Halogenated Hydrocarbons and Other Halogen-Containing Flame Retardants

Halogenated alkanes and halogenated aromatic flame retardants can also be used in polyurethane foam. When used in combination with antimony trioxide, they exhibit a synergistic flame-retardant effect.

The general structural formula of polybrominated diphenyl ethers (PBDEs) is as follows, where the total number of substituted bromine atoms (x + y) on the two benzene rings can be 5, 8, 10, etc.

Pentabromodiphenyl ether contains five bromine atoms, with a bromine content of 69%–72%. It is an amber-colored, high-viscosity liquid with a relative density (25°C) of approximately 2.26 and viscosity (15°C) of 2.0 Pa·s. A mixture of pentabromodiphenyl ether and halogen-containing phosphate esters is particularly suitable for flexible polyurethane foam due to its high flame-retardant efficiency and excellent resistance to "charring."

Decabromodiphenyl ether has a relative molecular weight of 959 and a bromine content of 82%–83%. It has high flame-retardant efficiency and good thermal stability. It appears as a white or slightly yellow, free-flowing powder with a particle size generally smaller than 10 μm. Its relative density is 3.2, melting point is 300–310°C, and decomposition temperature is 425°C.

Poly(2,4-dibromophenyl ether) (PBO) has the molecular formula (C6H3Br2O)n with a relative molecular weight of 400–1200 (n = 6–35) and a bromine content of 62%. It is a gray to light brown polymer powder with a melting point of 210–240°C and a decomposition temperature of 360°C. PBO has good thermal stability, is compatible with many resins, and does not reduce the mechanical properties of the resins, making it suitable for polyurethane flame retardancy.

Tris(2,3-dibromopropyl) polyisocyanurate, abbreviated as TBC or TAIC-6B, is a light yellow to brown oily liquid with a relative molecular weight of 678 and a bromine content of 71%. It has a refractive index (25°C) of 1.5666. It is soluble in aromatics, acetone, and other organic solvents but insoluble in water.

This is an efficient flame retardant suitable for a variety of plastics, including polyolefins, PVC, polyurethane, unsaturated resins, synthetic rubber, and fiber polymers. It has good compatibility with polymers, low volatility, excellent durability, light stability, water resistance, and non-toxicity. It has a relative molecular weight of 729, a bromine content of 66%, and appears as a white crystalline powder at room temperature. It has a relative density of 2.50, an acid value of less than 0.5 mg KOH/g, and a melting point of 100–110°C.

A domestically produced flame retardant, BP60, is a phosphorus- and bromine-containing additive-type flame retardant. It can be used in flexible polyurethane foams and other resins, offering good flame retardancy, thermal stability, and hydrolysis resistance. It is soluble in polyols and appears as a yellow-brown viscous liquid with an acid value ≤1.0 mg KOH/g, bromine content of 58%–60%, and phosphorus content of 1.1%–1.4%.

Other halogenated flame retardants include tris(2,3-dibromopropyl) borate, tetrabromobisphenol A diallyl ether (TBE), pentabromoethylbenzene, decabromodiphenylethane, dibromophenyl glycidyl ether, chlorinated paraffins, brominated paraffins, bromo-chlorinated paraffins, octabromoether, tribromophenol, pentabromochlorocyclohexane, and hexachlorocyclopentadiene.