Boehmite (aluminium oxide hydroxide, AlO(OH), CAS 1318-23-6) is a mineral flame retardant and functional filler for plastics, used where aluminum trihydrate (ATH) decomposes too early in the process. Because boehmite carries one hydroxyl group per aluminium atom instead of three, it holds its water to a higher temperature than ATH, which raises the question of what that costs in flame-retardant effect.
Boehmite is registered under REACH, Regulation (EC) No 1907/2006, under EC number 215-284-3, has never been placed on the REACH Candidate List, is not restricted under the RoHS Directive and is not listed under the EU POPs Regulation (EU) 2019/1021, status 23 September 2026. Boehmite is one of 437 substances in our directory of plastic additives, each carrying the same identity, dosage and regulatory fields.
This page holds the plastics view of a substance the search results still describe as bauxite ore: the identity that separates boehmite from gibbsite and alumina, the dehydration mechanism, the physical constants, the polymers, applications and test methods, a four-mineral comparison with ATH, MDH and huntite-hydromagnesite, a dated regulatory matrix, the producers a buyer can source, and a record of every number the industry has not published.
Table T1. Boehmite identity card.
| Field | Value |
|---|---|
| Name | aluminium oxide hydroxide (boehmite) |
| Abbreviation | AlOOH |
| CAS number | 1318-23-6 |
| EC number | 215-284-3 |
| Molecular formula | AlO(OH) |
| Molecular weight | 59.99 g/mol |
| Chemical class | metal oxyhydroxide (mineral flame retardant) |
| Function | high-temperature mineral flame retardant and functional filler |
| Synonyms | aluminium oxyhydroxide, aluminum monohydrate, gamma-AlO(OH), gamma-AlOOH, böhmite |
| Trade names | Apyral AOH (Nabaltec), Actilox (Nabaltec) |
| REACH | registered (ECHA CHEM, EC 215-284-3) |
| REACH Candidate List (SVHC) | no |
| Halogen content | none |
Footnote: identity and molecular data from PubChem CID 73982; EC number from ECHA CHEM 100.013.896; mineral property data from the boehmite mineral record. Status as of 23 September 2026.
What Is Boehmite (AlOOH)?#
Boehmite is the gamma form of aluminium oxide hydroxide, AlO(OH), a white mineral powder with a molecular weight of 59.99 g/mol that the plastics industry uses as a halogen-free flame retardant and functional filler. PubChem records the substance as CID 73982 under CAS 1318-23-6, and the same material travels under five other names on a data sheet: aluminium oxyhydroxide, aluminium monohydrate, gamma-AlO(OH), gamma-AlOOH and the German spelling böhmite. Its chemical class is metal oxyhydroxide, which places it beside the metal hydroxides rather than among the organic flame retardants. Which material, then, does the name boehmite actually cover in a compound formulation?
Mineral flame retardants for plastics are defined by what they release: ATH, magnesium hydroxide, boehmite and huntite-hydromagnesite all carry bound water or carbonate that a fire drives off. Boehmite belongs to the mineral branch of the flame retardants for plastics family, the halogen-free additives that work by absorbing heat instead of interrupting the flame chemistry. One caveat belongs in the definition itself: our source library records no production route for boehmite, so this page describes what the mineral is and does, not how a given grade is made.
What does the formula AlO(OH) mean?#
AlO(OH) means one aluminium atom carrying one oxygen atom and one hydroxyl group, which is why boehmite is also called aluminium monohydrate: ATH, Al(OH)3, carries three hydroxyl groups on the same aluminium atom. That single structural difference sets the molecular weights apart, 59.99 g/mol for boehmite against 78.00 g/mol for ATH, and it is the reason the two minerals hold and give up their bound water at different temperatures. How much water each one carries, and at what temperature it leaves, is what the mechanism section addresses.
