Addition of fines for the reduction of powder charging in particle mixers

Experiments were carried out to study the effectiveness of fine powders as an additive on the reduction of electrostatic charge build-up for glass beads, polyethylene resins and starch powders in a mechanical shaking device. Four fine powders, carbon nanotubes (CNTs), Larostat 519, activated carbon and aluminum powders were tested on their effectiveness on charge reduction. It is found that particle size does have a significant effect on charge build-up of the bulk powder. The addition of small fraction of fine glass beads (150–170 μm) into coarse glass beads (210–300 μm) led to observable charge reduction, indicating that small particles added to large bulk powders can help reduce electrostatic charge build-up. Compared to other additives of larger sizes, CNT is a much more effective antistatic agent. Aluminum powder performed poorest among all additives tested. CNTs out-performed the commercial antistatic powder, Larostat 519, in reducing the charge generated by shaking action. Furthermore, better charge dissipation was observed at higher CNT contents. The experiment also revealed that conductivity alone was not a good indicator of antistatic capability because aluminum powder, despite having a good conductivity, performed poorly.