|Chemical name||Ammonium polyphosphate (with synergists)|
|H phrases according to GHS Labelling||none|
Suppliers / trade names (pinfa member companies)
|Thor||Aflammit® PPN range|
|Clariant||Exolit® AP 7xx|
|Foams||PUR flexible foam||Applicable|
|PUR Rigid foam||Applicable|
|Rubbers/Elastomers||Could be applied|
|Hot melts||Could be applied|
|Latex/adhesives||Could be applied|
|Vinyl esters||Could be applied|
|Acrylic resins||Could be applied|
|Wire and cables||PE/EVA||Applicable|
|Others||Paper/Wood||Could be applied|
When ammonium polyphosphate is combined with other suitable chemical ingredients, the fire retardant effect in the matrix and/or processability during the manufacturing process can be greatly improved.
For example, when combined with polyol-components and spumific (foaming) agents (e.g. melamine and its derivatives) an intumescent system can be formed. The addition of inorganic additives can further improve the char stability. The resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat therefore preventing the pyrolysis of the substrate.
Combination with gas-phase active flame retardants
Besides the dilution of flammable gases by emitting ammonia and promoting the dehydration of the polymer matrix, ammonium polyphosphate is mostly active in the condensed phase. Therefore, the combination with a gas-phase active flame retardants can be beneficial to prohibit radical chain reactions of emitted pyrolysis gases. Examples for those species are phosphinates, inorganic hypophosphites, DOPO(-derivatives) and red phosphorus.
Combination with ablative flame retardants
While APP promotes the generation of water due to its own acidity, this effect can be enhanced by the combination with ablative flame retardants. Widely used components are metal hydroxides and oxides like ATH, MDH, boehmite, ZnO, B2O3 etc.). The hydroxy components react with protons to release water in an early state. However, the metals remain in the char and form highly temperature stable (pyro)phosphates increasing the char stability and therefore protecting the underlying polymer matrix more efficiently.
Combination with processing agents
The processability of polymers is of high importance to achieve a maximum in throughput and time-efficiency, striving to an optimized cost-efficiency. It is obvious that certain filler-type materials like ammonium polyphosphate can aggravate and in the worst case prohibit the manufacturing process of FR-equipped matrices.
To overcome processing issues, like reduced throughput, worse mechanical stability, reduced processing temperatures etc., ammonium polyphosphate can be coated and/or combined with suitable processing aids.
Salmeia KA, Fage J, Liang S, Gaan S: An Overview of Mode of Action and Analytical Methods for Evaluation of Gas Phase Activities of Flame Retardants, Polymers 2015, 7, 504-526; doi:10.3390/polym7030504