Ammonium polyphosphate

Ammonium polyphosphate (APP) is an inorganic compound primarily used as a flame retardant. It is a salt of ammonium and polyphosphoric acid. It has the formula (NH4)n+2PnO3n+1 and is a colorless, inorganic salt.

Chemical Structure

Ammonium polyphosphate exists in two forms: crystalline (phase II) and amorphous. The crystalline form is water-insoluble, while the amorphous form is water-soluble. The crystalline form is more thermally stable and is often used in applications requiring high thermal stability.

Production

Ammonium polyphosphate is produced by the reaction of ammonia with phosphoric acid. The reaction is exothermic and results in the formation of ammonium polyphosphate and water.

Applications

Ammonium polyphosphate is widely used as a flame retardant in a variety of applications. It is used in the production of intumescent coatings, which swell and form a protective layer when exposed to heat. It is also used in the production of flame-retardant polymers and resins, such as polyvinyl chloride (PVC) and polyurethane (PU).

Safety

Ammonium polyphosphate is generally considered safe for use. However, it can cause irritation to the eyes, skin, and respiratory tract if not handled properly. It is recommended to use personal protective equipment when handling this chemical.

Environmental Impact

Ammonium polyphosphate is not considered to be a significant environmental hazard. However, it can contribute to eutrophication if released into water bodies in large quantities.

See Also

• Ammonium
• Polyphosphoric acid
• Flame retardant
• Intumescent