Boehmite vs gibbsite and ATH: what is the difference?#
Boehmite and gibbsite are two different aluminium minerals: gibbsite is Al(OH)3, the mineral form of aluminum trihydrate (ATH), while boehmite is AlO(OH), and alumina, Al2O3, is what both of them leave behind after they have released their water. Gibbsite is the mineral form of aluminum trihydrate (ATH), the mineral flame retardant boehmite is measured against, registered under CAS 21645-51-2 and EC 244-492-7. ATH decomposes from about 200 °C (392 °F) with a theoretical loss on ignition of 34.6 % and a density of 2.42 g/cm3 (Huber Advanced Materials). Boehmite is the denser and harder of the two, at a mineral specific gravity of 3.00 to 3.07 and Mohs 3 to 3.5 against ATH's Mohs 2.5 to 3.5.
The three aluminium materials a formulator meets under similar names differ in bound water, and therefore in role.
| Material | Formula | Molecular weight | Bound water released on heating | Role in plastics |
|---|---|---|---|---|
| Boehmite | AlO(OH) | 59.99 g/mol | lower than ATH; no primary value in our source library | high-temperature mineral flame retardant and filler |
| Gibbsite / ATH | Al(OH)3 | 78.00 g/mol | 34.6 % theoretical loss on ignition | standard mineral flame retardant |
| Alumina | Al2O3 | not recorded | none; it is the residue | the residue itself, and a functional filler |
The alumina both minerals leave behind is itself a filler, covered under thermally conductive fillers.
Is boehmite a flame retardant or a filler?#
Boehmite is both: it is an additive flame retardant that is blended into the polymer rather than built into its backbone, and it is a functional filler, a mineral chosen for what it does in a fire rather than for the volume it fills. Additive flame retardants stay in the compound as free particles, unlike reactive ones such as TBBPA in an epoxy resin, which join the polymer chain. Boehmite sits with ATH, MDH and huntite-hydromagnesite among the mineral flame retardants, all of which act as functional fillers.
A mineral chosen for what it does rather than for the volume it fills is a functional filler, one of the categories on fillers for plastics, and at flame-retardant loadings its mechanical and rheological consequences are those of any high filler content.
How Does Boehmite Work as a Flame Retardant?#
Boehmite flame-retards a plastic by dehydrating endothermically: it absorbs heat from the decomposing polymer, releases its bound water as steam that dilutes the flammable gases, and leaves an alumina residue that shields the surface. The reference point is ATH, whose reaction 2Al(OH)3 to Al2O3 plus 3H2O runs from about 200 °C (392 °F) and absorbs 1051 J/g (Huber Advanced Materials cable-industry literature). Boehmite runs the analogous reaction from AlO(OH) to alumina and water. How much cooling does a mineral carrying one hydroxyl group per aluminium atom deliver?
Boehmite starts to decompose at a higher temperature than ATH and releases less water, so it survives hotter processes but delivers less cooling per kilogram. Our source library holds no primary decomposition temperature and no loss-on-ignition figure for boehmite, so this page states the direction and publishes no value.
Mineral flame retardants act in 4 ways, and boehmite uses all of them.
- Endothermic cooling: the dehydration absorbs heat and slows the supply of volatile fuel.
- Water vapour dilution: the released steam displaces oxygen and dilutes the flammable decomposition gases.
- Oxide barrier layer: the alumina residue insulates the substrate and blocks mass transfer.
- Soot adsorption and smoke suppression: the oxide residue adsorbs soot precursors, so mineral flame retardants also reduce smoke.
Gas-phase and condensed-phase action are compared on how flame retardants work; the mineral route is condensed-phase throughout. In a cone calorimeter at 35 kW/m2, an unfilled EVA/LLDPE compound ignites at about 80 s with a peak heat release rate above 550 kW/m2, and ATH or MDH delay ignition by 120 to 160 s (Huber Advanced Materials). Those times belong to ATH and MDH, not to boehmite.
What Are the Physical and Chemical Properties of Boehmite?#
Boehmite is a white powder with a mineral specific gravity of 3.00 to 3.07 and a Mohs hardness of 3 to 3.5, which makes it denser and harder than ATH (2.42 g/cm3, Mohs 2.5 to 3.5). The property set below is short on purpose: it lists the values recorded against CAS 1318-23-6 and omits every attribute that would have to come from a single supplier data sheet.
