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, abbreviated APP, is an inorganic polymeric phosphate flame retardant supplied for halogen-free intumescent and polymer applications. Confirm the required grade and specification, then request a quotation with COA/TDS/SDS for bulk supply.

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

Ammonium Polyphosphate, abbreviated APP, CAS 68333-79-9, is an inorganic polymeric ammonium salt of polyphosphoric acid.

Synonyms: APP; APP Phase II; Polyphosphoric acids ammonium salts; Ammonium polyphosphate flame retardant; APP Intumescent.

CAS: 68333-79-9.

It has the general formula (NH4PO3)n.

It appears as a white powder or granular powder.

It has a phosphorus content of about 29–31% and nitrogen content of about 13–15%.

APP Phase II has a high polymerization degree, typically n above 1000, with low water solubility and high thermal stability.

It acts as an acid source and char promoter in intumescent flame-retardant systems.

When heated it releases phosphoric acid, which dehydrates carbon sources to form a protective expanded char layer.

It is halogen-free and supports low-smoke, char-forming fire protection.

It is used in intumescent coatings for steel structures, wood and building materials.

It is used in flame-retardant compounds for PP, PE, EVA and other polymers.

It is used in adhesives, sealants, textiles, cables and some rigid polyurethane systems.

It is used in rubber and composite materials requiring halogen-free flame retardancy.

Confirm appearance, polymerization degree, phosphorus content, nitrogen content, pH, water solubility, decomposition onset and density.

Store sealed in a cool, dry, well-ventilated place, away from moisture and direct sunlight.

Confirm packaging with the requested quantity and destination requirements.

The page is an RFQ entry point and does not state stock, price, MOQ or fixed lead time.

For an RFQ, state the intended use, required grade and specification, quantity, packaging, destination and document needs.

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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