The flame-retardant mechanism of aluminum hydroxide: When the temperature exceeds 200 ºC, aluminum hydroxide begins to endothermic and decomposes and releases three crystal waters. The decomposition rate is the largest at about 250 ºC,which is: 2Al(OH)3 → Al2O3 + 3H2O↑ .This reaction is a strong endothermic reaction during inhibiting the rise of polymer temperature, reducing its decomposition rate, and only producing water vapor without generating toxic and harmful gases.
The flame retardant mechanism can be summarized as follows:
1) Endothermic effect:Dehydration at 300~350 ºC absorbs heat and inhibits the temperature rise of the polymer;
2) Dilution effect:ATH filling reduces the concentration of flammable polymers. The water vapor released by ATH dehydration dilutes the concentration of combustible gas and oxygen, which can prevent combustion;
3) Covering effect:After ATH is dehydrated, an Al2O3 protective film is formed on the surface of combustibles, which isolates oxygen and prevents continued combustion;
4) Carbonization:Flame retardants produce strong dehydrating substances under burning conditions, carbonize plastics and are not easy to produce flammable volatiles, so preventing the spread of flames.