| sampling table | A device for taking a small powder sample from a large quantity by pouring the material through a series of divided chutes that successively reject 50% of the material flowing. |
| sand | Mineral particles in the size range 200 to 2000 microns. |
| sand, fine | Mineral particles in the size range 20 to 200 microns. |
| silt | Mineral particles in the size range 2 to 20 microns. (Mineral particles less than 20 microns are usually referred to as ‘clay’). |
| sliding friction | (See dynamic friction). |
| static friction | The friction value developed when resistance to slip is fully mobilised prior to relative movement taking place between the material and the contact surface. Note that friction is dependent upon both the nature of the bulk solid and its interaction with a specific contact surface. The magnitude of frictional resistance is then a function of the normal stress acting between the bulk material and the contact surface. See surface friction, co-efficient of friction, dynamic friction. |
| surface adhesion | The result of attractive mechanisms between a particulate solid and a contact surface. These will give rise to surface cohesion effects according to the frictional nature of the interface. See adhesion, cohesion. |
| surface cohesion | The resistance to slip offered by internal forces between a particulate solid and a contact surface, separate from any frictional effect due to a normal force acting on the surface. These forces may be generated by such effects as surface tension, in the case of a damp powder, electrostatic forces or molecular forces. The effect may be exacerbated by a negative void pressure differential with ambient pressure. See adhesion. Cohesion. |
| surface friction | (See static friction, dynamic friction). |
| tortuosity | A measure of the convoluted path followed by an element of fluid passing through the intensities of a packed powder bed. |
| volume, absolute | The volume of the solid matter after exclusion of all the spaces (pores and voids). |
| volume, apparent powder | (See apparent powder volume). |
| volume, powder | The apparent volume of a powder as measured under specific conditions. |
Glossary of Terms in Powder & Bulk Technology
3. Powder Properties
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