- ▸ Intumescent coatings: Acid source in intumescent fire-protective coatings.
- ▸ Flame-retardant plastics: Halogen-free flame retardant for polymers.
- ▸ Liquid fertilizer: Phosphorus and nitrogen source for crops.
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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Ammonium polyphosphate (APP) is the halogen-free acid source and backbone of intumescent flame retardancy — combined with a carbon source and a blowing agent it builds the expanding, insulating char that protects the substrate. Identity: CAS 68333-79-9.
What it is
Ammonium polyphosphate (CAS 68333-79-9, (NH4PO3)n) is a white powder inorganic polymer. It is the central component of most halogen-free intumescent systems, supplied in grades that differ in chain length and water resistance.
How it performs in fire
On heating, APP releases polyphosphoric acid (the acid source) that dehydrates a carbon source such as pentaerythritol into char, while a nitrogen source such as melamine releases gas that blows the char into a thick, insulating intumescent layer. The layer shields the polymer and starves the flame. Crystal phase I grades have shorter chains and higher water solubility; phase II (and microencapsulated/coated) grades have long chains and high water resistance for durable applications.
Applications
APP is used in intumescent fire-protective coatings, halogen-free flame-retardant polyolefins, thermosets, and textile and paper treatments, with a carbon source and a nitrogen source. See the intumescent system in the flame retardants guide; synergizes with expandable graphite.
Forms, grades and handling
APP is supplied as a white powder in phase I and phase II (and coated/microencapsulated) grades in bags and bulk. Properties are typical reference values; the Certificate of Analysis (CoA) for the lot you buy governs. Handle per the current Safety Data Sheet (SDS), and confirm regulatory status and restrictions for your market and end use. Each lot ships with CoA, TDS and SDS.
Bulk supply and RFQ
RawSource sources Ammonium Polyphosphate direct from producers in bulk, with CoA, TDS and SDS per lot. Tell us your polymer or system, the fire test you must pass, your maximum loading, and any particle-size or grade requirement, and we will quote the right grade. See the full range and selection logic in the flame retardants guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical / class | Flame retardant (intumescent acid source) |
| Flame-retardant type | Intumescent acid source (halogen-free) |
| Role in fire performance | Acid source of intumescent char |
| CAS Number | 68333-79-9 |
| Molecular Formula | (NH4PO3)n |
| Handling | Refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 269-789-9
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Solutions Using This Product
Process-solution guides on this site that specify this chemistry:
- Flame Retardants for Plastics & Polymers (Plastics & Polymers)
- Flame Retardants for Textiles: APP, Mineral & N-P Systems (Textiles)
- Intumescent & Fireproofing Coating Additives (Coatings & Construction)
Frequently Asked Questions
What is ammonium polyphosphate (APP) used for?
Ammonium polyphosphate (APP, CAS 68333-79-9) is the halogen-free acid source and backbone of intumescent flame retardants, used in intumescent coatings, halogen-free polyolefins and thermosets, and textile treatments, with a carbon source (pentaerythritol) and a nitrogen source (melamine).
What is the difference between phase I and phase II APP?
Phase I APP has shorter chains and higher water solubility (lower cost, less durable); phase II APP has long chains and high water resistance, and is often coated or microencapsulated for durable and outdoor applications.
How is bulk ammonium polyphosphate supplied and quoted?
RawSource supplies ammonium polyphosphate in bulk with CoA, TDS and SDS per lot. Pricing is quote-based on grade, particle size and volume; submit an RFQ with your polymer/system and the fire test you must pass.
What is the REACH and TSCA regulatory status of Ammonium Polyphosphate (APP)?
Ammonium Polyphosphate (APP) (CAS 68333-79-9) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 269-789-9).