When subjected to heat, vermiculite has the unusual property of exfoliating or expanding into worm like pieces. This characteristic of exfoliation, the basis for many commercial uses of the mineral, is the result of the mechanical separation of the layers during the rapid conversion of contained water into steam. The increase in bulk volume of commercial grades is 8 to 12 times, but individual flakes may exfoliate as many as 30 times the original size. There is also a color change during expansion that is dependent upon the chemical composition of the vermiculite and the furnace temperature. The bulk density of crude vermiculite or vermiculite concentrate is in the range of 640-1120 kg/cubic meter. (40-70 lb/cubic foot) and exfoliated or expanded vermiculite is in the range of 64 - 160 kg/cubic meter (4 - 10 lb/cubic foot).
The size of vermiculite
|
size
|
Bulk specific gravity(kg/㎡)
|
Water absorption(%)
|
Thermal conductivity(k·㎡·h·°C )
|
Impurity(%)
|
|
5-10mm
|
70-100
|
500
|
0.045
|
3
|
|
4-8mm
|
70-100
|
480
|
0.045
|
3
|
|
3-6mm
|
80-120
|
465
|
0.045
|
3
|
|
2-4mm
|
80-120
|
465
|
0.045
|
3
|
|
1-3mm
|
80-150
|
420
|
0.045
|
3
|
|
20-40mm
|
100-180
|
410
|
0.045-0.055
|
2
|
|
40-60mm
|
100-180
|
400
|
0.045-0.055
|
2
|
|
80-120mm
|
100-180
|
400
|
0.045-0.055
|
2
|