What is Ammonium Polyphosphate APP CAS 68333-79-9?

Ammonium Polyphosphate, abbreviated APP, CAS 68333-79-9, is an inorganic polymeric ammonium salt of polyphosphoric acid with the general formula (NH4PO3)n. It is a halogen-free flame retardant used mainly in intumescent systems to promote char formation and suppress flame spread.

What is the difference between APP Phase I and APP Phase II?

APP Phase I has a short linear chain, usually with n below 100, so it is more water-sensitive and less thermally stable. APP Phase II has a high polymerization degree, typically n above 1000, with a branched or cross-linked structure, lower water solubility, and decomposition onset around 300 C, making it better for long-term water and humidity resistance.

How does Ammonium Polyphosphate work as a flame retardant?

In intumescent flame-retardant systems, APP acts mainly as an acid source and char promoter. When heated, it releases phosphoric acid, which reacts with carbon sources to dehydrate them and form a swollen, protective carbonaceous char layer that insulates the underlying material.

What are the typical specifications for APP Phase II industrial grade?

A common APP Phase II grade is white powder with phosphorus content around 31-32%, nitrogen around 14-15%, pH 5.5-7.5 in a 10% suspension, low water solubility below about 0.5 g/100 mL at 25 C, and thermal decomposition onset above about 285-300 C. Exact limits vary by grade, so the supplier COA remains the controlling specification.

What are the main applications of Ammonium Polyphosphate?

APP is used in halogen-free intumescent coatings for steel structures, wood and building materials, and in flame-retardant compounds for PP, PE, EVA and other polymers. It is also used in adhesives, sealants, textiles, cables and some rigid polyurethane systems where low smoke and char protection are required.

Ammonium Polyphosphate (APP) CAS 68333-79-9

Ammonium Polyphosphate (CAS 68333-79-9), commonly abbreviated as APP, is a highly efficient inorganic polymer utilizing its high phosphorus and nitrogen content to function as a premier halogen-free flame retardant. Chemically identified as the ammonium salt of polyphosphoric acid, this white, free-flowing powder acts through an intumescent mechanism; upon exposure to heat, it decomposes to release non-combustible gases and forms a thick, insulating carbonaceous char layer (foam) that cuts off oxygen and heat from the substrate. In intumescent formulations, Pentaerythritol is a related carbon-source component; actual loading and processing should be qualified as a full system. It is commercially available in different crystal phases, with Phase II (High Polymerization, n>1000) being the industry standard for solvent-based intumescent coatings, thermoplastics (PP, PE), and polyurethane foams due to its low water solubility and high thermal stability. We ensure bulk supply capabilities for this material, providing access to competitive factory pricing and customized specifications to meet specific requirements, such as Silane Surface Treatment (to improve water resistance and compatibility) or Melamine-modified grades. Full technical documentation, including MSDS, TDS, COA, is available to support compliance and safety protocols.

CAS: 68333-79-9
Synonyms: APP, APP Phase II, Polyphosphoric acids ammonium salts, Ammonium polyphosphate flame retardant, APP Intumescent
Einecs: 269-789-9
Molecular Formula: (NH₄PO₃)ₙ
Grade: Industrial Grade
Package: 25 kg bag (standard); 500 kg / 1000 kg big bag optional

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Product Description

APP is an inorganic polymeric phosphate salt containing both phosphorus and nitrogen. In intumescent flame-retardant (IFR) formulations, it acts as an acid source and char promoter, supporting the formation of a protective expanded carbonaceous layer under fire exposure. High-polymerization APP (often Phase II) is preferred when water resistance, thermal stability, and migration resistance are important.

1 Physicochemical Properties

2 Applications

3 Storage Conditions

4 Safety Precautions

Physicochemical Properties

Typical values for industrial APP Phase II; final COA values are batch-dependent.

Item	Typical Specification
Appearance	White powder / granular powder
CAS	68333-79-9
EC (EINECS)	269-789-9
Polymerization degree	n > 1000 (Phase II, typical)
Phosphorus content (P, wt.%)	~29–31% (typical market grade)
Nitrogen content (N, wt.%)	~13–15% (typical market grade)
pH (10% suspension)	~6.0–8.0 (typical)
Water solubility (25°C)	Low for Phase II (recommended for water-resistant IFR systems)
Decomposition onset	~300°C (Phase II, typical)
Density (approx.)	~1.9 g/cm³ (typical)

Applications

Intumescent flame-retardant coatings (IFR) for steel structures, wood, and building materials
Plastics & polymers: PP, PE, EVA and compatible systems (often used with carbon source & blowing agent)
PU foams / sealants (formulation-dependent; compatibility test recommended)
Rubber, adhesives, and composite materials requiring halogen-free flame retardancy
Construction boards & panels where char-forming performance is desired

For related flame-retardant additives, see Zinc Borate and Melamine Cyanurate.

Storage Conditions

Store in cool, dry, well-ventilated warehouse; keep containers tightly sealed.
Protect from moisture (powder may cake if exposed to humidity).
Keep away from strong oxidizers and sources of contamination.
Recommended storage temperature: ambient; avoid prolonged direct sunlight.
Shelf life: typically 12–24 months under proper storage (depends on packaging & humidity control).

Safety Precautions

Avoid dust inhalation; use local ventilation and dust mask/respirator if needed.
Wear safety goggles and protective gloves; wash hands after handling.
May cause skin/eye irritation; seek medical advice if symptoms persist.
Clean spills promptly to prevent slipping and dust dispersion; dispose according to local regulations.
SDS available upon request.

FAQ - Technical & Supply Chain

Q:
What is Ammonium Polyphosphate APP CAS 68333-79-9?

A: Ammonium Polyphosphate, abbreviated APP, CAS 68333-79-9, is an inorganic polymeric ammonium salt of polyphosphoric acid with the general formula (NH4PO3)n. It is a halogen-free flame retardant used mainly in intumescent systems to promote char formation and suppress flame spread.
Q:
What is the difference between APP Phase I and APP Phase II?

A: APP Phase I has a short linear chain, usually with n below 100, so it is more water-sensitive and less thermally stable. APP Phase II has a high polymerization degree, typically n above 1000, with a branched or cross-linked structure, lower water solubility, and decomposition onset around 300 C, making it better for long-term water and humidity resistance.
Q:
How does Ammonium Polyphosphate work as a flame retardant?

A: In intumescent flame-retardant systems, APP acts mainly as an acid source and char promoter. When heated, it releases phosphoric acid, which reacts with carbon sources to dehydrate them and form a swollen, protective carbonaceous char layer that insulates the underlying material.
Q:
What are the typical specifications for APP Phase II industrial grade?

A: A common APP Phase II grade is white powder with phosphorus content around 31-32%, nitrogen around 14-15%, pH 5.5-7.5 in a 10% suspension, low water solubility below about 0.5 g/100 mL at 25 C, and thermal decomposition onset above about 285-300 C. Exact limits vary by grade, so the supplier COA remains the controlling specification.
Q:
What are the main applications of Ammonium Polyphosphate?

A: APP is used in halogen-free intumescent coatings for steel structures, wood and building materials, and in flame-retardant compounds for PP, PE, EVA and other polymers. It is also used in adhesives, sealants, textiles, cables and some rigid polyurethane systems where low smoke and char protection are required.

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