ABSTRACT
In processing of particulate solids, electrostatic charges can be easily generated by particle-wall contacts. The charging process is often described as tribo-electrification or tribo-charging since sliding/ frictional contacts are invariably involved (Bailey, 1984). The particle charging is often a nuisance especially in particle handling processes, since an excess charge build-up can cause problems such as segregation, unreliable flow, explosion and fire hazards (Nifuku et al. 2003). Our current understanding is limited to a number of specific materials and lacks generality (Bailey, 2001).Therefore, it is of great interest to gain a better understanding of the tribo-charging of particles with a special focus on the role of material properties. The particle charging in an actual process, for example pneumatic conveying of powders, is of course of direct industrial interest, but difficult to analyse. It is far simpler and in fact essential for our fundamental understanding to study the charge generation due to a single impact by a single particle with a target plane. A number of such studies have been carried out with relatively large spherical particles of polymer materials (Matsuyama et al. 1994, 1995, 1997 & 2003; Matsusaka et al. 2001). For large particles, it has been shown that charge transfer due to normal impacts takes place during the unloading cycle and is
a function of contact radius (Matsusaka et al. 2001). In this work, it is intended to extend the experiments to smaller particle sizes.
