(37b) Electrostatic Charge Transfer Due to Single Impact of Pharmaceutical Powders

In processing of particulate solids, particle-wall and particle-particle collisions can generate electrostatic charges. This can lead to a variety of problems ranging from fire and explosion hazards to segregation, caking and blocking. For a fundamental understanding of the particle charging, it is essential to study the charge transfer due to single particle impacts on a target. We have designed and constructed a new experimental rig that can measure charge transfer due to a single impact between a particle and a target plane. In this study, pharmaceutical particles were tested by impacting against a stainless steel target. The amount of charge transfer due to impact can be described as a function of impact velocity and impact angle as well as initial charge. It is noted that for a given material, initial particle charge for which no charge transfer occurs due to impact is independent of impact velocity. This is viewed as a characteristic property which is related to the contact potential difference and tribo-electric series of the sample powders.