Table T2. Boehmite physical and chemical properties.
| Property | Value | Unit | Source |
|---|---|---|---|
| Appearance | white powder | - | PubChem CID 73982 |
| Molecular formula | AlO(OH) | - | PubChem CID 73982 |
| Molecular weight | 59.99 | g/mol | PubChem CID 73982 |
| Specific gravity (mineral) | 3.00 to 3.07 | - | boehmite mineral record |
| Mohs hardness | 3 to 3.5 | - | boehmite mineral record |
| Halogen content | none | - | derived from the formula AlO(OH) |
| Decomposition onset | higher than ATH's approximately 200 °C (392 °F) | °C | no primary value published |
| Loss on ignition | lower than ATH's 34.6 % | wt% | no primary value published |
Footnote: no melting point, boiling point, solubility, refractive index, pH, specific surface area or thermal conductivity is recorded for boehmite in our source library, so those rows are absent rather than estimated. The density figure is a mineral specific gravity, not a measured compound density.
The Mohs hardness of 3 to 3.5 has a direct consequence on the compounding line. A mineral that hard, at the loadings flame retardancy demands, abrades screws, barrel liners, die lands and gate inserts faster than ATH at Mohs 2.5 to 3.5 or MDH at Mohs 2 to 3, so tool wear belongs in the cost calculation alongside the mineral price. No wear-rate figure for boehmite exists in our source library, so this page names the consequence and publishes no number. The boehmite formula and that hardness explain why it is specified as a high-temperature filler.
Which Polymers Use Boehmite, and at What Dosage?#
Boehmite is used in polymers whose processing window sits above ATH's decomposition onset: epoxy laminates for printed circuit boards, and engineering thermoplastics such as polyamide and PBT that are compounded at 240 to 320 °C (464 to 608 °F). Published loading levels for boehmite are not available from a primary source; mineral flame retardants as a class run at 160 to 180 phr, about 61.5 wt% at 160 phr, in halogen-free cable compounds (Huber Advanced Materials) and at 60 to 65 wt% for UL 94 V-0 in thermoplastics (a patent-literature value), and boehmite is dosed in the same order of magnitude. Mineral loadings are quoted in PHR (parts per hundred resin) as often as in weight percent, and at 160 phr the two differ by a factor of more than two.
Table T3. Polymers, roles and loading status for boehmite.
| Polymer | Role of boehmite | Typical loading | Evidence |
|---|---|---|---|
| Epoxy and FR-4 laminate | halogen-free mineral filler alongside reactive TBBPA or DOPO derivatives | not published in our source library | our boehmite profile; our flame-retardant sources |
| Polyamide (PA), PBT, PET | high-temperature mineral option where the 240 to 320 °C process excludes ATH | not published in our source library | our boehmite profile; statement marked for verification |
| PVC | research-stage option | not published in our source library | our boehmite profile |
| Class reference: ATH or MDH in EVA/LLDPE cable (not boehmite) | endothermic mineral flame retardant | 160 to 180 phr, 61.5 wt% at 160 phr | Huber Advanced Materials cable brochure |
Boehmite in epoxy and FR-4 laminates#
Epoxy laminates for printed circuit boards are the clearest use for boehmite: the board has to reach UL 94 V-0 and survive lead-free soldering, so the mineral filler in it cannot be one that gives up its water at 200 °C. Lead-free reflow is the reason formulators give for that choice, a selection argument rather than a measured threshold. In an FR-4 laminate, boehmite sits beside a reactive flame retardant such as TBBPA (tetrabromobisphenol A) rather than replacing it.
Halogen-free laminates use DOPO derivatives instead, at 0.25 to 1.2 wt% phosphorus in published epoxy studies, and are specified to IEC 61249-2-21; the halogen limits of that standard are not recorded in our source library, so this page names the standard and prints no limit.
