Halogenated Phosphate Ester Flame Retardants - Halogenated Phosphate Esters

(1) Tris(2-chloroethyl) Phosphate

Tris(2-chloroethyl) phosphate, also known as tris(2-chloroethyl) ester of phosphoric acid or tris(β-chloroethyl) phosphate, is abbreviated as TCEP. Its molecular formula is O==P(OCH₂CH₂Cl)₃, with a molecular weight of 286. It is a colorless liquid containing approximately 10.8% phosphorus and 37.2% chlorine. Its density at 25°C is 1.492 g/cm³, viscosity at 25°C is approximately 38 mPa·s, and its boiling point ranges from 210 to 220°C (2.7 kPa).

TCEP is one of the earliest, most widely used, and cheapest flame retardants. It is synthesized by the reaction of phosphorus oxychloride and ethylene oxide. It has good hydrolysis resistance and high flame retardancy but is prone to volatilization and has poor long-term effectiveness.

TCEP is suitable for both flexible and rigid polyurethane foams, but its performance is better in rigid foams. A disadvantage is its high required dosage, which, when exceeding 15%, can reduce the physical properties of the foam.

(2) Tris(2-chloropropyl) Phosphate

Tris(2-chloropropyl) phosphate, abbreviated as TCPP, is a colorless liquid with a density of 1.29 g/cm³ (25°C) and a viscosity of about 65 mPa·s (25°C). It is produced by reacting phosphorus oxychloride with propylene oxide. TCPP contains 9.5% phosphorus and 32.5% chlorine.

Compared to tris(chloroethyl) phosphate, TCPP has a lower phosphorus-to-chlorine ratio, resulting in slightly reduced flame-retardant efficiency. It exhibits poor durability in flexible foams but does not cause scorching issues in the foam. It is commonly used in rigid foams.

(3) Tris(dichloropropyl) Phosphate

Tris(dichloropropyl) phosphate, abbreviated as TDCPP, is a colorless to light yellow transparent viscous liquid. It is synthesized by the reaction of phosphorus oxychloride with epichlorohydrin. Its main structures are O==P(OCH(CH₂Cl)₂)₃ and O==P(OCHCICH₂CH₂Cl)₃, with a molecular weight of 428.

TDCPP contains 49.3% chlorine and 7.2% phosphorus. Its density at 25°C is 1.52 g/cm³, viscosity at 25°C is approximately 1800 mPa·s, solidification point is 5°C, flash point is 251.7°C, ignition point is 282°C, auto-ignition temperature is 513.9°C, and boiling point exceeds 200°C (533 Pa). Its refractive index at 25°C is 1.5019, and the initial decomposition temperature is 230°C.

Due to its high chlorine content, TDCPP provides excellent flame retardancy and long-lasting durability, with minimal impact on the physical properties of foams. It can be used in various polyurethane foams and other resins, predominantly in flexible foam production.

Other Halogenated Phosphate Esters

Other halogenated phosphate esters include tris(dibromopropyl) phosphate, bis-(2-halogenated ethyl)(3-bromo-2,2-dimethylpropyl) phosphate, bis(2,3-dibromopropyl) dichloropropyl phosphate, and tris(2-bromo-3-chloropropyl) phosphate.