Typical flame retardant principle of halogen-free flame retardant

Phosphorus compounds and metal hydroxides are the most common, safe flame retardant chemicals. When these two kinds of compounds are burned, they produce no volatile or corrosive gases. The following are the principles of flame suppression without #halogen :

1 - THERMAL ABSORPTION

Any calories released in a short period of time are limited. If you can capture a portion of the heat emitted by the fire source in a brief period of time, the flame temperature will be decreased, radiating to the burning surface, and function will be improved. The calories of the combustible molecules that have been gasified into free radicals will be diminished, and the combustion process will be partially repressed. The flame retardant has a strong heat absorption reaction under high-temperature conditions, absorbing some of the heat released by combustion, lowering the temperature of the combustible material's surface, effectively inhibiting the production of combustible gases, and preventing the spread of combustion.?

The flame retardant process of #aluminumhydroxide is to improve the polymer's thermal capacity, enabling it to take in more calories before hitting the thermal decomposition point and thus increasing its flame retardant performance. When combining water and steam, this form of flame retardant fully exploits the characteristics of high heat absorption to enhance its own flame retardant ability.

2 - COVERING EFFECT

When flame retardants are added to combustible materials, they can create glassy or solid foam covering layers at high temperatures, which can separate oxygen and have the functions of heat insulation, oxygen isolation, and preventing flammable vapors from fleeing. When heated, organic phosphorus flame retardants, for example, can create cross-linked solid compounds or carbonized layers with more durable structures. On the one hand, the carbonized layer can prevent further pyrolysis of the polymer, and on the other, it can prevent internal thermal decomposition products from accessing the gas phase and participating in the combustion process.

3 - CHAIN REACTION INHIBITION

According to the chain reaction theory of combustion, free radicals are required to sustain combustion. Flame retardants can work on the gas phase combustion zone to capture free radicals in the combustion reaction, stopping the flame from spreading, decreasing flame density in the combustion zone, and ultimately slowing the combustion reaction until it stops. The vaporization temperature of a halogen-containing flame retardant, for example, is the same as or near the polymer's breakdown temperature. When the polymer decomposes due to heat, the flame suppressant is also vaporized.?At this time, the halogen-containing flame retardant and the thermal decomposition product are both in the gas-phase combustion zone, and the halogen can capture free radicals in the combustion reaction, preventing flame spread, reducing flame density in the combustion zone, and finally slowing the combustion reaction rate until it stops.

4 - NO GAS SUFFOCATION EFFECT

When the flame retardant is heated, the quantity of the combustible gas that escapes is reduced to below the lower limit of burning. At the same time, it dilutes the oxygen content in the burning region, keeping it from remaining flame retardant.