Boehmite in engineering thermoplastics (PA, PBT, PET)#
Polyamide and PBT are compounded at 240 to 320 °C (464 to 608 °F), far above ATH's decomposition onset, which is why the aluminium mineral used in them is boehmite rather than ATH. The full stabilizer and flame-retardant package for PA6 and PA66 is on additives for nylon (polyamide).
In this window boehmite competes against a phosphorus chemistry, not another mineral. Aluminum diethylphosphinate (AlPi, DEPAL, CAS 225789-38-8) decomposes above 300 °C and reaches UL 94 V-0 at about 15 wt% in PA 6T/66 as Exolit OP 1230, per Clariant. No boehmite loading, LOI value or UL 94 result in polyamide is recorded in our source library.
Boehmite in PVC and polyolefins#
Boehmite in PVC is still a research-stage option: the minerals in commercial PVC and polyolefin cable compounds are ATH and MDH, at 160 to 180 phr and usually with 3 to 6 phr zinc borate to cut smoke and dripping. Loadings, smoke limits and cable fire tests are covered on flame retardants for wire and cable, where the processing temperature stays low enough that ATH's 200 °C onset is an advantage rather than a disqualification.
What Is Boehmite Used For in Plastics?#
In plastics, boehmite is used in 4 areas: printed circuit boards and electrical laminates, electrical and electronic housings and connectors, halogen-free compounds for construction and transport, and, outside plastics, as a coating on lithium-ion battery separators. The four areas are set out below in the order of the evidence recorded for each one.
- Printed circuit boards and electrical laminates: epoxy composites that must hold UL 94 V-0 through a lead-free reflow process.
- Electrical and electronic housings and connectors: polyamide and PBT parts where halogen-free chemistry is specified.
- Halogen-free compounds for construction and mobility: mineral-filled compounds where smoke and halogen content are limited.
- Lithium-ion battery separator coatings: a non-flame-retardant use of the same mineral, covered below the contextual border.
Printed circuit boards and electrical laminates#
Printed circuit boards are boehmite's largest plastics application: the laminate is an epoxy composite that has to hold a UL 94 V-0 rating and pass glow-wire testing after it has been through a lead-free reflow oven. The board carries a reactive flame retardant, TBBPA or a DOPO derivative, while the mineral filler adds endothermic capacity and dimensional stability. The whole additive package for a circuit board and its housing is on additives for electrical and electronics, from the laminate resin to the connector compound.
Electrical and electronic housings and connectors#
Housings, connectors and switch parts in polyamide and PBT are the second plastics market for boehmite, and regulation is pushing them towards halogen-free chemistry. The Ecodesign Regulation (EU) 2019/2021 prohibits halogenated flame retardants in the enclosures and stands of electronic displays from 1 March 2021, a scope limited to displays rather than a general ban, and it has moved specifiers towards mineral and phosphorus chemistries. Boehmite is one of the mineral options among the halogen-free flame retardants that Ecodesign rules have pushed into electronics.
Halogen-free compounds for construction and mobility#
Construction and mobility compounds reach halogen-free fire performance with mineral flame retardants, and the published loadings in those markets belong to ATH and MDH rather than to boehmite. Halogen-free low-smoke cable jackets, roofing membranes and interior parts run at 160 to 180 phr of ATH or MDH (Huber Advanced Materials, EVA/LLDPE reference formulations). The cable market those loadings come from is described on additives for wire and cable compounds. No boehmite tonnage, market share or loading in construction or transport is recorded in our source library, so its position there is not established.
How Is Boehmite Tested, and What Does It Do to Fire Performance?#
Boehmite's contribution is measured the same way as any mineral flame retardant's: a UL 94 vertical burn, a limiting oxygen index per ISO 4589-2 or ASTM D2863, a cone calorimeter run per ISO 5660-1 and, for electrical parts, a glow-wire test per IEC 60695-2-10 to -13. A V-0 result requires a single afterflame time of 10 s or less, a total of 50 s or less over ten applications, an afterglow of 30 s or less and no flaming drips igniting the cotton; V-1 and V-2 allow 30 s single and 250 s total. Those criteria are set out on UL 94 flammability ratings.
