Flame retardant mechanism of phosphorus flame retardant-PVC external lubricant
①The formation of phosphoric acid is used as a dehydrating agent and promotes the formation of char. The formation of char reduces the heat transfer from the flame to the condensed phase.
② Phosphoric acid can absorb heat because it prevents the oxidation of CO to CO2 and reduces the heating process.
③ A thin glassy or liquid protective layer is formed 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 phosphorus-containing flame retardant The thermal decomposition changes as follows: phosphorus flame retardant → phosphoric acid meta → phosphoric acid → polymetaphosphoric acid. Polymetaphosphoric acid is a stable compound that is not volatile and has strong dehydration properties. It is compounded on the polymer surface and isolated from the air; Absorbing a lot of heat, the flame retardant on the polymer surface is thermally decomposed to release volatile phosphides. Mass spectrometry analysis shows that the concentration of hydrogen atoms is greatly reduced, indicating that PO* captures H*, that is, PO*+H*=HPO.
PVC external lubricant
Phosphorus-based flame retardants have poor flame retardant effect when used alone. Phosphorus-based flame retardants play a flame-retardant effect by promoting dehydration and carbonization during the initial decomposition of high polymers. This dehydration carbonization step must rely on the oxygen-containing groups of the polymer itself, and for polymers with oxygen-containing groups in their structure. Their flame retardant effect will be better. For polypropylene, because its molecular structure does not have oxygen-containing groups, the flame retardant effect is not good when using phosphorus flame retardants alone, but if it is compounded with Al(0H)3 and Mg(OH)2, it will It can produce a synergistic effect, thereby obtaining a good flame retardant effect.