Wollastonite
Wollastonite is a naturally occurring calcium metasilicate, composed of calcium oxide and silicon dioxide. It is a white mineral having a chain silicate structure. During crushing and grinding, it forms acicular particles having an aspect ratio in the range of 1:3 up to 1:15. Because of its acicular particle shape, wollastonite has a wide range of application including building products, ceramic, paint and coating, plastic, etc.
Construction
In construction application, it is used as substitute for asbestos in fire-resistant building products. The high aspect ratio structure makes it an excellent lightweight reinforcing filler improving flexural and impact strength.
Ceramic
In ceramic application, wollastonite is used in different aspects including body, glaze, porcelain, enamels and frits, and the advantages for its application are listed as followings,
- As a source of silica and calcium oxide
- A higher fired strength due to its acicular structure
- Improved bonding and superior electrical properties due to its acicular structure
- Reduces overall melting point of frits and allows faster firing
- Allows easier and more efficient pressing operation
- Reduces drying and firing shrinkage
- Reduces moisture expansion due to low moisture absorption
- Stabilizes colours present in frits and provides a matte finish
- Improves heat shock
- Low LOI minimizes gas evolution during firing and improves overall smoothness for bodies
Filler
For filler application, wollastonite is used as functional filler in a wide range of applications such as adhesive & sealants, plants and plastics, and it offers the following benefits:
- Crack resistance
- Improves mechanical properties by reinforcement of its acicular structure
- High chemical inertness and stability
- Helps in gloss control
- Reduces shrinkage
- Helps neutralize acid shifts and prevents corrosion (pH 10)
- Medium to high resistance to abrasion (Mohs Hardness 5.0)
- Rheology control due to presence and absence of acicular shape