Chlorinated Flame Retardant

Chlorinated Flame Retardants

Chlorine-based flame retardants (CFR) are still widely used flame retardants due to their low price. Chlorine-based flame retardants are developing in the direction of no pollution, high purity, high thermal stability and high chlorine content. Alfa Chemistry offers you an extensive catalog of chlorinated flame retardants.

Flame Retardant Mechanism of CFR

CFR works by interfering with the combustion cycle in the gas phase. When CFR is exposed to fire and heat, it decomposes to generate free radical Cl·, which then reacts with H· to generate hydrogen bromide. Hydrogen bromide reacts with highly active ·OH radicals, on the one hand, it regenerates Cl, and on the other hand, it reduces the concentration of OH radicals, which inhibits the chain reaction of combustion and slows down the combustion speed until it is extinguished.

Chlorinated Flame RetardantsGas phase flame retardant mechanism


Common chlorinated flame retardants and their characteristics and uses are summarized in the following table.

Chlorinated ParaffinResinous white powder, chlorine content 68-72%, softening point 95-120°C, soluble in mineral oil, aromatic, ether, chlorinated, ketone, ester, etc. As an additive flame retardant, it has good lasting flame retardancy, low volatility, moisture-proof and anti-static effects, and can improve the fluidity of resin molding and modify the gloss of products.Mainly used for flame retardant of PE, PS, PMMA, synthetic rubber and textiles, and can also be used for fire retardant coatings.
Bis(hexachlorocyclopentadiene)cyclooctaneWhite crystalline dispersible solid, chlorine content 65.1%, melting point 350 °C.Mainly used in neoprene, natural rubber, silicone rubber, epoxy resin, PA, phenolic resin, unsaturated polyester, ABS, HIPS, PBT, PE, PP, and PUR, etc.
HexachlorocyclopentadieneLight yellow oily liquid, industrial chlorine content 76-79%, melting point 236-238°C, insoluble in water, soluble in ether, carbon tetrachloride, etc.As a reactive flame retardant, flame retardant for polyurethane polyester resin.
Chlorine Anhydride (HET)White crystal, low volatility at room temperature, melting point 240-245 °C, soluble in benzene, ethane, acetone, etc.Mainly used as a reactive flame retardant, it can be used as a flame retardant for PET and polyurethane, and as a curing agent for epoxy resins.

Research Information

The mechanism of action of organochlorine flame retardants is similar to that of organobromine flame retardants, but they are not as efficient as brominated flame retardants, and are usually used together with antimony oxide. A study explored the possibility of using zinc hydroxystannate as an alternative synergist for antimony trioxide. Zinc hydroxystannate (ZHS) was found to be a good alternative synergist for antimony trioxide, especially in reducing heat release rate and smoke generation. It is recommended to use ZHS with chlorinated paraffins, tetrachlorophthalic anhydride, chloroalkene anhydride. [1]

Comparison of the FR properties of ZHS and Sb2O3 Comparison of the FR properties of ZHS and Sb2O3 [1]

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  1. P.A. Cusack, et al. (1997). "Zinc hydroxystannate as an alternative synergist to antimony trioxide in polyester resins containing halogenated flame retardants," Polymer Degradation and Stability 58(1–2), 229-237.
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