Wollastonite ST (Solution annealed)
Heat-treated state
Choose for polymer compounds (PA, PP, PBT, phenolic) where coupling agent is needed for strength, impact and low moisture pickup.
Values for the ST condition
Other Wollastonite tempers and conditions
Wollastonite is listed in 4 conditions; see the grade overview at Wollastonite.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ACICDefault Acicular high-aspect-ratio powder | Default general-purpose grade: needle-like particles (aspect ratio ~15:1–20:1) for reinforcing ceramics, plastics, coatings and friction materials. | — | 350 | 0.1 | 380 HV | 3 W/m·K |
STThis page Solution annealed | Choose for polymer compounds (PA, PP, PBT, phenolic) where coupling agent is needed for strength, impact and low moisture pickup. | — | 350 | 0.3 | 380 HV | 2 W/m·K |
Finely milled blocky powder | Pick when low viscosity, high loading and smooth surface finish matter more than reinforcement (paints, sanitaryware bodies, glazes, adhesives). | — | — | 0.1 | 380 HV | 3 W/m·K |
Calcined / high-brightness ceramic grade | Use for wall tile, sanitaryware and low-loss electrical ceramic bodies needing minimum LOI, low iron and high whiteness for fast firing. | — | — | 0.1 | 400 HV | 3 W/m·K |
What is Wollastonite ST?
Wollastonite ST is Wollastonite heat treated to ST — choose for polymer compounds (PA, PP, PBT, phenolic) where coupling agent is needed for strength, impact and low moisture pickup. Wollastonite ST has a tensile strength of 350 MPa (50.8 ksi), stronger than 71% of ceramic grades. Elongation at break is 0.3% and the elastic modulus is 110 GPa (16 Msi). Wollastonite ST has a density of 2.85 g/cm³ (0.103 lb/in³), lighter than 79% of ceramic grades. It melts at 1,540°C (2,804 °F). ACIC is the default condition FabDigit quotes; ST is available on request or by drawing note.
Advantages
- Low embodied carbon — 0.12 kg CO₂/kg, better than 100% of ceramic grades
- Ductile — tolerates forming and impact — 0.3%, better than 91% of ceramic grades
- Easy to machine — 45/100, better than 86% of ceramic grades
- Lightweight — 2.85 g/cm³ (0.103 lb/in³), better than 79% of ceramic grades
Limitations
- Poor heat conductor — 2.4 W/m·K (1.39 BTU/hr·ft·°F), worse than 86% of ceramic grades
- Needs corrosion protection — 48/100, worse than 85% of ceramic grades
- Limited service temperature — 300°C (572 °F), worse than 82% of ceramic grades
Wollastonite ST properties
Typical room-temperature values for Wollastonite ST; 14 are specific to this condition. Other listed values are Wollastonite reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
Wollastonite ST has a density of 2.85 g/cm³ (0.103 lb/in³), lighter than 79% of ceramic grades. It melts at 1,540°C (2,804 °F).
Mechanical12
Wollastonite ST has a tensile strength of 350 MPa (50.8 ksi), stronger than 71% of ceramic grades. Elongation at break is 0.3% and the elastic modulus is 110 GPa (16 Msi).
Thermal5
Wollastonite ST is rated for continuous service to 300°C (572 °F). It conducts heat at 2.4 W/m·K (1.39 BTU/hr·ft·°F), worse than 86% of ceramic grades. Thermal expansion is 6.5 µm/m·K (3.61 µin/in·°F).
Electrical4
Wollastonite ST has an electrical resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (48/100), worse than 85% of ceramic grades.
Sustainability4
Producing a kilogram of Wollastonite ST takes about 2 MJ of energy and emits 0.12 kg of CO₂ — less than 100% of ceramic grades. Typical recycled content is 0%.
Manufacturability1
Wollastonite ST's machinability is fair (45/100, better than 86% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Wollastonite ST
Is Wollastonite easy to machine?
Fired wollastonite bodies are green-machinable before firing and require diamond tooling after firing; the powder itself is only mildly abrasive (Mohs 4.5), so it is gentle on compounding screws and paint mills compared with silica or alumina fillers.
Can Wollastonite be welded?
Not weldable; ceramic parts are joined by glass-frit sealing, glaze bonding or inorganic/epoxy adhesives.
Can Wollastonite be formed, bent or molded?
Dry-pressed, extruded or slip-cast in ceramic bodies where its low LOI and acicular habit give fast firing and very low shrinkage; as a filler it is melt-compounded at 15–40 wt % into thermoplastics or dispersed in coatings and friction resins.
What surface finishes work on Wollastonite?
Fired bodies accept conventional glazes and can be lapped/polished to a semi-gloss; in polymers the acicular grade slightly reduces surface gloss unless silane-treated fine grades are used.
Wollastonite chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiO2theoretical CaSiO3 = 51.7 % SiO2 | 48 – 52.5 | 51.7 |
| Fe2O3lower in high-brightness ceramic grades | 0.05 – 0.9 | 0.35 |
| Al2O3 | 0.1 – 1.2 | 0.45 |
| MgOfrom diopside/calcite accessories | 0.1 – 1.5 | 0.5 |
| MnO | 0 – 0.2 | 0.05 |
| TiO2 | 0 – 0.1 | 0.03 |
| K2O+Na2O | 0 – 0.5 | 0.15 |
| LOI<0.5 % for calcined grades | 0.2 – 3 | 1 |
| CaOtheoretical 48.3 % | ≥ 43 (balance) | — |
Wollastonite ST — frequently asked
What is Wollastonite ST used for?
Wollastonite ST is typically used for low-shrinkage tile bodies, ceramic glaze fluxing agent, friction material filler and reinforcing filler in composites. In short: very low firing shrinkage; acicular reinforcing filler; low-abrasion mineral filler.
What is the tensile strength of Wollastonite ST?
Wollastonite ST has a typical tensile strength of 350 MPa (50.8 ksi) — stronger than 71% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is Wollastonite ST easy to machine?
Reasonably — machinability is rated fair (45/100, better than 86% of ceramic grades). Fired wollastonite bodies are green-machinable before firing and require diamond tooling after firing; the powder itself is only mildly abrasive (Mohs 4.5), so it is gentle on compounding screws and paint mills compared with silica or alumina fillers.
Can Wollastonite ST be welded?
Not weldable; ceramic parts are joined by glass-frit sealing, glaze bonding or inorganic/epoxy adhesives.
What surface finishes work on Wollastonite ST?
Fired bodies accept conventional glazes and can be lapped/polished to a semi-gloss; in polymers the acicular grade slightly reduces surface gloss unless silane-treated fine grades are used.
Can Wollastonite ST be formed, bent or molded?
Dry-pressed, extruded or slip-cast in ceramic bodies where its low LOI and acicular habit give fast firing and very low shrinkage; as a filler it is melt-compounded at 15–40 wt % into thermoplastics or dispersed in coatings and friction resins.
What is the maximum service temperature of Wollastonite ST?
Wollastonite ST is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Industrial Minerals & Rocks — Wollastonite chapter — SME (2006)
- Handbook of Fillers, 4th ed. — ChemTec Publishing (2016)
- Wollastonite functional filler grades (acicular / surface-treated) — Imerys / NYCO Minerals (2023)
- Mineral Commodity Summaries — Wollastonite — USGS (2024)
- GB/T (wollastonite powder for ceramics and fillers) product specifications (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.