Ammonium Polyphosphate (APP) is a widely used halogen-free flame retardant suitable for various polymer systems and intumescent coatings. It decomposes at elevated temperatures to release phosphoric acid, promoting the formation of a stable, insulating char layer that protects the substrate during fire exposure.
| Property | Typical Value |
|---|---|
| Chemical Name | Ammonium Polyphosphate |
| CAS No. | 68333-79-9 |
| Appearance | White powder |
| Phosphorus Content | ≥ 28% |
| Nitrogen Content | ≥ 14% |
| Decomposition Temperature | > 275 °C |
| Solubility in Water (25 °C) | Low (depends on polymerization degree) |
| pH (10% solution) | 5.5 – 7.0 |
| Customer Need | APP Benefit |
|---|---|
| Halogen-free product for green certifications | APP is REACH and RoHS compliant |
| Low smoke requirement in enclosed spaces | Produces minimal smoke during combustion |
| Char-forming for structural protection | Expands to form thermal insulation barrier |
| Compatibility with thermoplastics | Works well in filled and unfilled polymer systems |
Q1: What is the difference between APP Phase I and Phase II?
Phase II has a higher polymerization degree and better water resistance, making it preferred for outdoor and high-performance applications.
Q2: Can APP be used in water-based coatings?
Yes, specially modified APP grades are available for aqueous systems.
Q3: How is APP different from MCA or ATH?
APP forms char via acid-phase mechanism, while MCA works with nitrogen chemistry and ATH acts as a mineral diluent and smoke suppressor.
