Aluminum Hydroxide (ATH), chemically known as Al(OH)₃ and commonly identified by CAS No. 21645-51-2, is one of the most widely used non-halogenated flame retardant fillers in Low Smoke Halogen-Free (LSZH) materials. With the growing global demand for safer, environmentally friendly cable compounds and polymer systems, ATH has become an essential component in modern fire-safe formulations.

What is Low Smoke Halogen-Free (LSZH)?

Low Smoke Halogen-Free materials are designed to minimize the release of toxic gases, corrosive fumes, and dense smoke during combustion. Traditional halogen-containing flame retardants may emit hazardous substances such as hydrogen chloride (HCl) when exposed to fire, posing significant risks to both human health and electronic equipment. In contrast, LSZH compounds formulated with aluminum hydroxide provide an environmentally responsible alternative that meets increasingly stringent international fire safety standards.

Flame Retardant Mechanism of Aluminum Hydroxide

Aluminum hydroxide functions as a highly effective inorganic flame retardant through an endothermic decomposition process. When exposed to temperatures above approximately 200°C, ATH decomposes into aluminum oxide (Al₂O₃) and releases chemically bound water vapor. This reaction delivers three major fire-protection benefits:

1. Heat absorption: The endothermic reaction absorbs a large amount of heat, slowing down temperature rise.

2. Dilution effect: The released water vapor dilutes combustible gases and oxygen around the flame zone.

3. Protective barrier formation: The residual aluminum oxide forms a stable, insulating layer on the polymer surface, reducing heat transfer and preventing further combustion.

Because this mechanism is purely physical rather than chemical halogen-based inhibition, ATH does not generate toxic or corrosive gases during burning.

Applications in Cable and Wire Compounds

Aluminum hydroxide is extensively used in LSZH cable compounds for power cables, communication cables, building wires, and fiber optic systems. It is particularly suitable for polyethylene (PE), ethylene-vinyl acetate (EVA), and other thermoplastic elastomers.

In these applications, ATH offers:

• Excellent flame retardancy

• Low smoke density

• Non-toxic and non-corrosive combustion products

• High electrical insulation performance

• Good arc resistance

The use of high-purity, fine-particle ATH ensures excellent dispersion within polymer matrices, maintaining mechanical properties such as tensile strength and elongation while achieving required flame-retardant ratings (such as IEC and UL standards).

Environmental and Regulatory Advantages

As global regulations increasingly restrict halogenated flame retardants, aluminum hydroxide provides a sustainable and compliant solution. It is non-toxic, environmentally friendly, and compliant with major international directives such as RoHS and REACH. Its natural abundance and stable supply chain further make it a cost-effective choice for large-scale cable manufacturing.

Performance Optimization

To meet specific technical requirements, manufacturers often select surface-treated or ultra-fine grades of aluminum hydroxide to enhance compatibility with polymers and improve mechanical performance. Advanced processing technologies allow higher filler loading while maintaining flexibility and processability.

Conclusion

Aluminum hydroxide remains one of the most reliable and economical flame retardant solutions for Low Smoke Halogen-Free applications. Its unique combination of fire resistance, smoke suppression, environmental safety, and electrical performance makes it indispensable in modern cable and polymer industries. As safety standards continue to rise worldwide, ATH will play an increasingly important role in delivering safer and more sustainable flame-retardant materials.