How to Reduce the Abrasiveness of ATH Filler

Alumina Trihydrate (ATH) filler can cause abrasion to extruder screws, kneader blades, mixing vessels, moulds and calendaring rolls. The abrasive behaviour mainly comes from particle crystal shape, sharp fracture edges, hard impurities, oversized grit and particle hardness. Reducing ATH abrasiveness is critical for extending equipment service life, lowering maintenance cost and avoiding metal contamination in flame‑retardant polymers, sealants, rubber and coatings. This article references ATH processing technology from ath‑mill.com and JACAN powder engineering.

1. Select proper ATH raw crystal morphology

Morphology is the root factor of abrasion.

• Prefer precipitated ATH with smooth, blocky/equant hexagonal crystals. Its rounded crystal edges produce far less wear than ground natural gibbsite.
• Avoid high‑aspect‑ratio acicular or heavily fractured irregular ATH. Sharp fractured edges act like micro‑cutting tools and strongly abrade metal surfaces.
• Eliminate hard mineral impurities: quartz, corundum and iron oxide contaminants in natural ground gibbsite are much harder than ATH itself and are the main source of severe abrasion. Purify raw ore to remove siliceous hard grit.

2. Optimize milling process to remove sharp fracture edges

Traditional high‑impact crushing creates sharp broken particle edges. The milling route must be adjusted:

• Adopt low‑shear, low‑impact closed‑circuit ultrafine grinding instead of high‑velocity impact milling. Gentle grinding reduces sharp fracture surfaces and preserves native smooth crystal habit.
• Use air classification to cut coarse oversize particles. Even a small fraction of coarse oversized ATH drastically increases abrasion. Strict D97 control removes large grit.
• Prevent over‑grinding: excessive milling generates micro‑fractured sharp fines and raises specific surface area without performance gain.

3. Use ceramic‑lined milling and classification equipment (not reduce powder abrasion, but avoid metal contamination)

This step does not lower the inherent abrasiveness of ATH powder, but stops iron pickup during powder production. JACAN uses ceramic liners and ceramic turbine classifiers for ATH processing. It eliminates steel wear debris entering the powder, which is essential for electrical‑grade and light‑colour composite formulations.

4. Surface modification to buffer particle‑metal contact

Surface coating softens the particle surface boundary and reduces direct hard‑particle contact with metal equipment surfaces.

• Silane or stearic acid surface modification forms an organic lubricating layer on ATH crystal surfaces. The coating reduces friction between ATH particles and metal surfaces during mixing and extrusion.
• Fully covered particles slide rather than scrape against metal surfaces. Incomplete coating leaves exposed crystal edges, so high surface coverage rate is required.

5. Formulation adjustments in polymer compounding

• Gradually reduce coarse fractions and select a finer, narrow‑PSD ATH grade. Finer, uniform particles have lower individual cutting force than large particles.
• Add processing lubricants / wax dispersants: polyethylene wax, fatty acid ester or silicone processing aids reduce friction between ATH particles and metal surfaces during extrusion or kneading.
• Optimize filler loading: ultra‑high ATH loading increases total particle‑metal contact frequency and accelerates wear. Balance flame‑retardant performance and abrasion risk.
• Use wear‑resistant coating on production equipment: nitriding, tungsten carbide or ceramic coating on screw, barrel and kneader parts protects machinery as a complementary measure.

6. Quality control indicators for low‑abrasion ATH

Key test items to verify low‑abrasion ATH:

• Hard impurity content (quartz, corundum)
• Particle morphology inspection via SEM to check sharp fractured edges
• Oversize residue (D97)
• Metal contamination test (Fe content)
• Taber abrasion test for final composite

Common pitfalls

1. Confusing powder hardness with abrasiveness: ATH itself is relatively soft; most abrasion comes from sharp edges and hard impurity grit, not pure gibbsite crystal.
2. Relying only on surface modification: coating cannot eliminate wear caused by coarse quartz impurities. Raw material purification is mandatory.
3. Using high‑impact grinding to achieve ultrafine size: this creates sharp fractured particles and raises abrasion significantly.

To reduce ATH filler abrasiveness, the priority is to select smooth blocky precipitated ATH and remove hard mineral impurities. Then apply gentle low‑impact grinding and precision classification to eliminate coarse grit and sharp fractured edges. Uniform organic surface modification adds a lubricating boundary layer. Combined with formulation lubricants and equipment wear protection, this package minimizes abrasive wear on processing machinery while keeping flame‑retardant and mechanical properties of polymer composites.