ATH and MDH

Optimized Translation of "Aluminum Hydroxide and Magnesium Hydroxide as Inorganic Flame Retardants"

Aluminum Hydroxide (ATH) and Magnesium Hydroxide (MDH) as Halogen-Free Flame Retardants

Aluminum hydroxide (Al(OH)₃, ATH) and magnesium hydroxide (Mg(OH)₂, MDH) are widely recognized inorganic flame retardants, valued for their eco-friendliness, cost efficiency, and multifunctional flame-retardant mechanisms. This revised translation enhances clarity, technical precision, and alignment with international standards (e.g., ASTM, UL, IEC).

1.  Flame-Rardant Mechanisms

l ATH: Decomposes at 200–300°C (ΔH ≈ 1,970 J/g):

2Al(OH)₃→Al₂O₃+3H₂O↑

l MDH: Decomposes at 340–490°C (ΔH ≈ 1,370 J/g):

2Mg(OH)₂→2MgO+2H₂O↑

Both reactions absorb heat, reduce material surface temperatures, and release water vapor to dilute oxygen and suppress free radical chain reactions. Burning can form a protective char layer and suppress smoke. (Al₂O₃) form ceramic-like layers to block heat/oxygen transfer.  MgO enhances char formation in polymers, reducing smoke and toxic gas emissions.

2. Application Highlights

Environmental Compliance

Zero halogens/heavy metals; decomposition products (H₂O, Al₂O₃, MgO) comply with EU RoHS/REACH.

Key Industrial Uses

Glass Fiber-Reinforced Plastics (GFRP):

ATH (25–30 phr) + Gsflame MA-77-867/863 (3–5 phr) in epoxy/polyester resins achieves LOI >28%.

Wire & Cable:

ATH/MDH blends (100 phr) + red phosphorus (1.5–2 phr) in PE/PVC meet IEC 60332 flame spread requirements.

Rubber Foams:

ATH + Gsflame Pow RE32 in EPDM/NBR attains UL-94 V-0.

High-Frequency PCBs:

40% MDH in epoxy substrates achieves LOI 35% (UL-94 V-0), critical for 5G base stations to mitigate arc risks.

Synergy with Phosphorus-Based Combining ATH/MDH with Gsflame MA-77-867/863 or RE32 cuts total flame retardant dosage by 20–40% while enhancing flame resistance.

3. Technical Challenges & Mitigation Strategies

lATH decomposes below processing temps of engineering plastics (e.g., PC >300°C). Blend ATH with high-thermal-stability MDH; apply silane/titanate coatings to delay decomposition.

lHigh dosage (>50 wt%) can reduce physical properties of substrate. Nano-ATH/MDH (<100 nm) can solve this issue without lower addition.

lATH and MDH can absorb moisture and can cause the difficulty of dispersion. Surface hydrophobic modification or coated with stearic acid can solve the issue of absorbing moisture.

4.Future Development Directions

lNanotechnology: Nano - sized aluminum hydroxide and nano - sized magnesium hydroxide (specific surface area > 50 m²/g) can improve the flame - retardant efficiency by over 30% and enhance the transparency of materials, making them suitable for the encapsulation of electronic devices.

lComposite Synergistic Systems: Develop a new type of flame - retardant system of "aluminum hydroxide/magnesium hydroxide + two - dimensional materials (MXene, BNNS)". Improve the limiting oxygen index (LOI > 35%) through the dual mechanisms of physical barrier and catalytic char formation. Alternatively, use aluminum hydroxide/magnesium hydroxide in combination with montmorillonite, zinc borate, etc., to reduce the usage amount and improve the flame - retardant effect.