What is Гидроксид алюминия (ATH)?
Aluminum hydroxide, chemical formula Al(OH)₃, is a white inorganic powder and the most widely used non-toxic flame retardant in the world. When heated above 200°C, it decomposes endothermically into aluminum oxide (Al₂O₃) and water vapor:
2 Al(OH)₃ → Al₂O₃ + 3 H₂O (ΔH ≈ +1,000 kJ/kg)
This decomposition absorbs heat (cooling the polymer), releases water vapor (diluting flammable gases), and leaves a protective ceramic char. The combination of these three mechanisms gives ATH its excellent flame-retardant performance without the toxic smoke produced by halogenated flame retardants.
ATH is FDA-approved for food contact, REACH-compliant in Europe, and classified as non-hazardous under GHS. It is the preferred flame retardant for LSZH (Low Smoke Zero Halogen) cables, E&E applications, building products, and any application where toxic smoke is a safety concern.
Technical Specifications
Standard ATH Grades — Three Purity Levels
| Parameter | Standard | High Purity | Ultra White |
|---|---|---|---|
| Al(OH)₃ (%) | ≥99.5 | ≥99.7 | ≥99.8 |
| SiO₂ (%) | ≤0.02 | ≤0.01 | ≤0.005 |
| Fe₂O₃ (%) | ≤0.02 | ≤0.01 | ≤0.005 |
| Na₂O (%) | ≤0.30 | ≤0.20 | ≤0.10 |
| CaO (%) | ≤0.03 | ≤0.02 | ≤0.01 |
| Whiteness (R457) | ≥93 | ≥96 | ≥98 |
| Moisture (%) | ≤0.3 | ≤0.2 | ≤0.2 |
| Specific Gravity (g/cm³) | 2.40 | 2.40 | 2.40 |
| Mohs Hardness | 2.5-3.0 | 2.5-3.0 | 2.5-3.0 |
| Decomposition Temp (°C) | 200-220 | 200-220 | 200-220 |
| Water Loss at 200°C (%) | ≤0.3 | ≤0.2 | ≤0.2 |
Standard Particle Size Grades
| Grade | D50 (μm) | Top Cut (μm) | Primary Application |
|---|---|---|---|
| ATH-1 | 1.0-1.5 | ≤10 | Premium LSZH cable, high-gloss FRP |
| ATH-2 | 2.0-3.0 | ≤15 | Standard cable compounds, artificial marble |
| ATH-5 | 5.0-7.0 | ≤25 | Rubber products, conveyor belts |
| ATH-10 | 10-15 | ≤45 | General purpose thermoset plastics |
| ATH-25 | 20-25 | ≤75 | Cost-sensitive applications, fillers |
Surface Treatment Options
| Treatment | Best For | Loading Reduction |
|---|---|---|
| Uncoated | Thermosets (UP, EP), water-based | — |
| Vinyl Silane | PE, XLPE, EVA cable compounds | 20-30% |
| Amino Silane | Epoxy, polyurethane, phenolic | 20-30% |
| Stearic Acid | PP, PE, general purpose (low cost) | 10-15% |
| Titanate | High-temperature polymers | 25-35% |
Six Major Industrial Применение
1. LSZH Cable Compounds — Largest Application
ATH is the dominant flame retardant in LSZH (Low Smoke Zero Halogen) cable compounds for building wire, power cable, and data cable insulation. Typical loading is 150-180 phr (parts per hundred resin) in EVA-based compounds, achieving UL94 V-0 rating with oxygen index >32%. The market for ATH in cables exceeds 500,000 MT/year globally.
2. Rubber Продукция
ATH is used in flame-retardant rubber compounds for conveyor belts, cable jackets, gaskets, and seals. Loading 100-150 phr in EPDM or natural rubber provides UL94 V-0 with low smoke emission. Surface-treated ATH improves processability and dispersion.
3. Unsaturated Polyester (FRP & Artificial Marble)
ATH is the primary flame retardant in glass-fiber reinforced polyester (FRP) used in building panels, bath fixtures, and transportation. In artificial marble (cultured marble), ATH loading of 40-60% provides Class A fire rating while maintaining translucency and workability.
4. Epoxy Encapsulants & PCB Laminates
ATH-filled epoxy is used as potting compound for transformers, capacitors, and electronic modules. PCB laminates use ATH + epoxy for flame-retardant FR-4 substrates (UL94 V-0). Particle size 1-5μm is critical for thin laminates without bleed-through.
