Many industrial unit operations use solids in the form of powders and granules, but often also with small particles. During these unit operations, particles interact with each other and with the surface of a pipe or a vessel. When this occurs, the particles may become electrostatically charged. Electrostatic charging can have various advantages and disadvantages, which is why it is important to be able to determine: whether, to what extent, and under which conditions a product can be electrostatically charged.
An electrostatic charge is different compared to normal electric charges in the sense that no current is present in the system. Electrostatic charges are usually induced by the so-called tribo-electric effect, which is based on a contact and friction component. Each material has a certain position in the tribo-electric series, one of which is shown in the figure below. Depending on the position in the series against the position of another material with which it makes contact, electrostatic charges may build; this is called contact charging. Contact charging is initiated by two different types of materials that are in contact and are subsequently separated. One of the materials will become positively charged and the other material will become negatively charged upon separation. The total amount of charge that could be generated is a material property, depending on particle size and chemical composition.
At Delft Solids Solutions, we operate multiple setups to determine the electrostatic charging of powders. Using these setups, multiple phenomena could be investigated: (i) particle to wall interaction, where a powder material is charged upon contact with a certain wall material and (ii) particle to particle interaction, where a powder material is fluidised in a fluid bed setup and the total amount of charge acquired by the sample after fluidisation is quantified.
In this way, not only the extent of electrostatic charging but also the rate of electrostatic charging and its discharging can be quantified. Besides, when working under controlled conditions of temperature and relative humidity, also the impact of moisture in the air can be investigated. The latter also acts as a possible solution to suppress electrostatic charging from occurring or to facilitate discharging. This enables investigation the charging properties of a product as it is used in various unit operations and consumer applications.


- Powder Flow and Ring Shear Testing
- Unconfined powder flow testing
- Powder Caking by Uni-axial compact strength testing
- Powder stickiness measurement
- Heubach and EN 15051 dustiness analysis
- Attrition and abrasion of particles, granules and tablets
- Segregation testing of powders and solids
- EN 17199-4 Dustiness index and nano particles
- Oil Absorption Number analysis of carbon black
- Powder conductivity testing
- Tribo Electrostatic charging of powders