Powders are also referred to as “divided solids” because they're basically solids that have been ground or disintegrated into smaller particles. They may either be granular or fine in texture, depending on the size of the individual particles.

These materials are used extensively in the food, cosmetics and pharmaceutical industries as well as in many others. In these industries, different powders are blended to compose the final product. The various component powders may have different particle sizes, powder flow properties and ability to blend smoothly with each other.

These properties may affect their packaging, volume and bulk. Such properties affect the caking, separation, segregation, irregular flow, flooding etc of powders. Hence, powder handling equipments and powder measurement and testing devices are an important part of industries. Powder rheometer is used to measure the flowability of powders in response to applied forces.

Properties of Powders

All powders have certain features in common. These features can broadly be classified into:

1. primary or fundamental characteristics regarding basic materials, particulate size, shape, surface area etc.
2. derived characteristics or behavioral properties like flow, bulk, tapped density, compactibility, lubricity etc.

Tapped Density

When it's required to assess the geometrical space occupied within the container, or envelope of a solid material, the true density of the powder is measured. This includes any cracks, pores, fissures etc. This is also called bulk density.

However, powder consists of particles with individual shapes and though the bulk density remains the same after grinding or processing, it's possible to increase the space occupied by the entire content by tapping or vibrating the container. This causes smaller particles to occupy the spaces between larger ones, and also changes the angles of the particles so that a more compact fit is achieved. This is known as tapped density. It is achieved without the application of any pressure and allows the powder to retain its flowability and consistency.

Why It is Important

The difference between bulk and tapped densities is in the way the powder is handled. When the powder is poured or passively filled into a container, the density is then termed as bulk density. Tapped density is obtained when the container is then lifted and dropped a certain number of times and the powder settles down more towards the bottom of the container.

A comparison between true density and tapped density is useful and powder handling equipments can then calculate the rate of flow, compressibility and powder-behavior under flow-conditions. Accurate powder measurement is important from the point of view of estimating packaging requirements and storage needs.

Author's Bio: 

Granutools offering best powder handling equipment, powder density, quality powder flow measurement & compressibility index tools. we offer a unique set of complementary instruments.