5. Latex & Carpet Назадing
ATH in latex foam backing for carpets provides flame retardancy without the toxic smoke of antimony-bromine systems. Used in commercial carpet backing and contract furniture foams.
6. Paper & Board Coatings
ATH is used as flame-retardant filler in specialty paper and paperboard for building products, packaging, and electrical insulation paper.
ATH vs MDH — Selection Guide
| Property | ATH | MDH |
|---|---|---|
| Chemical Formula | Al(OH)₃ | Mg(OH)₂ |
| Decomposition Temp | 200°C | 330°C |
| Water Loss (%) | 34.6 | 31.0 |
| Heat Absorption (kJ/kg) | ~1,000 | ~1,300 |
| Char Yield | Lower | Higher |
| Cost (relative) | Lower | Higher |
| Best For Processing <200°C | ✓ | ✓ |
| Best For Processing >250°C | ✗ (decomposes during processing) | ✓ |
| Whiteness | Excellent | Lower (grayish) |
| Common Применение | PE, EVA, XLPE, UP, epoxy | PP, PA, PBT, high-temp engineering plastics |
Frequently Asked Questions
Q: What is the difference between ATH and MDH?
A: ATH (Aluminum Hydroxide, Al(OH)₃) decomposes at 200°C releasing water vapor. MDH (Magnesium Hydroxide, Mg(OH)₂) decomposes at 330°C. Use ATH for processing temperatures below 200°C (most polymers, TPE, XLPE cables). Use MDH for higher processing temperatures (PP, PA, PBT) above 250°C. ATH is more cost-effective; MDH provides higher char yield.
Q: How much ATH do I need for UL94 V-0 rating?
A: Typical loading levels for UL94 V-0 (3.2mm thickness): EVA-based cable compounds 150-180 phr, polyethylene 60-70 wt%, polypropylene 60-65 wt%, unsaturated polyester 50-60 wt%, epoxy 50-60 wt%. Particle size 1-5μm D50 is recommended for best balance of processability and fire performance.
Q: Is ATH surface-treated necessary for polymer compatibility?
A: Yes, surface treatment significantly improves ATH dispersion in polymers and reduces melt viscosity during processing. Common treatments: vinyl silanes (best for polyethylene and XLPE), amino silanes (epoxy and polyurethane), stearic acid (general purpose, low-cost). Uncoated ATH is suitable only for thermosets and water-based applications.
Q: What is the ATH decomposition mechanism?
A: When heated above 200°C, ATH decomposes endothermically: 2Al(OH)₃ → Al₂O₃ + 3H₂O. The reaction absorbs ~1,000 kJ/kg of heat, cooling the polymer and slowing thermal decomposition. The released water vapor dilutes combustible gases and oxygen in the flame zone. The residual alumina forms a protective ceramic char layer. This combination of endothermic cooling, gas dilution, and char formation provides excellent flame retardancy.
Q: Is ATH approved for food contact applications?
A: Yes, ATH is FDA-approved under 21 CFR 184.1240 for use as a direct food additive and in food contact materials. It's widely used in food packaging films, paper coatings, and HDPE bottles. European compliance: approved under EU Regulation 10/2011 for plastic food contact. ATH is also Kosher and Halal certified.
Packaging & Delivery
- Standard: 25 kg multi-wall paper bags with PE inner liner (moisture-proof)
- Bulk: 500 kg / 1000 kg jumbo bags for full-container orders
- Super sacks: Available for orders ≥20 MT
- Container loading: 22-25 MT per 20'FCL with pallets, 25 MT per 40'FCL bulk
- Lead time: 10-15 days for stock grades, 20-30 days for custom particle size or surface treatment
- Documents: COA (with PSD), MSDS, ISO 9001, REACH compliance, FDA compliance letter, commercial invoice, B/L
- Shipping terms: FOB Qingdao / CIF / CFR / DDP available
How to Order
Tell us your application (LSZH cable / rubber / FRP / artificial marble / other), required Al(OH)₃ purity (99.5 / 99.7 / 99.8%), particle size (D50), surface treatment (uncoated / silane / stearic), monthly quantity, and delivery destination. Our engineers will recommend the right grade and provide a competitive quotation within 2 hours. Free 1-2 kg samples available for fire performance testing.