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Exolit® AP 418 (TP)

Halogen-free Exolit AP 418 (TP), especially designed for solvent-based intumescent coatings

Edition Date :
July 18, 2022

Halogen-free Exolit AP 418 (TP), especially designed for solvent-based intumescent coatings, offers longer fire resistance time (FRT) compared to conventional solutions by exhibiting an earlier on-set temperature. Therefore, a lower dry film thickness (DFT) for achieving the desired FRT is required compared to standard formulations. In addition, the protection of combustible and heat sensitive substrates is improved. Clariant’s well-known ammonium polyphosphate offers the consistent quality to produce and offer a stable intumescent coating. 

Exolit AP 418 (TP) is a free flowing white powder with low solubility in water. Additionally, it is completely insoluble in organic solvents. The product is non-hygroscopic and non-flammable.


  • Non-halogenated flame retardant with favorable environmental and health profile
  • “Fire protection at low temperature” even for sensitive carrier matrices due to early start reaction by using Exolit AP 418 (TP). Even heat sensitive substrates can be flame protected by coating formulations with Exolit AP 418 (TP) e.g. plastic materials, textiles, composite materials and others
  • Earlier start reaction of formulations with Exolit AP 418 (TP) enhances heat protecting properties of solvent-based intumescent coatings by prolonging the fire resistant time
  • More efficient fire protection performance safes energies and resources and supports a light-weight steel construction
  • Less application steps might be required to achieve comparable fire protection ratings
  • The superior fire protection at low temperatures enables the application on heat-sensitive and/or flammable substrates like:

Thin-sheet metal surfaces (e.g. like aluminum)
Plastic materials
Composite materials (Carbon- or glass-fiber reinforced materials, WPC…)


  • Particularly suitable as an ”acid donor” for intumescent coatings thanks to its low water solubility
  • Steel structures coated with intumescent paints can meet the requirements of fire resistance classes specified in ASTM, BS, DIN, GB, EN, UL and others
  • The application on wood or plastics enables these materials to qualify for Building Material Class B (DIN EN 13501-1)
  • Excellent flame-retardant effect in cellulose-containing materials such as paper and wood products. With chipboard products, the DIN EN 13501-1 classification can be achieved by adding 15 - 20 % Exolit AP 418 (TP)
  • Imparts a good flame-retardant effect to adhesives and sealants when it is incorporated into the base formulation at the rate of 10 - 20%
  • Suitable non-halogenated flame retardant for polyurethane foams. PUR foams with Exolit AP 418 (TP) can be recycled
  • In the case of thermosets like epoxy resins and unsaturated polyester resins, it paves the way for the production of lightweight components with low solids content
  • Can be used in transport applications to obtain good fire, smoke and toxicity results (EN 45545)
  • (Bio-)degradable by breaking down to naturally occurring phosphate and ammonia


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For regulatory details such as the classification and labeling as dangerous substances or goods please refer to our corresponding material safety data sheet.Minimum shelf life is 12 months from the date of shipping when stored according to the said conditions.

Exolit AP 418 (TP) is packed in 40 x 25 kg-paper bags (polyethylene inliner) net per 1.000 kg pallet, shrink wrapped.
Also available in 500 kg and 1.000 kg big bags net per 1.000 kg pallet, shrink wrapped. 




 Chemical Formula    [NH4PO3]n - x  
 Phosphorus  % (w/w)  31-32 - x  Photometry after oxidizing dissolution; (11/17)
 Water/Moisture  % (w/w)  max. 0.3 x -  Thermogravimetry at 130 °C; (11/03)
 Nitrogen  % (w/w) 14-15  x  Elemental analysis; (11/07)
 Bulk Density  g/cm3  approx 1.9  
 pH Value    4-7 x - Potentiometry in 10 % aqueous suspension; (11/12)
 Solubility in Water  % (w/w) max. 1.5 x Gravimetry after filtration of a 10 % aqueous suspension at 25 °C; (11/41)
 Average Particle Size (D50) µm    approx 15  Laser diffraction
 Particle Size Distribution  % (w/w)   x  Air jet sieving; (11/02)
   > 100 µm  max. 0.2      

¹) Delivery specification: The product is constantly monitored to ensure that it adheres to the specified values. Test methods: Clariant method numbers 11/xx in brackets.
²) Technical data: The technical data are used solely to describe the product and are not subject to regular monitoring. 


Exolit AP 418 (TP) can be used for all applications ammonium polyphosphate is suitable for. In cases where a specific phosphorus content is required to obtain the desired effect, the lower phosphorus content of Exolit AP 418 (TP) should be compensated by increasing the amount of product added.

Exolit AP 418 (TP) can be used advantageously in intumescent coatings where the ammonium polyphosphate is required to have low water solubility and where lower heat stability at temperatures above 300 °C contributes to more rapid foaming of the coating. 

Intumescent coatings
On account of its low water solubility, Exolit AP 418 (TP) is particularly suitable as an ”acid donor” for intumescent coatings. Other essential components of intumescent systems include a binder, a carbon donor (e.g. pentaerythritol) and a blowing agent (e.g. melamine).
On exposure to flame, the intumescent coatings form a carbonaceous foam which effectively shields the underlying material from temperature increases. 

Polyurethane foams
Exolit AP 418 (TP) is a suitable non-halogenated flame retardant for polyurethane foams. If handling of Exolit AP 418 (TP) as a solid is not possible we recommend the dosage of the flame retardant by preparing an Exolit AP 418 (TP)/polyol-suspension. To prevent the solid from settling the Exolit AP 418 (TP) suspensions should be stirred or circulated by pump.  

Other applications
Exolit AP 418 (TP) has an excellent flame-retardant effect in cellulose-containing materials such as paper and wood products. With chipboard products the B classification according to DIN EN 13501-1 can be achieved by adding 15 - 20 % Exolit AP 418 (TP). Casting resins based on epoxy resins or unsaturated polyester resins achieve the classification UL94-V0 with Exolit AP 418 (TP).

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