A hydrated Magnesium Aluminium Silicate, it is lightweight, inorganic (incombustible), compressible, highly absorbent and non-reactive and is used in thousands of applications including potting soils and grow mixes. Vermiculite is used in thousands of applications from potting soils, light weight concrete, fire protection construction materials, intumescent applications, as a UN approved packaging material for the safe shipment of hazardous liquids, texturizers in paints and coatings, and most recently as nanocomposites for films, coatings and barrier applications.
When subjected to heat vermiculite has the unusual property of exfoliating or expanding into worm-like pieces (the name vermiculite is derived from the Latin ‘vermiculare’ – to breed worms). This characteristic of exfoliation, the basis for commercial use of the mineral, is the result of the mechanical separation of the layers by the rapid conversion of contained water to steam. The increase in bulk volume of commercial grades is 8 to 12 times, but individual flakes may exfoliate as many as 30 times. There is a color change during expansion that is dependent upon the composition of the vermiculite and furnace temperature. The bulk density of crude vermiculite or vermiculite concentrate is in the range of 640-1120 kg/m³ and exfoliated or expanded vermiculite is in the range of 64-160 kg/m³
| ELEMENTS | PERCENT BY WEIGHT |
|---|---|
| SiO₂ (Amorphous) | 38–46 |
| Al₂O₃ | 10–16 |
| MgO | 16–35 |
| CaO | 1–5 |
| K₂O | 1–6 |
| Fe₂O₃ | 6–13 |
| TiO₂ | 1–3 |
| H₂O | 8–16 |
| Other | 0.2–1.2 |
| FEATURE | |
|---|---|
| Colour: | Light to dark brown |
| Shape: | Accordion-shaped granule |
| Bulk density (a): | 64–160 kg/cu m |
| Moisture loss @ 110 °C (230 °F): | 4–10% |
| pH (in water): | 6–9 |
| Combustibility: | Non-combustible |
| MOH Hardness: | 1–2 |
| Sintering temperature: | 1150–1250 °C |
| Fusion: | 1200–1320 °C |
| Cation exchange capacity (b): | 50–150 me/100g |
| Specific heat: | 0.84–1.08 kJ/kgK 0.20–0.26 kcal/kgK 0.20–0.26 Btu/lb F |
| Water holding capacity (a): | 220–325% by wt 20–50% by vol |
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(a) Bulk density and water holding capacity vary with article size. (b) Exchangeable ions are Mg+2 and Ca+2, sodium acetate saturation / ammonium acetate substitution method. |
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