Four functions of flame retardants

1. Flame retardant-cooling effect

Some flame retardants can absorb the heat released by the plastic when burning, reduce the temperature of the burning plastic, prevent it from continuing to degrade or crack, interrupt the source of combustible gas, and extinguish the flame, such as organophosphorus nitrogen intumescent flame retardants; for example, , Borax has 10 molecules of crystal water. Since the release of crystal water takes 141.8kJ/mol heat, the temperature rise of the material is suppressed due to its heat absorption, thereby producing a flame-retardant effect. The flame-retardant effect of hydrated alumina is also due to the endothermic effect produced by dehydration by heating. In addition, the droplets often produced by the pyrolysis of some thermoplastic polymers can also exert a certain flame retardant effect because they can leave the combustion zone to remove the heat of reaction.

2. Smoke suppression-isolation effect

Incombustible gas or foam layer is produced during the combustion process, or a liquid or solid covering layer is formed, so that the combustion process is stopped due to anaerobic supplementation, such as halogen flame retardants, expanded graphite, polyol and polyvinyl alcohol, etc.

The covering effect is to generate a stable covering layer at a higher temperature, or decompose to form a foam-like substance, which covers the surface of the polymer material, making it difficult for the heat generated by combustion to pass into the material, causing the polymer material to be heated by heat. The combustible gas generated by decomposition is difficult to escape, and acts as an air barrier to the material, thereby inhibiting the material from cracking and achieving the effect of flame retardancy. For example, phosphate compounds and fire-resistant foam coatings can function according to this mechanism.

3. Heat dissipation-eliminate free radicals

In the combustion process, it can eliminate the free radicals O· and OH· generated by cracking or pyrolysis, and cut off the source of combustible gases, such as halogen flame retardants, in the middle of the combustion chain reaction. The combustion of polymers is mainly a chain reaction of free radicals. Some substances can capture the active intermediates of combustion reaction HO·, H ·, ·O·, HOO·, etc., inhibit the chain reaction of free radicals, and reduce the burning speed until the flame is extinguished. Commonly used organic halogen compounds such as bromine and chlorine have this inhibitory effect.

4. Anti-drip—dilution effect

During combustion, it can release inert gas, dilute the concentration of combustible gas and oxygen in the combustion area, and make combustion impossible, such as boron compounds and molybdenum compounds.

Such substances can produce a large amount of non-combustible gas when they are decomposed by heat, so that the flammable gas produced by the polymer material and the oxygen in the air are diluted without reaching the flammable concentration range, thereby preventing the polymer material from igniting and burning. . CO2, NH3, HCl and H2O can be used as diluent gases. Amine phosphate, amine chloride, amine carbonate, etc. can generate this incombustible gas when heated

Shawn

Regional Sales Manager

Zhejiang Ruico Advanced Materials Co., Ltd. (Stock No.873233)

Add: No.188, Liangshan Road, Linghu Town, Nanxun District, Huzhou City, Zhejiang Province, China 313018

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