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Product identity

Chemical name Ammonium polyphosphate
CAS 68333-79-9
ECN 269-789-9
ISO 51

Regulatory status

H phrases according to GHS Labelling none
REACH Regsitered 2010

Suppliers / trade names (pinfa member companies)

Supplier Trade name
ThorAFLAMMIT® PCI 202More Info
ThorAFLAMMIT® PCI 202More Info
ClariantExolit® AP 42xMore Info
BudenheimFR CROS®More Info

Application groups

Group Substrate Application
Solid ThermoplasticsPolypropylene (PP)Applicable
Polyethylene (PE)Applicable
Themoplastic elastomersCould be applied
FoamsRubbers/elastomersCould be applied
PUR flexible foamApplicable
PUR rigid foamApplicable
Textiles/Paints/AdhesivesOther textile fibersApplicable
Intumescent coatingsApplicable
Latex/adhesivesCould be applied
Textile back coatingCould be applied
ThermosetsAcrylic resinsApplicable
Epoxy resinsApplicable
Phenolic resinsApplicable
Unsaturated polyestersApplicable
Vinyl estersCould be applied
OthersPaper/woodCould be applied


Ammonium polyphosphate is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching. The properties of ammonium polyphosphate depend on the number of monomers in each molecule and to a degree on how often it branches. Shorter chains (n < 100) are more water sensitive and less thermally stable than longer chains (n > 1000)[1]. Consequently, short polymer chains and oligomers (e.g. pyro-, tripoly-, and tetrapoly-) are more soluble and show decreasing solubility with increasing chain length.[2]

Ammonium polyphosphate (APP) is used as a flame retardant in many applications such as paints and coatings, and in a variety of polymers: the most important ones are polyolefins, and particularly polypropylene, where APP is part of intumescent systems.[6] Compounding with APP-based flame retardants in polypropylene is described in.[7] Further applications are thermosets, where APP is used in unsaturated polyesters and gel coats (APP blends with synergists), epoxies and polyurethane castings (intumescent systems).

Ammonium polyphosphates as used as flame retardants in polymers have long chains and a specific crystallinity (Form II). They start to decompose at 240 °C to form ammonia and polyphosphoric acid. The phosphoric acid acts as a catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood. The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate esters. The esters decompose to release carbon dioxide and regenerate the phosphoric acid catalyst. In the gas phase, the release of non-flammable carbon dioxide helps to dilute the oxygen of the air and flammable decomposition products of the material that is burning. In the condensed phase, the resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat therefore preventing the pyrolysis of the substrate.[8] Use as an intumescent is achieved when combined with polyalcohols such as pentaerythritol and melamine as expanding agent. The mechanisms of intumescence and the mode of action of APP are described in a series of publications.[9][10] Due to its uncritical toxicological and environmental profile, ammonium polyphosphate has the potential to widely substitute halogen-containing flame retardants in a series of applications like flexible and rigid PUR-foam and thermoplastics.


1. Wikipedia entry

2. GreenScreen Assessment on GreenScreen® Store

3. Clariant EcoTain Label for ammonium polyphosphate products: see tab “EcoTain” in the product datasheet here

4. ENFIRO research project funded by the European Commission (2013): video, final report, website

5. US Environment Protection Agency Design for Environment projects on Alternatives to brominated Flame Retardants

a) An Alternatives Assessment for the Flame-Retardant Decabromodiphenyl Ether (DecaBDE) (2014)

b) 2015 Update of Report on Flame Retardants Used in Flexible Polyurethane Foam: Final Report Sections

6. US-EPA Provisional Peer-Reviewed Toxicity Values for Ammonium polyphosphate

7. US National Research Council (2000) Toxicological Risks of Selected Flame-Retardant Chemicals

8. Umweltbundesamt (2000): Erarbeitung von Bewertungsgrundlagen zur Substitution umweltrelevanter Flammschutzmittel (in German)

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