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Product identity

Chemical name Aluminium monohydrate (Boehmite)
CAS 1318-23-6
ECN 215-284-3

Regulatory status

H phrases according to GHS Labelling none
REACH Regsitered 2010

Suppliers / trade names (pinfa member companies)

Supplier Trade name
Nabaltec AGACTILOX® and APYRAL® AOHMore Info

Application groups

Group Substrate Application
Solid ThermoplasticsPolyethylene (PE)Applicable
PVC rigidApplicable
Themoplastic elastomersApplicable
Polycarbonate (PC)Could be applied
Polyamide (PA)Applicable
Polypropylene (PP)Applicable
FoamsPUR flexible foamApplicable
PUR rigid foamApplicable
Polyethylene foam (PE)Applicable
PVC/nitrile foamApplicable
Polypropylene foam (PP)Applicable
Hot meltsApplicable
ThermosetsEpoxy resinsApplicable
Phenolic resinsApplicable
Unsaturated polyestersApplicable
Vinyl estersApplicable
Acrylic resinsApplicable
Wire and cablesPE/EVAApplicable
PVC flexible & rigidApplicable
Polypropylene (PP)Applicable


Aluminium monohydrate (AOH) – also called Boehmite – is hydrated aluminium. It is a fine, white, highly pure, inorganic crystalline powder. Compared to Aluminium Tri Hydrate (ATH), which starts to decompose at 200°C, the decomposition of Boehmite starts only from 340 °C upward. With 17 wt.-% AOH also has a significantly lower loss on ignition than ATH (34.6 wt.-%).
Likewise ATH, the working principle as a flame retardant is based on the thermal decomposition of Boehmite into aluminium oxide and water. The generated water vapour cools the polymer surface, dilutes the concentration of burnable gases in the surroundings and the oxide layer acts as a barrier protecting the polymer against further decomposition. The remaining aluminium oxide residue has a high internal surface where sooty particles, respectively polycyclic aromatic hydrocarbons, are absorbed, making AOH also a smoke suppressant. But due to the lower amount of crystal bound water the endothermic reaction in case AOH consumes less energy from the ignition source compared to ATH. In summary, AOH has a much wider processing window caused by its high decomposition temperature, but has a lower flame retardant efficiency per mass. Hence, AOH is rarely used as a sole flame retardant (FR). But combined with other FR, e.g. phosphorous and nitrogen based FR, remarkable synergistic effects have been reported in polyamide and polyesters.
AOH is commercially available in grain sizes ranging from 0.3 – 3 µm in median particle size (D50). AOH has an extremely low electrolyte content. This low electrolyte content is also an important influencing factor regarding resin viscosity and resins hardening and makes AOH ideal for utilization in electrically insulating plastic products, e.g. PCB laminates or cast resins.
Beside this, AOH acts as an acid scavenger. It can capture aggressive by-products formed during processing of phosphorous containing FR, to avoid corrosion of e.g. compounding and injection moulded screws.

By a comprehensive set of toxicological data performed under the REACH regulation (ECHA, EU) Boehmite has been proven as a non-hazardous and non-classified substance. Due to this favourable environmental and health profile Boehmite is a very good alternative for a wide range of application.


1. Alexander B. et al. “Non-halogenated Flame Retardant Handbook”, Scrivener Publishing LLC., USA (2014), ISBN 978-1-118-68624-9.
2. pinfa brochure: “Flame Retardants in Electric & Electronic Applications”, Non-halogenated phosphorus, inorganic and nitrogen flame retardants (October 2017, 3rd edition).
3. pinfa brochure: “Innovative and Sustainable Flame Retardants in Transportation”, Non-halogenated phosphorus, inorganic and nitrogen flame retardants (2017).
4. www-entry
5. Wikipedia entry (15-04-2021).
6. Wikipedia entry (15-04-2021).
7. Nabaltec AG, Brochure: “Flame retardants for engineering plastics” (08/2020).
8. Nabaltec AG, Brochure: “Metal hydrates for cables” (06/2020).
9. Nabaltec AG, Brochure: “Metal hydrates for elastomers” (06/2020).
10. Nabaltec AG, Brochure: “Metal hydrates for PVC” (06/2020).
11. Nabaltec AG, Brochure: “Metal hydrates for thermosets” (01/2021).
12. Nabaltec AG, Brochure: “Mineral based flame retardancy with metal hydrates” (06/2020).

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