A number of important applications require alumina as filler:
- Sanitaryware : where ATH enhances the mechanical strength and improves durability. Compounds can be loaded with up to 60 % ATH (SH150).
- Brake linings: ground alumina (AC44B6 and P122B) is one component of friction materials, where alumina hardness is used to improve wear resistance.
- High-voltage insulators: for resin based insulators the very low conductivity of alumina (AC34B6) makes it an ideal filler for epoxy resin.
- Toothpaste: alumina and ATH can be used as polishing agents for teeth (SH80 and AC34B6).
- Nuclear waste transportation: thermoset resin filled with ATH (SH150) is one of the layers of protection for nuclear waste transportation. The ATH is mainly used for its ability to absorb neutrons.
- Welding fluxes: Electrodes containing alumina (AC45) are used to shield the weld area from atmospheric oxygen and nitrogen.
Fine alumina hydrate
Aluminium trihydroxide (ATH) produced by the Gardanne Bayer process is subject to controlled grinding to obtain a range of particle size distributions and low viscosity grades.
Ground calcined alumina
These aluminas are ground in continuous ball-mills or air-jet mills to median particle sizes (d50) 3, 4, 5 or 6 µm.
Hard calcined alumina
These aluminas have low specific surface area (BET < 1m²/g) and are almost entirely alpha alumina. Standard soda content is 3000-4000 ppm and intermediate soda content is 2000-3000 ppm. Hard calcined aluminas are produced in rotary kilns.
Low soda alumina
This alumina has very low soda content: between 300 and 500ppm. Carefully controlling calcination using the proprietary Reynolds process also allows a wide range of primary crystal size to be offered.