The oxygen concentration a compound needs to keep burning is measured as the limiting oxygen index (LOI), and unmodified polypropylene sits at about 17.5 % O2, the baseline a mineral loading has to raise. Peak heat release rate and time to ignition come from cone calorimeter testing. No LOI value, UL 94 rating, peak heat release rate or time to ignition for a boehmite-filled compound is recorded in our source library. The class-level numbers this page publishes, the 120 to 160 s ignition delay in an EVA/LLDPE reference at 35 kW/m2, are ATH and MDH results.
One test applies directly to boehmite: ash content per ASTM D5630 or ISO 3451, or a thermogravimetric run, verifies that the loading on the data sheet is the loading in the pellet.
Table T4. Fire-performance indicators, standards and the published status for boehmite.
| Indicator | Standard | Boehmite value | What the compound has to reach |
|---|---|---|---|
| Flammability rating | UL 94 | not published for boehmite | V-0 for laminates and E&E parts |
| Limiting oxygen index | ISO 4589-2 / ASTM D2863 | not published for boehmite | above the 17.5 % O2 of unmodified polypropylene |
| Heat release and time to ignition | ISO 5660-1 (cone calorimeter) | not published for boehmite | class reference: ATH and MDH delay ignition by 120 to 160 s in an EVA/LLDPE reference at 35 kW/m2 |
| Glow wire | IEC 60695-2-10 to -13 | not published for boehmite | E&E target set GWIT 775 °C, GWFI 960 °C |
| Mineral content | ASTM D5630 / ISO 3451 (ash) or TGA | applicable, grade-dependent | the loading declared on the compound data sheet |
How Does Boehmite Interact with Other Flame Retardants?#
Boehmite is a partner rather than a stand-alone flame retardant in most compounds: in FR-4 laminates it works beside reactive TBBPA or DOPO, in polyamide beside phosphinates, and in mineral-filled systems beside zinc borate. The 3 partner groups it appears with are listed below.
- Reactive phosphorus and bromine partners in thermosets: TBBPA, DOPO derivatives and phosphazene in FR-4 laminates, where the mineral supplies the endothermic capacity.
- Phosphinate and nitrogen synergists in engineering thermoplastics: aluminium diethylphosphinate with melamine polyphosphate in polyamide and PBT, where the mineral is secondary.
- Zinc borate and surface-treatment packages in highly filled compounds: zinc borate releases its water above 290 °C and forms a glassy borate layer that suppresses afterglow and arc tracking.
Surface treatment is the second half of the interaction question, because a compound at 60 wt% mineral has almost no unfilled polymer left to carry the strain. Vinyl-silane treatments for silane-crosslinked systems, amino-silane treatments for thermoplastics and fatty-acid coatings restore elongation at break at those loadings; they are compared on filler surface treatment. No synergy ratio, antagonism or measured boehmite blend result is recorded in our source library, so this page describes the roles and publishes no ratios. Research on hybrid flame-retardant epoxy composites containing boehmite is recorded qualitatively only.
What Is the Regulatory Status of Boehmite?#
Boehmite is registered under REACH, is not a Substance of Very High Concern, is not a restricted substance under RoHS and is not listed under the POPs Regulation, status 23 September 2026. Six of the twelve instruments below have no entry recorded, so those cells read "status being verified" rather than "not listed": an empty field is not a clearance.
Table T5. Boehmite regulatory matrix, status 23 September 2026.
