Advantages of Magnesium Hydroxide Flame Retardant

Advantages of Magnesium Hydroxide Flame Retardant

Magnesium hydroxide is a traditional type of filler-based flame retardant. When exposed to heat, it decomposes and releases bound water, absorbing a significant amount of latent heat. This reduces the surface temperature of the composite material in flames, inhibiting polymer decomposition and cooling the generated flammable gases. Magnesium hydroxide is a promising inorganic flame-retardant filler for polymer-based composites. Like aluminum hydroxide, it functions by absorbing heat through thermal decomposition and releasing water, making it non-toxic, low-smoke, and environmentally friendly, as the resulting magnesium oxide is stable and does not cause secondary pollution.

However, compared to halogen-containing organic flame retardants, achieving the same flame-retardant effect requires a filling ratio of over 50%. Since magnesium hydroxide is inorganic, its surface has poor compatibility with polymer substrates. Such a high filling ratio, without surface modification, would degrade the mechanical properties of the composite material. Therefore, surface modification is necessary to improve its compatibility with polymer substrates, ensuring that the mechanical properties of the filled material are not compromised—or even enhanced in some aspects.

Throughout the flame-retardant process, magnesium hydroxide does not produce any harmful substances. Moreover, its decomposition products can absorb large amounts of toxic gases and smoke generated by the combustion of rubber, plastics, and other polymers. Active magnesium oxide continuously adsorbs incompletely burned molten residues, quickly extinguishing flames while eliminating smoke and preventing melt dripping. It is a traditional eco-friendly inorganic flame retardant.

Currently, aluminum hydroxide is more widely used in China. However, as polymer processing temperatures increase, aluminum hydroxide tends to decompose, reducing its flame-retardant efficiency. In comparison, magnesium hydroxide offers the following advantages:

1. Higher Thermal Decomposition Temperature – Magnesium hydroxide decomposes at 340°C, which is 100°C higher than aluminum hydroxide. This allows for higher plastic processing temperatures, improving extrusion efficiency, enhancing plasticization, reducing molding time, and ensuring high surface gloss with fewer defects while maintaining strong peel strength.
2. Uniform Particle Size & Good Compatibility – Its even particle distribution ensures better compatibility with substrates, minimizing the impact on the mechanical properties of the product.
3. Formation of a Protective Barrier – After dehydration during combustion, the resulting magnesium oxide is a high-strength, heat-resistant material that acts as a protective barrier, isolating flames and toxic gases. Magnesium hydroxide also neutralizes acidic gases (SO₂, NOx, CO₂) produced during plastic combustion.
4. High Decomposition Efficiency & Smoke Suppression – It exhibits strong flame-retardant and smoke-suppressing capabilities while being less abrasive to equipment, thereby extending machine lifespan.
5. Cost-Effective – Magnesium hydroxide flame retardant is half the price of aluminum hydroxide. Its high filling capacity significantly reduces production costs.

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