Powder property change after passing through a feeder: The effect of electrostatics on powder flow

Powder feeding is one of the most critical processes in continuous manufacturing of powder-related products. Predictions of final product attributes have overlooked possible changes of powders properties as they pass through feeders and the effect has not been studied systematically. For example, the bulk density and the compressibility of the powder entering a continuous blender, have been assumed to be the same as the incoming raw materials. We find that this is not always the case. In this study, fourteen pharmaceutical powders were characterized both before and immediately after passing through a twin-screw feeder aiming to: (1) Quantitatively determine which materials alter their behavior. (2) Determine which properties are affected. (3) Investigate the probable causes of the changes in flow behavior (4) Validate the hypothesis that tribo-charging of the powder can be the cause of such behavior.