CI 77002- ▸ Flame retardant: Halogen-free flame retardant for plastics, rubber, and latex foam.
- ▸ Smoke suppressant: Smoke suppressant in polymer compounds.
- ▸ Filler: Functional filler in paper, plastics, and rubber.
- ▸ Abrasive: Soft abrasive for brass and plastics.
- ▸ Desiccant: Desiccant powder.
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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Aluminum hydroxide (ATH, alumina trihydrate) is the most-used flame retardant in the world by volume — a halogen-free mineral that decomposes endothermically, releasing water to cool and quench combustion while suppressing smoke. Identity: CAS 21645-51-2.
What it is
Aluminum hydroxide (CAS 21645-51-2, Al(OH)3) is a white mineral powder, also called alumina trihydrate or ATH. It is inexpensive, halogen-free and doubles as a functional filler and smoke suppressant, which is why it is the highest-volume flame retardant globally.
How it performs in fire
On heating above roughly 180–200°C it decomposes endothermically, absorbing heat and releasing water vapor that cools the polymer and dilutes the combustible gases; the residual alumina forms a protective surface layer and suppresses smoke. Because the effect is dilution/cooling, it is used at high loadings (often 40–65%), which affects mechanical and rheological properties. Its ~200°C decomposition point sets the upper processing temperature; for hotter polymers use magnesium hydroxide.
Applications
ATH is used in wire and cable (halogen-free flame-retardant compounds), EVA and polyolefins, rubber, unsaturated polyester and epoxy thermosets, SMC/BMC, solid-surface countertops and carpet backing. For higher processing temperatures compare magnesium hydroxide; for intumescent systems see APP.
Forms, grades and handling
ATH is supplied as a white powder in a range of particle sizes (ground and precipitated grades) in bags and bulk. Properties are typical reference values; the Certificate of Analysis (CoA) for the lot you buy governs. Handle per the current Safety Data Sheet (SDS), and confirm regulatory status and restrictions for your market and end use. Each lot ships with CoA, TDS and SDS.
Bulk supply and RFQ
RawSource sources Aluminum Hydroxide direct from producers in bulk, with CoA, TDS and SDS per lot. Tell us your polymer or system, the fire test you must pass, your maximum loading, and any particle-size or grade requirement, and we will quote the right grade. See the full range and selection logic in the flame retardants guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical / class | Flame retardant / smoke suppressant (mineral hydroxide) |
| Flame-retardant type | Mineral hydroxide (endothermic) |
| Role in fire performance | Endothermic; releases water; smoke suppressant |
| CAS Number | 21645-51-2 |
| Molecular Formula | Al(OH)3 |
| Molecular Weight | 78.0 g/mol |
| Handling | Refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 244-492-7
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Solutions Using This Product
Process-solution guides on this site that specify this chemistry:
- Halogen-Free (Non-Halogen) Flame Retardants (Plastics & Polymers)
- Flame Retardants for Textiles: APP, Mineral & N-P Systems (Textiles)
- Intumescent & Fireproofing Coating Additives (Coatings & Construction)
Frequently Asked Questions
What is aluminum hydroxide (ATH) used for?
Aluminum hydroxide (ATH/alumina trihydrate, CAS 21645-51-2) is the highest-volume flame retardant worldwide, a halogen-free mineral used in wire and cable, EVA/polyolefins, rubber, thermosets and solid surface. It decomposes endothermically, releasing water to cool and quench combustion, and suppresses smoke.
Why is ATH used at such high loadings?
ATH works by endothermic cooling and fuel dilution rather than chemical interruption, so it needs high loadings (often 40–65%) to be effective, which is why particle size and surface treatment matter for mechanical properties.
What is the difference between ATH and magnesium hydroxide?
Both are endothermic mineral hydroxides; ATH decomposes around 180–200°C and MDH around 300–340°C, so MDH is used for polymers processed at higher temperatures where ATH would decompose during compounding.
How is bulk aluminum hydroxide supplied and quoted?
RawSource supplies aluminum hydroxide in bulk with CoA, TDS and SDS per lot. Pricing is quote-based on grade, particle size and volume; submit an RFQ with your polymer/system and the fire test you must pass.
What is the REACH and TSCA regulatory status of Aluminum Hydroxide (ATH, Alumina Trihydrate)?
Aluminum Hydroxide (ATH, Alumina Trihydrate) (CAS 21645-51-2) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 244-492-7).