| Instrument | Boehmite status | Date / reference |
|---|---|---|
| REACH registration, Regulation (EC) No 1907/2006 | registered | ECHA CHEM, EC 215-284-3; tonnage band not recorded |
| REACH Candidate List (SVHC) | not listed | checked 23 September 2026 |
| REACH Annex XIV (authorisation) | not listed | derived: Annex XIV is drawn from the Candidate List, and boehmite has never been on it |
| REACH Annex XVII (restriction) | status being verified | no entry recorded in our source library |
| EU 10/2011 (plastic food contact) | status being verified | no Annex I entry recorded in our source library |
| EU POPs Regulation (EU) 2019/1021 / Stockholm Convention | not listed | derived: every flame retardant listed under Stockholm is an organic substance (PBDEs, HBCD, decaBDE, SCCP, Dechlorane Plus, MCCP) |
| RoHS Directive | not restricted | derived from the closed restriction list: Pb, Hg, Cd, Cr(VI), PBB, PBDE and four phthalates |
| CLP Regulation (EC) No 1272/2008 | no harmonised classification recorded | the GHS field of our boehmite record is empty; this page states no classification |
| Ecodesign Regulation (EU) 2019/2021 | not affected | the restriction covers halogenated flame retardants in electronic-display enclosures from 1 March 2021; boehmite contains no halogen |
| US FDA food contact | status being verified | no entry recorded in our source library |
| US TSCA | status being verified | no entry recorded in our source library |
| California Proposition 65 | status being verified | no entry recorded in our source library |
A registration number is not a safety verdict and not a food-contact clearance. What registration does and does not mean for a buyer is explained on REACH and plastic additives.
The closed restriction list that keeps boehmite out of scope is on RoHS and plastic additives: a mineral containing none of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, polybrominated diphenyl ethers or the four listed phthalates cannot be caught by it.
Is boehmite REACH registered, and is it an SVHC?#
Yes, boehmite is registered under REACH, Regulation (EC) No 1907/2006, under EC number 215-284-3, and no, it is not a Substance of Very High Concern: it is absent from the Candidate List as of 23 September 2026. The contrast with the reactive flame retardant in the same FR-4 laminates is sharp. TBBPA has been on the SVHC Candidate List since 17 January 2023 under Article 57(a) for carcinogenicity, and it carries a harmonised Carc. 1B H350 classification from 1 September 2025 under the 21st ATP, Delegated Regulation (EU) 2024/197. Boehmite carries neither listing. No REACH tonnage band for boehmite is recorded, so none is stated.
Is boehmite allowed in food-contact plastics?#
The food-contact status of boehmite is not established on this page: it is not recorded in our source library, and we do not publish an authorisation we have not checked against Annex I of Regulation (EU) No 10/2011. The two minerals it competes with are recorded: ATH is FCM substance No 629 (Ref 34560) and magnesium hydroxide FCM substance No 396 (Ref 64640), per the Union list consolidation of 14 July 2026. Both are authorised additives in Annex I of EU 10/2011 with no specific migration limit, so the overall migration limit of 10 mg/dm2 applies. Until an Annex I entry for boehmite is confirmed, treat a food-contact application as an open question and ask the supplier for a declaration of compliance.
Is Boehmite Safe? Health, Safety and Environmental Profile#
Boehmite is not a Substance of Very High Concern, is not listed under the POPs Regulation and contains no halogen, but our source library holds no hazard classification for it, so this page does not state one. The GHS field of the boehmite record is empty, and an empty field is not the same as "not classified": no harmonised classification under the CLP Regulation (EC) No 1272/2008 is recorded. The 3 statements this page can make about boehmite's profile are listed below.
- No listing: absent from the REACH Candidate List, from Annex XIV and from Annex I of the POPs Regulation (EU) 2019/1021 as of 23 September 2026.
- No halogen: AlO(OH) contains no bromine and no chlorine, so combustion produces no hydrogen halide and no halogenated dioxin precursor.
- No class assessment covering boehmite: the EU ENFIRO project (FP7 grant 226563, concluded 2012) found good environmental and health profiles for ammonium polyphosphate, DEPAL, ATH, MDH, melamine polyphosphate, DOPO, zinc stannate and zinc hydroxystannate; boehmite was not assessed.
Boehmite is supplied as a fine powder, so the practical workplace question is dust control at weighing and feeding rather than a substance-specific toxicological one. Our source library records no LD50, no NOAEL and no occupational exposure limit for boehmite. The concerns summarised on flame retardants and human health relate to specific halogenated and organophosphorus substances, not to halogen-free minerals.
