https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/130693/1/j.ces.2010.07.005.pdf

Triboelectric charging of powders: A review

Electrostatics of particles

Impact electrification between an elastic sphere and a metal plate has been studied experimentally. To find out how charge transfers between the contact bodies, the voltage profiles at the impact are measured under various experimental conditions using a digital oscilloscope, and simultaneously the contact deformation of the sphere is visualized with a high-speed camera. The initial charge on the sphere and the transferred charge are obtained from the integrated voltage with respect to the elapsed time of the impact process. The variation of the electrification by repeated impacts is analysed by taking account of the initial charge and charge relaxation with elapsed time. Furthermore, the relationship between the transferred charge and the contact area as a function of the impact velocity is investigated based on the electrification theory and Hertz analysis of elastic contact deformation.

https://iopscience.iop.org/article/10.1088/0022-3727/33/18/316/pdf

Electrification of an elastic sphere by repeated impacts on a metal plate

http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/194296/1/j.ijpharm.2006.11.005.pdf

Triboelectrification of pharmaceutical powders by particle impact

We study the effect of humidity on the charge accumulation of polymer granulates shaken vertically in a stainless steel container. This setup allows us to control the humidity level from 5% to 100%RH while performing automated charge measurements in a Faraday cup directly connected to the shaking container. We find that samples of approximately 2000 polymer spheres become highly charged at low humidity levels (<30%RH), but acquire almost no charge for humidity levels above 80%RH. The transition between these two regimes does depend on the material, as does the sign of the charge. For the latter we find a correlation with the contact angle of the polymer with only very hydrophilic particles attaining positive charges. We show that this humidity dependence of tribo-charging can be used to control segregation in shaken binary mixtures.

/pdf/influence-of-humidity-on-tribo-electric-charging-and-4vlo5ksemh.pdf

Influence of humidity on tribo-electric charging and segregation in shaken granular media.

The contact potential difference of powder and the tribo-charge

The measurement and evaluation of the contact potential difference between various powders and a metal

Examination of the Contact-potential-difference Measurement Model between a Powder and a Metal

In order to design the toner particles of thermoplastic resin coated with charge contorl agents (CCA), a dry coating method was applied to its compounding process. Experiments were carried out with a high speed-high shear mill by changing operation time. The compound states of the particles obtained were evaluated by EPMA mapping analysis and other methods. Then a relation between the compound state and triboelectric charging was studied by investigating the variation of specific charge (charge-to-mass ratio) with the mixing time of composite particles and carrier.The results obtained are summarized as follows. The whole coating process can be divided into three regions. The variation of specific charge shows that the CCA-Coating fraction on the surface of core material influences both the maximum specific charge and the charging speed. A good correlation was recognized between the binding strength of CCA and the charge stability. Based on these facts, it is possible to design the CCA-coated thermoplastic resin particles which have more excellent triboelectric charging characteristics than the conventional particles obtained by kneeding and pulverizing.

Compounding of Thermoplastic Resin Powder-Charge Control Agent and Its Evaluation

In order to design the toner particles of thermoplastic resin coated with charge countrol agents (CCA), a dry coating method was applied to its complex formation. Experiments were carried out with a high speed-high shear mill by changing operating conditions. The compound states of the particles designed were evaluated by the measurement of lightness. The triboelectricity of the particles obtained were investigated by the Blow-off measurement of triboelectric charge in the case of mixing with magnetic material particles (Carrier).The results obtained are summarized as follows:1) It was found that the triboelectric charge of composite particles is maximum against operation time under each operating condition. The maximum was obtained at a shorter operation time under the condition of higher rotating speed of the casing and narrower gap between the inner piece and the casing.2) It was possible to represent a curve of the triboelectric charge vs. energy consumption despite various operating conditions. Then it was apparent that the triboelectric charge of the CCA-coated composite particles makes a maximum against energy consumption, and the maximum was obtained at about 2×106J/kg.Based on these facts, it is possible to design the CCA-coated composite particles which have excellent triboelectricity by the dry coating method, and to determine the optimum operating conditions.

https://www.jstage.jst.go.jp/article/sptj1978/31/7/31_7_483/_pdf

Takayuki Itakura

Papers

The contact potential difference of powder and the tribo-charge

The measurement and evaluation of the contact potential difference between various powders and a metal

Examination of the Contact-potential-difference Measurement Model between a Powder and a Metal

Compounding of Thermoplastic Resin Powder-Charge Control Agent and Its Evaluation

Compounding Operation of a Thermoplastic Resin Powder-Charge Control Agent and its Triboelectricity