The five types of cohesion forces

Powders are used in many industries. Think of pharmacy where an important part of the medicines exist or are made from powders. But countless powders are also produced in chemistry. In addition, many powders are used in animal feeds for both pets and livestock. This includes not only additives such as vitamins and minerals that are added, but also products such as grains and soy that form the basis for animal feed. Many powder properties depend on the interaction that takes place between particles. This mutual interaction results in different cohesion forces that determine the cohesive character of the powder. These forces also affect the functionality of the powder, including the flow properties of powders.

The degree of interaction between particles depends on the type of material, the moisture content, the size and shape of the particles and the external electric field. The type of cohesion force also depends on this. There are different types of cohesion forces, 5 of which are explained:

• Liquid bridging: arises from the release of liquid from the particles caused by melting, wetting or decomposition. Poor cohesion can break the bonds in the particles during processing.
• Fixed bridging: arises from crystallization, glass transition, melting and fusion of dissolved solids. It is a strong and stable force.
• Van der Waals force: interaction of small powder particles.
• Electrostatic Forces: interaction between statically charged powder particles.
• Mechanical locking: the particles adhere to each other due to irregular surfaces. This makes separation of particles more difficult. This is a weak force. An example where this force is cleverly applied is Velcro.