Wollastonite
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Introduction
Wollastonite (calcium silicate, chemical formula CaSiO3) exists in an acicular and non-acicular form.
Wollastonite can be characterised by:
- Shape (non-acicular/ acicular)
- Medium Mohs hardness of 5
- Alkaline nature.
Basic properties
| Property | Value | Unit |
| Shape | fibrous or blocky | – |
| Moisture | < 0.2 | [%] |
| pH | 10 | [-] |
| Hardness (Mohs) | 5 | [-] |
| Refractive index | 1.63 | [-] |
| L.O.I. | 3.5 | [%] |
| Density | 2.9 | [kg/ dm3] |
Casiflux is the product name for Sibelco’s wollastonite products.
- Acicular grades are named Casiflux F or Casiflux FG
- Blocky grades are named Casiflux G
| Product | Grade | D50
[µm] |
OA
[g/ 100 g] |
| Casiflux | FG20 | 18 | 54 |
| F75 | 28 | 59 | |
| G20 | 10.5 | 30 | |
| G38 | 18 | 28 |
Benefits:
Acicular
Reinforcement due to acicular shape e.g. improving impact resistance and flexural strength of PP-resins.
Rheology control in e.g. sealants and adhesives: due to its acicular shape, wollastonite has an impact on the rheology profile. When applying shear, the acicular particles will align and provide a low viscosity. When shear is removed, the acicular particles lose their orientation and cause the viscosity to increase above the level expected when the particles had a non-acicular shape.
Crack resistance: acicular wollastonite will reduce mud cracking in thick applied coatings.
Blocky
Abrasion resistance: due to its hardness of 5 on Mohs scale, wollastonite will increase wear resistance in the application i.e., powder coatings.
