Exolit® AP non-halogenated flame retardants – making polyurethanes safer


The Exolit® AP products are phosphorus-based flame retardants for polyurethanes that allow meeting stringent emission and migration requirements, because they are inorganic solids with low vapor pressure and solubility. Furthermore stringent fire safety standards such as the FMVSS 302 (SE), EN 13501-1 (E) or DIN 4102 (B2) can be passed.


Exolit® AP non-halogenated flame retardants are safer and more sustainable alternatives to volatile and scrutinized flame retardants such as halogenated and non-halogenated phosphate esters (e. g. TCPP1). They are based on high molecular weight ammonium polyphosphate (phase II). Because of lower solubility in water, catalyst interaction is reduced. They can be used on their own in synergistic combinations. Clariant sells the pure ammonium polyphosphate (e.g. Exolit AP 422) as well as a ready-to-use synergistic blend, Exolit AP 750. Exolit AP 422 has shown to be less abrasive to PUR dosing and metering equipment than many other common solid fillers in trials with renowned equipment manufacturers. Thanks to microencapsulation, Exolit AP 462 is even less susceptible to reaction with amine catalysts, and easily dispersible in typical polyester polyols.

Lower fogging and VOC values can be achieved which meet stringent emission standards for PUR flexible foams in the automotive industry. PUR producers are facing demanding regulations regarding the emission of volatile organic compounds (VOC)2. Furthermore, due to regulatory scrutiny several phosphate esters might be banned from usage in various products in the near future.3 With respect to this need, Exolit AP products are an excellent choice. Being non-hazardous, inorganic substances, Exolit AP products pose no additional risk to health and environment, and do not contribute to harmful VOC emissions.

The Exolit® product family was the pioneer in non-halogenated flame retardants that could withstand the demanding requirements of different high end segments for plastics.

Rigid PUR and PIR for insulation containing Exolit AP can pass DIN 4102 (B2) or EN 13501-1 (E). Flexible PUR for automotive slabstock can pass FMVSS 302 (SE).

Exolit AP products show a favorable environmental and health profile compared to TCPP with negligible plasticizing effect, reduced influence on mechanical properties and higher system-stability compared to other APP grades.

Exolit AP is non hazardous, studies on life cycle data are available. It has been awarded the EcoTain label - Clariant's approach to highlight sustainable products. Ammonium polyphosphate (CAS No. 68333-79-9), the basic ingredient in Clariant’s Exolit AP product range, is also assigned a GreenScreen Benchmark™ of 34.

1) Tris(1-chloro-2-propyl)phosphate, CAS No. 13674-84-5

2) See e. g. in China (GB/T 27630-201X)

3) See e. g. GADS list, http://www.gadsl.org/, or CORAP list, https://echa.europa.eu/information-on-chemicals/evaluation/community-rolling-action-plan/

4) See https://www.greenscreenchemicals.org/gs-assessments/chemical/68333-79-9

Possible replacement to

TCPP (Tris(1-chloro-2-propyl)phosphate) CAS No. 13674-84-5; TCEP (Tris(2-chloroethyl)phosphate) CAS No. 115-96-8; TDCPP (Tris(1,3-dichloro-2-propyl)phosphate) CAS No. 13674-87-8; DecaBDE (Decabromodiphenyl ether) CAS No. 1163-19-5