preface:
Red phosphorus is extremely flammable - it is the main raw material for the production of matches. It seems inconceivable to use red phosphorus as a flame retardant, but red phosphorus is a highly effective flame retardant, especially for plastics; however, in resin, the process of red phosphorus and other phosphorus containing flame retardants is not simply oxidation, and phosphorus containing flame retardants mainly function in the condensed phase.
The flame retardant mechanism is as follows:
① The formation of carbon reduces the heat conduction from flame to condensed phase, and can play an isolation role.
② Phosphoric acid can absorb heat because it prevents CO from being oxidized to CO2 and reduces the heating process.
③ , forming a thin glass like or liquid protective layer for the condensed phase, thus reducing the diffusion of oxygen and the heat and mass transfer between the gas phase and the solid phase, inhibiting the carbon oxidation process, and reducing the concentration of combustible substances and gases.
④ The thermal decomposition of phosphorus containing flame retardant changes as follows: phosphorus flame retardant → phosphoric acid metaphase → phosphoric acid → polymetaphosphoric acid, which is a stable compound that is not volatile and has strong dehydration property, and is isolated from the air in the polymer surface compound; A large amount of heat is absorbed by the water vapor, which makes the flame retardant on the polymer surface decompose and release volatile phosphide. The mass spectrum analysis shows that the concentration of hydrogen atom is greatly reduced, which shows that Po · can also capture h ·, that is, Po · + H · = HPO.
End
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