Why Is Low-Temperature Grinding Important for ATH (Aluminum Hydroxide)

Aluminum hydroxide (ATH, Al(OH)₃) is a functional halogen-free flame retardant whose commercial value depends on intact crystalline structure and complete crystal water. ATH begins irreversible dehydration when the material temperature rises above 130°C. Therefore, low-temperature grinding is not an optional optimization but a mandatory process requirement for qualified ATH production. This article explains the core risks caused by high-temperature grinding and the vital significance of stable low-temperature operation.

1. Avoid Thermal Dehydration & Preserve Flame Retardant Performance (The Most Critical Reason)

The core commercial function of ATH is endothermic flame retardancy. When exposed to fire, ATH releases crystal water to absorb heat, dilute flammable gas and suppress smoke.
Thermal reaction threshold:
>130°C: 2Al(OH)₃ → AlO(OH) + H₂O↑
Partial crystal water escapes, forming boehmite.

• Once dehydration occurs during grinding, the crystal water content permanently decreases.
• The endothermic capacity drops sharply; finished powder loses standard flame retardant efficiency for cables, plastics and coatings.
  Low-temperature grinding (stable material temperature ≤110°C) maintains the complete Al(OH)₃ crystal lattice and guarantees theoretical flame retardant performance.

2. Maintain High Whiteness & Stabilize Powder Appearance

High-temperature local hot spots inside the grinding system directly damage ATH color:

• Partial dehydration generates micro boehmite impurities, causing powder to turn yellow or gray.
• Uneven thermal reaction leads to inconsistent whiteness between production batches.
  Even high-quality raw ATH with excellent initial whiteness will be downgraded after high-temperature grinding. Strict low-temperature control avoids discoloration and keeps stable whiteness indicators required by artificial stone, high-grade plastic and coating manufacturers.

3. Prevent Rising Oil Absorption Value

Oil absorption is a key indicator for inorganic fillers.
When ATH suffers thermal dehydration:

1. Surface crystal structure changes; specific surface area abnormally increases.
2. Powder absorbs more plasticizer, resin and processing oil.
   Consequences for downstream manufacturers:

• Higher raw material costs for compounding.
• Higher melt viscosity, difficult extrusion and injection molding.
• Product surface defects, bubbles and poor surface smoothness.
  Low-temperature grinding protects the original particle surface morphology and controls oil absorption within the standard range.

4. Avoid Particle Hard Agglomeration

High temperature combined with trace free moisture triggers surface adhesion between ultrafine ATH particles:

• Fine particles bond together to form hard agglomerates that cannot be broken by simple mixing.
• Agglomerated ATH disperses poorly in polymer matrix, resulting in surface spots, reduced mechanical strength of finished plastic products.
  Controlled low-temperature environment reduces surface activity of particles and minimizes permanent agglomeration.

5. Guarantee Electrical Insulation Performance for Electronic-Grade ATH

Low-smoke halogen-free cables, electronic packaging materials require ATH with stable insulation properties.
High-temperature dehydration changes surface chemical activity of ATH particles:

• Increase soluble ion precipitation on particle surfaces.
• Lower volume resistivity of composite materials.
  Low-temperature grinding retains the inert surface characteristics of original ATH, meeting strict electrical performance standards for wire & cable and electronic components.

6. Protect Surface Modification Effect (For Activated ATH)

Most commercial ATH undergoes surface treatment with stearic acid or silane coupling agents to improve compatibility with resins.
If grinding temperature is too high:

1. Coupling agents are oxidized or decomposed and lose activity.
2. Organic modifiers volatilize rapidly.
   Low-temperature working environment ensures uniform coating of modifiers on ATH surfaces, maximizing modification efficiency.

7. Extend Service Life of Grinding System Equipment

Continuous high temperature brings extra burden to the whole production line:

• Accelerate aging of rubber sealing parts, dust filter bags and pipeline coatings.
• Increase thermal stress on mill housing, classifier rotors, causing deformation and accelerated wear.
  Stable low-temperature operation reduces equipment maintenance frequency and lowers long-term production costs.

Comparison: Quality Difference — Low-Temperature Grinding VS High-Temperature Grinding

Key Low-Temperature Implementation Measures (Brief Summary)

As recommended on ath-mill.com mature ATH process solutions:

1. Adopt water-jacketed cooling ultrafine ring roller mill or cooled ACM mill for dry grinding.
2. Match reasonable cold air circulation ventilation to remove waste heat.
3. Maintain uniform feeding, avoid no-load operation and overload operation.
4. Pre-dry raw ATH below 110°C to prevent internal material crust and hot spots.
5. Install real-time temperature monitoring and automatic alarm interlock.

Low-temperature grinding is the foundation to retain the intrinsic physical and chemical properties of aluminum hydroxide. High-temperature processing causes irreversible crystal dehydration, which damages flame retardancy, whiteness, dispersion and electrical performance simultaneously.

For dry closed-circuit ultrafine grinding lines for ATH flame retardant powder, water-cooled ring roller mill systems are the preferred solution to maintain stable low-temperature working conditions, achieve consistent finished powder quality and maximize commercial value of ATH products.