Vermiculite

Exfoliated vermiculite is an inorganic, golden brown, ultra-lightweight aggregate ranging in particle size from 50 microns up to 30mm granules. The physical structure of the exfoliated granules is like a concertina, with a very high surface area and inter-laminar air spaces which give it excellent thermal insulation properties over an extremely wide range of temperatures up to 1260^oC and also excellent absorption properties It can be used in granular or free-flowing mixtures to carry high weight percentages of active chemicals and it is an ideal carrier or low cost filler for many compound formulations.

Source

The source of the mineral for the exfoliation of vermiculite is a naturally ocurring soft micaceous ore. This is mined and classified into grades, each having a specified range of particle sizes.

Manufacture

Exfoliation of the crude vermiculite is achieved by passing the ore through a furnace chanber where the resonance time is just sufficient to ensure exfoliation. This occurs at right angles to the cleavage planes, causing the flakes to expand into concertina-shaped granules. The granules are then evacuated from the chamber immediately, air classified, cooled and packed. Good exfoliation can only be achieved by a high rate of heat transfer and rapid generation of steam within the crude material.

Chemical Properties

Exfoliated vermiculite is an aluminium magnesium iron silicate. A typical composition of this material is:

Silicon (SiO₂)

37 - 40%

Magnesium (MgO)

21 - 29%

Aluminium (Al₂O₃)

6 - 10%

Iron (Fe₂O₃)

4 - 8%

Potassium (K₂O)

3 - 6%

Calcium (CaO)

1 - 4%

Carbon (CO₂)

1 - 2%

pH

7 - 10*

Organic Matter

nil

Moisture Content (when packed)

nil

* pH 7-10, but owing to the presence of associated carbonate rock impurities the reaction is normally alkaline.

The exchangeable cation normally present in vermiculite is magnesium. The cation exchange capacity is 90-100 milli-equivalents per 100 grammes. It is insoluble in water and relatively unreactive in an alkaline environment but is decomposed in strong acids leaving a residue of practically pure silica having a high degree of surface activity.

Physical Properties

The bulk density of vermiculite ranges from 60 to 120 kg/m³ depending on grade and exfoliation. Finer grades have a higher bulk density and an additional 10-15% increase in density should be allowed for under normal transportation and handling.

Reaction to Fire
Vermiculite is classified for reaction to fire as Class A1 in Decision 96/603/EC, as amended by Decision 2000/605/EC.

Grades

The standard grades normally available are:

Grade and Description Nominal Size (mm)

Vermiculite V0 Micron 0.1 - 1.0

Vermiculite V1 Superfine 0.5 - 2.0

Vermiculite V2 Fine 1.0 - 3.0

Vermiculite V3 Medium 2.0 - 5.0

Vermiculite V4 Coarse 5.0 - 15.0

Note: Nominal particle size indicates the 80% band i.e. up to 10% above of below the specified range.

Prices and Conditions of Sale

Prices are quoted on a volumetric basis, ex works plus haulage. All quotations give, orders placed. and materials supplied are subject to our Standard Conditions of Tradeng, a copy of which is available on request.

Packaging

Vermiculite is normally supplied in heavy duty non-returnable yellow plastic sacks holding a nominal 100 litres when packed. Alternative packaging is available on special order.

Supply

Vermiculite can be collected from our production unit at Gainsborough or delivered direct anywhere in the UK. A full vehicle load is 750 bags.

Free trial bags can be sent to any company in the UK in response to a written request indicating the type of application and potential usage if satisfactory. Technical information is also available for many applications and advice can be given on alternative bonding systems to make rigid shapes, etc.

Health and Safety
Click to download a copy of the Material Safety Data Sheet.