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    Related: Flame Retardant Additive Magnesium Hydroxide Antimony Trioxide
    • Aluminum Hydroxide CAS 21645-51-2

    Aluminum Hydroxide CAS 21645-51-2

    Aluminum Hydroxide (CAS 21645-51-2) is a functional inorganic filler serving as a halogen-free flame retardant and smoke suppressant in polymer composites and solid surface materials. Chemically identified as Alumina trihydrate or ATH, this white powder acts effectively to release chemically bound water molecules at elevated temperatures, thereby mitigating combustion in cable sheathing and engineering plastics. As a high-purity Aluminum trihydroxide, it ensures high whiteness and optimal dispersion within thermoset resin systems and construction coatings. We ensure bulk supply capabilities for this material, providing access to competitive factory pricing and customized specifications to meet specific particle size distribution needs. Full technical documentation, including MSDS, TDS, COA, is available to support compliance and safety protocols.

    • CAS: 21645-51-2
    • Synonyms: Alumina trihydrate, ATH, Hydrated alumina, Aluminum trihydroxide
    • Einecs: 244-492-7
    • Molecular Formula: Al(OH)3
    • Grade: Flame Retardant Grade (ATH), Industrial Grade, High Whiteness Filler Grade, Ultra-fine Grade
    • Package: 25kg/bag (paper-plastic composite), 500kg/1000kg Jumbo bags, or customized neutral packaging.
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    Product Description

    Aluminum Hydroxide (𝐴𝑙(𝑂𝐻)3) from Industrochem is a non-toxic, halogen-free, and environmentally friendly inorganic flame retardant. Our powder is produced through the Bayer process, followed by specialized grinding and classification to achieve specific surface areas and particle sizes.
    The primary advantage of our ATH powder lies in its thermal decomposition: at approximately 200°C, it undergoes an endothermic reaction, releasing water vapor to dilute combustible gases and forming a protective alumina layer on the material surface. This “three-in-one” function—flame retardancy, smoke suppression, and filling—makes it the most cost-effective solution for cables, rubber, and thermoset plastics. Additionally, our high-whiteness grades serve as premium fillers for artificial marble and solid surfaces, providing excellent translucency and mechanical strength.

    1 Physicochemical Properties
    2 Applications
    3 Storage Conditions
    4 Safety Precautions

    Physicochemical Properties

    PropertyStandard Grade (Typical)High Whiteness GradeUltra-Fine Grade
    Al(OH)3 Content≥ 99.6%≥ 99.8%≥ 99.9%
    Al2O3 Content≥ 65.1%≥ 65.2%≥ 65.3%
    Whiteness≥ 93%≥ 97%≥ 98%
    Moisture (H2O)≤ 0.2%≤ 0.15%≤ 0.2%
    SiO2 Content≤ 0.01%≤ 0.005%≤ 0.005%
    Fe2O3 Content≤ 0.01%≤ 0.008%≤ 0.002%
    Na2O Content≤ 0.2%≤ 0.15%≤ 0.1%
    Particle Size (D50)10 – 15 μm5 – 8 μm1 – 3 μm
    Oil Absorption22 – 26 ml/100g28 – 35 ml/100g40 – 50 ml/100g
    pH Value8.0 – 10.08.0 – 9.58.5 – 10.0

    Applications

    1. Flame Retardant Filler: The most widely used halogen-free flame retardant for PVC, PE, EVA, and epoxy resins. Ideal for wire and cable compounds, insulators, and conveyor belts.
    2. Artificial Marble & Solid Surfaces: High-whiteness ATH is the primary filler for acrylic and polyester resins, providing the “stone-like” appearance, fire resistance, and easy-to-clean properties.
    3. Glass & Ceramics: Used as a raw material to increase chemical resistance, thermal shock resistance, and mechanical strength in glass formulations and ceramic glazes.
    4. Paper Coating: Acts as a high-brightness pigment and flame-retardant coating in decorative and technical papers.
    5. Water Treatment: Serves as a raw material for the production of Polyaluminum Chloride (PAC) and Aluminum Sulfate coagulants.
    6. Catalyst Carrier: High-purity grades are used in the petrochemical industry as a substrate for various catalysts.

    Storage Conditions

    • Environment: Store in a cool, dry, and well-ventilated warehouse.
    • Moisture Control: Aluminum Hydroxide is prone to moisture absorption; ensure bags remain sealed. Do not store directly on concrete floors; use pallets.
    • Contamination Prevention: Keep away from strong acids and alkaline substances to maintain chemical purity.
    • Stacking: Limit stacking height to prevent caking of ultra-fine powders.

    Safety Precautions

    • Dust Protection: Although non-toxic, the powder is a nuisance dust. Wear an approved dust mask (N95/P2) and safety goggles during handling.
    • Skin Contact: May cause mild dryness or irritation. Wear protective gloves and wash hands after use.
    • Handling: Use local exhaust ventilation to minimize airborne dust concentrations.
    • Environmental: ATH is stable and non-hazardous to the environment, but large spills should be contained and vacuumed to prevent entering drainage systems.

    FAQ - Technical & Supply Chain

    • Q:

      What is Aluminum Hydroxide CAS 21645-51-2?

      A: Aluminum hydroxide, also called alumina trihydrate or ATH, is an inorganic white powder with the formula Al(OH)3. It is used mainly as a halogen-free flame-retardant filler, smoke suppressant and high-whiteness functional filler in polymers and solid-surface materials.
    • Q:

      How does Aluminum Hydroxide work as a halogen-free flame retardant?

      A: ATH decomposes endothermically, typically beginning around 180-200 C and peaking near 220-240 C. It releases chemically bound water, cools the polymer, dilutes combustible gases and forms a protective alumina layer, which also helps suppress smoke.
    • Q:

      Why is ATH used in solid-surface and artificial-marble products?

      A: High-whiteness ATH provides controlled translucency, fine particle size, low iron content and flame resistance. These properties improve appearance, wear and safety performance in filled acrylic, MMA or unsaturated-polyester solid-surface sheets and artificial marble.
    • Q:

      What are the main industrial applications of Aluminum Hydroxide CAS 21645-51-2?

      A: Beyond solid-surface products, ATH is used in wire and cable compounds, thermoset plastics, rubber, adhesives, coatings, electronic laminates and as an intermediate for alumina or aluminum salts.
    • Q:

      Which Aluminum Hydroxide grade should I choose for solid surface or cable compounds?

      A: Match the grade to the resin and process. Solid-surface and artificial-marble work usually needs high whiteness, low iron and controlled D50; cable and plastic formulations often prioritize a flame-retardant grade with suitable particle size, moisture and surface treatment.
    • Q:

      What specifications should I request before ordering Aluminum Hydroxide?

      A: Request Al(OH)3 content, loss on ignition, moisture, D50 or particle-size distribution, whiteness, oil absorption and trace metal content such as iron. These values affect resin demand, viscosity, color consistency, loading level and final performance.

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