Powder Flow Properties - Important Considerations Powder Handling

Knowing the definite characteristics, behavior and Powder flow properties are of the utmost importance in various industries such as the pharmaceutical industry. This information is vital because it helps us to know the exact result, we will obtain in doing certain operations. For example, the complete and definite knowledge of powder flow properties helps us in different operations such as compression, transportation etc.

These powder flow properties can further be measured using various metrics. Some of the most popular and most useful properties which are used to predict the behavior of flow of powders are powder cohesion, the dynamic angle of repose, powder compressibility, Carr's index and Hausner ratio. Various instruments are used to measure and predict these properties accurately such as Powder Rheometer, Bulk density testers, powder flow testers and much more. Let us dive deep and get an overview of each of these properties.

1. Powder Cohesion

Powder Cohesion is defined as sticking together of particles of the same substance. The particles tend to collect together or attract each other. They exert attractive forces towards each other called the Wander Waal’s forces. This is an important factor that determines the powder flow. Another type of attractive force that the particles can exert is an electrostatic force. This property signifies how the powder will flow through hoppers. Too much attractive forces inhibit the flow.

2. The Dynamic Angle of Repose

There are two kinds of angles of repose that affect powder flow properties, static and dynamic angle of repose. Here we will consider the dynamic angle of repose.
Dynamic angle of repose is the angle observed when the powder particles are moving continuously downwards on an inclined slope. Different angles of repose exert different effects on the powder flow properties. Different angles are associated with the size of the particles present in the powder.

3. Powder Compressibility

This is yet again an important factor which determines the powder flow. The powder compressibility is the ability of particles present in the sample of powder to shrink or compress in volume when pressure is applied. In other words, a material’s compressibility is its bulk density/pressure relationship.

4. Wall Friction

The flowability of powder is also largely dependant on external factors such as the friction between the walls of the container they are flowing through and the particles of the powder. Wall friction affects the angle of the hopper and it is required to be designed keeping the wall friction in mind. Taking account of this property, the shape of the hopper is decided whether it will be shaped as a cone or a wedge because wall friction dictates the mass flow.

5. Powder Rheometers

These instruments are capable of measuring the shear, bulk and various above mentioned dynamic properties of a powder. The powder samples are analyzed for various different conditions like consolidated, conditioned or even in the fluidic state leading to a full exploration of various properties.

With the advent of sensitive instruments like Powder Rheometers, measuring the powder flow properties has become accurate. The knowledge of powder flow properties is very vital if we want our system to run at maximum efficiency