What Are the Alternatives to Boehmite?#
The 3 mineral alternatives to boehmite are aluminum trihydrate (ATH), magnesium hydroxide (MDH) and huntite-hydromagnesite, and the only one of them that survives an engineering-thermoplastic process is MDH. The four minerals differ in the temperature at which they give up their water, in how much heat they absorb and in how much of their weight they lose, and those three columns decide the selection.
Table T6. Mineral flame retardant comparison.
| Mineral | Formula | CAS | Decomposition onset | Heat absorbed | Loss on ignition | Specific gravity | Where it is used |
|---|---|---|---|---|---|---|---|
| Boehmite | AlO(OH) | 1318-23-6 | higher than ATH (no published value) | lower than ATH (no published value) | lower than ATH (no published value) | 3.00 to 3.07 | epoxy and FR-4 laminates, engineering thermoplastics |
| ATH | Al(OH)3 | 21645-51-2 | about 200 °C (Huber; PubChem lists 300 °C) | 1051 J/g | 34.6 % theoretical | 2.42 g/cm3 | LSZH/HFFR cable, flexible PVC, thermosets |
| MDH | Mg(OH)2 | 1309-42-8 (brucite 1317-43-7) | stable to about 320 °C, water release around 330 °C | 1316 J/g | 31.0 % theoretical | 2.36 g/cm3 | polypropylene, polyamide, TPO, cable |
| Huntite-hydromagnesite | Mg3Ca(CO3)4 and Mg5(CO3)4(OH)2·4H2O | 19569-21-2 / 12072-90-1 | water from about 220 °C, CO2 from about 330 °C, char about 560 °C | not published | 51 to 54 % at 1,000 °C (UltraCarb) | not published | LSZH cable, PVC |
Footnote: ATH and MDH values come from Huber Advanced Materials technical literature; the huntite-hydromagnesite values from LKAB Minerals. The boehmite values marked qualitative are not confirmed against a primary source and are therefore not given as numbers.
All four minerals are set side by side in our mineral flame retardant comparison, which carries the class-level selection logic this page applies to one substance.
Boehmite vs ATH (aluminum trihydrate)#
Boehmite is the right choice only when the process runs too hot for ATH: wherever the compound can be processed below about 200 °C (392 °F), ATH does the job with less mineral. ATH absorbs 1051 J/g and loses 34.6 % of its weight as water, a figure our source library holds for no boehmite grade.
Boehmite's specific gravity of 3.00 to 3.07 against ATH's 2.42 g/cm3 makes a boehmite-filled compound heavier at the same volume loading, and Mohs 3 to 3.5 makes it the more abrasive. Price data for boehmite is not published on this page; our plastic additive prices guides cover the additives with a traded reference price.
Boehmite vs MDH (magnesium hydroxide)#
MDH is boehmite's real competitor at high temperature: magnesium hydroxide is stable to about 320 °C (608 °F), absorbs 1316 J/g and still releases 31.0 % of its weight as water, which is far more cooling than boehmite delivers. Coated magnesium hydroxide (MDH) grades reach filling levels above 65 wt%, per Huber Advanced Materials, and the mineral processes about 110 °C higher than ATH.
Boehmite is still specified for system fit rather than cooling capacity: it is the aluminium mineral, leaving an alumina residue that suits systems built around alumina chemistry and aluminium-based surface treatments, and it is the harder and denser of the two.
Boehmite vs huntite-hydromagnesite#
Huntite-hydromagnesite releases water and then carbon dioxide in two stages and loses 51 to 54 % of its weight at 1,000 °C, which makes it a cable mineral rather than a high-temperature laminate filler like boehmite. The two-stage release begins with water from about 220 °C and continues with carbon dioxide from about 330 °C, ending in a cement-like char at about 560 °C (LKAB Minerals UltraCarb; CAS 19569-21-2 huntite, 12072-90-1 hydromagnesite). That staged release makes huntite hydromagnesite an LSZH cable and PVC mineral rather than a laminate filler.
