37 巻 (2000) 10 号 p. 728-733
Impact electrification between fine particles and polymer film has been investigated both theoretically and experimentally. A powder, fly ash of 12μm in mass median diameter, was dispersed and accelerated in airflow, and then the particles were impacted on a target whose frontal surface was covered with a polymer film and the rear side was a metal plate. The films used were in the range of 25-250μm in thickness. The rear metal plate was grounded and the electric currents caused by impact electrification were measured by an electrometer. Two types of currents were detected, namely induced current and conduction current. The induced current was due to the charge accumulating on the film, while the conduction current was due to the dielectric breakdown arising from the particle impact. Using a film with small artificial holes, conduction current was detected. This fact shows that insulating material can be utilized as an effective charging wall as long as the charge accumulation in the material is well suppressed.