What is Antimony Trioxide CAS 1309-64-4?

Antimony Trioxide, also called diantimony trioxide or antimony(III) oxide, CAS 1309-64-4, is the inorganic compound Sb2O3. It is a white crystalline powder with high thermal stability, very low water solubility, and a density of about 5.2-5.7 g/cm3.

Why is Antimony Trioxide called a flame-retardant synergist?

Antimony Trioxide generally does not provide sufficient flame retardancy by itself. It is called a synergist because it works with halogenated flame retardants, where the antimony and halogen form flame-inhibiting antimony halide species during combustion and improve self-extinguishing performance.

How is Antimony Trioxide used with halogenated flame retardants?

It is normally combined with brominated or chlorinated flame retardants in PVC, cable compounds, rubber, plastics, textiles and coatings. The ratio and grade depend on the polymer and the halogen source, and the combination is more effective than either component alone.

What are the main applications of Antimony Trioxide?

The main use is as a flame-retardant synergist in PVC, cables, rubber, plastics, textiles and coatings. It is also used in glass and ceramics, and in pigment-related applications where controlled whiteness and dispersion are important.

What grades and forms are available for industrial handling?

Industrial grades commonly specify Sb2O3 content around 99.5% or higher, with particle size and residue limits selected for the end use. Besides standard powder, dust-free wetted grades using DOP, DIDP, DINP or similar wetting agents and pre-dispersed masterbatch forms are available to reduce dust and improve dispersion.

Antimony Trioxide CAS 1309-64-4

Antimony Trioxide (CAS 1309-64-4), commercially abbreviated as ATO, is a critical inorganic compound utilizing its synergistic reaction mechanism to significantly enhance the efficacy of halogenated flame retardants. Chemically identified as Antimony(III) oxide, this high-whiteness, fine crystalline powder functions not as a standalone retardant, but as a powerful synergist that reacts with chlorine or bromine sources to form volatile antimony halides, which scavenge free radicals and inhibit combustion. As the industry-standard Flame Retardant Synergist, it is extensively integrated into plastics (PVC, ABS, HIPS), rubber, textiles, and coatings to achieve high fire safety ratings (such as UL94 V-0). Additionally, high-purity grades serve as an essential polymerization catalyst in the manufacturing of PET (Polyethylene Terephthalate) resins and fibers. We ensure bulk supply capabilities for this material, providing access to competitive factory pricing and customized specifications to meet specific particle sizes (e.g., 0.5μm, 1.0μm) and whiteness standards. Full technical documentation, including MSDS, TDS, COA, is available to support compliance and safety protocols. For formulations requiring an inorganic smoke-suppressant or char-promoting additive, Zinc Borate is a related material to compare by polymer system, particle size and flame-retardant package.

CAS: 1309-64-4
Synonyms: Antimony(III) oxide, Diantimony trioxide, ATO, Antimonous oxide, Antimony oxide, Sb2O3
Einecs: 215-175-0
Molecular Formula: Sb₂O₃
Grade: Industrial Grade
Package: 25 kg bag (standard); 500 kg / 1000 kg big bag optional

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Product Description

ATO is a white crystalline powder with high thermal stability and very low water solubility. In flame-retardant systems, it acts as a synergist that can promote formation of flame-inhibiting species during combustion and improve self-extinguishing performance (formulation-dependent). It is also used where consistent whiteness, dispersibility and stable performance are required in processing.

1 Physicochemical Properties

2 Applications

3 Storage Conditions

4 Safety Precautions

Physicochemical Properties

Typical values; final specs follow COA by batch and grade.

Item	Typical Value / Specification
Appearance	White powder / white crystalline powder
CAS	1309-64-4
EC (EINECS)	215-175-0
Molecular formula	Sb₂O₃
Molecular weight	291.52 g/mol
Density	~5.2–5.7 g/cm³ (polymorph dependent)
Melting point	~656 °C
Boiling / behavior	Sublimes at high temperature (commonly reported)
Solubility in water	Insoluble / very low solubility
Solubility in acids	Soluble in acids (formulation/acid strength dependent)

Applications

Flame-retardant synergist in PVC/cables, rubber, plastics and certain textiles/coatings (used with compatible FR packages)
Masterbatch / polymer compounding as a functional additive where stable whiteness and dispersion are required
Glass/ceramics & pigment-related uses (process-dependent; user trial recommended)

For other flame-retardant additives that may be reviewed alongside antimony trioxide, see Zinc Borate and Melamine Cyanurate.

Storage Conditions

Store in a cool, dry, well-ventilated warehouse, in tightly sealed original packaging.
Keep away from moisture and dust contamination; avoid unnecessary dust generation during handling.
Keep away from strong oxidizers and incompatible reactive chemicals.
Shelf life: typically 24 months under proper storage (depends on packaging and humidity control).

Safety Precautions

Avoid inhalation of dust; use local exhaust ventilation and dust mask/respirator when handling powders.
Wear protective gloves and safety goggles; wash hands after handling.
Many SDS/CLP classifications list Antimony(III) oxide as Carcinogenicity Category 2 (H351: suspected of causing cancer); follow SDS and local regulations for workplace exposure control.
Spills: avoid raising dust; collect using suitable methods and dispose according to local rules.

FAQ - Technical & Supply Chain

Q:
What is Antimony Trioxide CAS 1309-64-4?

A: Antimony Trioxide, also called diantimony trioxide or antimony(III) oxide, CAS 1309-64-4, is the inorganic compound Sb2O3. It is a white crystalline powder with high thermal stability, very low water solubility, and a density of about 5.2-5.7 g/cm3.
Q:
Why is Antimony Trioxide called a flame-retardant synergist?

A: Antimony Trioxide generally does not provide sufficient flame retardancy by itself. It is called a synergist because it works with halogenated flame retardants, where the antimony and halogen form flame-inhibiting antimony halide species during combustion and improve self-extinguishing performance.
Q:
How is Antimony Trioxide used with halogenated flame retardants?

A: It is normally combined with brominated or chlorinated flame retardants in PVC, cable compounds, rubber, plastics, textiles and coatings. The ratio and grade depend on the polymer and the halogen source, and the combination is more effective than either component alone.
Q:
What are the main applications of Antimony Trioxide?

A: The main use is as a flame-retardant synergist in PVC, cables, rubber, plastics, textiles and coatings. It is also used in glass and ceramics, and in pigment-related applications where controlled whiteness and dispersion are important.
Q:
What grades and forms are available for industrial handling?

A: Industrial grades commonly specify Sb2O3 content around 99.5% or higher, with particle size and residue limits selected for the end use. Besides standard powder, dust-free wetted grades using DOP, DIDP, DINP or similar wetting agents and pre-dispersed masterbatch forms are available to reduce dust and improve dispersion.

Ordering & Documentation

Key information for document requests, quotations, and supply planning.

Documents

COA, TDS, SDS/MSDS and packing details are available on request.

Quotation

Send the CAS number, grade, quantity, packing preference and destination.

Sample & Supply

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Storage & Shipping

Product-specific conditions are confirmed before order.

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