Bentonites:
Clays that contain 75% of montmorillonite as the primary clay mineral are called as Bentonite. They swell to a great extent in water due to the interlayer water adsorption tendencies. Following are few of the highlighted properties of this mineral.
1. Fine size of this mineral makes it very plastic
2. The mineral has very high base-exchange capacity
3. Has high green strength
Bentonites generally carries impurity traces of quartz, iron oxide, calcite and feldspar. The main drawback of the mineral is its very high drying shrinkage. It is due to this property that the Bentonite mineral is added in very small amounts in whiteware body. They are used in whiteware to increase the plasticity and thereby the workability and to increase the green and fired strength.
To be contd…