Boehmite vs phosphorus and brominated flame retardants#
The trade-off against phosphorus and bromine chemistry is loading: a phosphinate reaches UL 94 V-0 in polyamide at about 15 wt% and a DOPO derivative reaches V-0 in epoxy at 0.25 to 1.2 wt% phosphorus in published studies, while mineral flame retardants need 60 wt% and more. The counter-argument is regulatory. TBBPA, the reactive bromine chemistry in the same FR-4 laminates, has been on the REACH Candidate List since 17 January 2023 and carries a harmonised Carc. 1B H350 classification from 1 September 2025 under Delegated Regulation (EU) 2024/197; boehmite carries neither. Match the chemistry to the polymer and the target rating with the flame retardant selector by polymer and UL 94 rating.
Who Manufactures Boehmite? Grades and Suppliers#
Boehmite for plastics comes from a short supplier list: Nabaltec sells it under the Apyral AOH and Actilox brands, with separate grade families for flame retardancy and for battery-separator coating. Nabaltec is the only boehmite producer recorded in our source library, and this page names no second company, because a supplier list is useful only if every entry has been verified. Individual grade designations within the two brand families are published by the manufacturer but are not recorded here, so Table T7 leaves the grade column open.
Table T7. Boehmite producers, brands and grades.
| Producer | Country / note | Brand | Grades | Use |
|---|---|---|---|---|
| Nabaltec AG | the only boehmite producer recorded in our source library | Apyral AOH | grade designations not recorded in our source library | flame-retardant boehmite for plastics |
| Nabaltec AG | as above | Actilox | grade designations not recorded in our source library | flame-retardant and specialty boehmite grades |
Grade selection turns on 4 variables that no standard fixes. Buyers should ask the supplier for the technical data sheet, the safety data sheet, the surface treatment and the median particle size, because none of these is standardised across grades, and two boehmites with the same CAS number can behave differently in the same epoxy. More producers and their certifications are in the directory of flame retardant manufacturers and suppliers.
Where Does Boehmite Come From, and Where Else Is It Used?#
Boehmite reaches plastics as an industrial mineral: it is one of the aluminium minerals that make up bauxite, and most of the material and most of the interest in it belong to aluminium production, ceramics, catalysts and lithium-ion batteries rather than to compounding. That split shows in the search results: the head term returns mineralogy databases, ceramic suppliers and battery-separator articles, and the plastics use appears only on qualified variants. Mineral supply and raw-material risk across the family are tracked on flame retardants market. The 3 non-plastics contexts below carry no dosage, no market size and no performance claim.
Boehmite as a bauxite mineral#
Boehmite is a mineral name before it is a product name: our source library records it as gamma-AlO(OH), also spelled böhmite, with a mineral specific gravity of 3.00 to 3.07 and a Mohs hardness of 3 to 3.5. Those two values are mineral data, which is why this page reports the density as a specific gravity rather than a compound density. The wider mineralogical description, covering colour, crystal system, occurrence and the history of the name, is not recorded in our source library and is not reproduced here.
Boehmite coatings for lithium-ion battery separators#
The fastest-growing market for boehmite is not a plastic at all: separator films in lithium-ion batteries are coated with it, and our source library records battery separators explicitly as a non-flame-retardant use of the same mineral. The coating question is ceramic and electrochemical rather than a compounding one, so its loading and performance criteria have no counterpart in this page's data set. A buyer looking for separator-grade material is looking at a different product family under the same CAS number.
Boehmite in ceramics, catalysts and abrasives#
Outside plastics and batteries, boehmite is sold into ceramics, catalyst carriers and abrasives, which is why a search for the word returns mineral suppliers and patents rather than compounding guidance. Those three markets sit outside the scope of this reference, and our source library holds no properties, grades or specifications for them. Naming them marks the boundary between the mineral and the plastics additive that share a name.
Is boehmite hazardous?#
Boehmite is not a Substance of Very High Concern and is not restricted under the POPs Regulation or RoHS, but our source library holds no hazard classification for it, so the supplier's safety data sheet is the authority for handling it. The general debate about flame-retardant toxicity concerns halogenated and organophosphorus substances and produces no verdict for a halogen-free aluminium mineral.