Ammonium polyphosphate (APP) is an organic salt of polyphosphoric acid and ammonia. As a chemical, it is non-toxic, environmentally friendly and halogen-free. It is most commonly used as a flame retardant, selection of the specific grade of ammonium polyphosphate can be determined by the solubility, Phosphorus content, chain length and polymerization degree. The chain length (n) of this polymeric compound can be linear or branched. Depending on the polymerization degree, there are two main families of ammonium polyphosphate: Crystal phase I APP (or APP I), and Crystal phase II APP (or APP II).
- APP phase I has a short and linear chain (n < 100), it is more water sensitive (hydrolysis) and less thermally stable; actually it begins to decompose at temperatures above 150 °C.
- The second family of Ammonium polyphosphate is the APP Phase II; which has an high polymerization degree, with n>1000, its structure is cross linked (branched), and it is an high-quality non-halogenated flame retardant. APP phase II, Ammonium polyphosphate, has an higher thermal stability (the decomposition starts at approximately 300°C) and lower water solubility than APP I.
| Appearance |
White free-flowing powder |
| Whiteness |
92.0 Min |
| pH (10% slurry -25°C) |
5.5-7.5 |
| Acid Value, KOH mg/1g |
1.0 Max |
| Solubility in water (25°C), g/100ml H2O |
0.50 Max |
| Nitrogen, w/w% |
14.0-15.0 |
| Phosphorus (P), w/w% |
31.0-32.0 |
| Thermal decomposition onset, °C |
285 Min |
| Average Particle Size, D50, µm |
About 15 |
Ammonium Polyphosphate phase-II
