The principle of gas sources in intumescent flame retardants is mainly reflected in the following aspects:
Thermal decomposition: A gas source usually refers to a compound that can decompose and release a large amount of non-toxic and non-flammable gas when heated. For instance, commonly used gas sources include melamine, dicyandiamide, ammonium polyphosphate (APP), urea, etc. These substances will decompose when heated, generating inert gases such as ammonia and carbon dioxide.
Formation of an expanded carbon layer: During the combustion process, the gas produced by the decomposition of the gas source causes the already molten system to expand and foam. These gases fill the carbon layer, causing it to expand and form a porous foam structure. This structure not only increases the thickness of the carbon layer, but also enhances its heat insulation and oxygen isolation capabilities.
Synergistic effect: The gas source works in synergy with the acid source and carbon source. When heated, the acid source decomposes to produce acidic substances, promoting the dehydration and carbonization of the carbon source and forming a carbon layer. Meanwhile, the gas released by the gas source causes the carbon layer to expand, thereby enhancing the flame retardant effect. The expanded carbon layer can more effectively isolate heat and oxygen, preventing the spread of flames.
Flame retardant mechanism: The expanded carbon layer achieves flame retardancy through the following mechanisms:
Insulation effect: The carbon layer acts as a barrier to prevent the transfer of heat into the interior of the material.
Oxygen isolation effect: The carbon layer prevents oxygen from entering the combustion area, interrupting the supply of oxygen required for combustion.
Smoke suppression and drip prevention: The carbon layer can also suppress the generation of smoke and prevent the material from melting and dripping due to combustion, reducing the risk of fire spread.
