absorbed by degrading plastics through conduction, radiation and convection, and more flammable products are volatilized. On the other hand, in the process of combustion, the air around the flame disturbs violently, which increases the mixing speed of flammable volatiles and air, and makes the combustion more intense.
2. The action mechanism of flame retardant is that flame retardant is a substance that can prevent combustion, reduce combustion speed or increase ignition point. The mechanism of flame retardant is as follows:
2.1 The dehydration of the decomposition products of flame retardants causes carbonization of organic matter, which prevents the combustion of burning plastics from being decomposition combustion, whereas the evaporation combustion and decomposition combustion of elementary carbon which produces flames are usually not carried out. Therefore, combustion can be prevented if the thermal decomposition of the material can proceed rapidly, without stopping at the stage of combustible matter and decomposing until carbon.
2.2 Flame retardant decomposes into non-volatile protective film flame retardant, which decomposes at the temperature of plastic combustion. The decomposed product forms a non-volatile protective film covering the surface, thus separating the air from combustion.
2.3 The decomposition product of flame retardant can cut off the chain reaction of active free radicals by the chain reaction of active free radicals. The decomposition product of flame retardant can cut off the chain reaction of active free radicals to prevent flame combustion effectively.
2.4 Dispersion of combustion heat and dilution of flammable substances are one of the ways to achieve flame retardancy.
As the heat of combustion is absorbed in large quantities, the temperature of plastics is lowered, thus the decomposition, evaporation and combustion are slowed down. On the other hand, the plastic flame retardant system can decompose to produce non-flammable gases, thus diluting the flammable gases to achieve the purpose of flame retardant.
2.5 Oxygen Isolation of Heavier Gases or High Boiling Point Liquids
The water from the reaction absorbs a lot of heat, reduces the surface temperature of combustibles, and vaporizes into steam, forming a protective film on the surface of combustibles, thus achieving flame retardancy.
