The influence of impact behaviors of polymers on electrification was investigated. We proposed the charging model of the polymer particles.First, impact charges of single polymer particle-metal plate and polymer particle-polymer plate were measured by an impact charging experiment in this study. In the case of impacts between the polymer-metal, it was concluded that the impact charge increased with vertical and horizontal impact velocities against the plate. On the other hand, the impact charge between the polymer-polymer depended only on that of the horizontal component. The results showed different charging mechanism between the polymer-metal and the polymer-polymer.Second, impact behaviors in the experiment were analyzed by means of finite element method (FEM) simulation in order to obtain the information concerning the impact from a microscopic point of view. The FEM results indicated that the particle was rotated and slid simultaneously during impact. It was also found that the particle always had a contact area larger than the plate. On the basis of experimental and simulated results, we proposed the charging model of the polymer particle.Third, we tried to confirm the validity of the proposed model by electrification of polypropylene particles in vibration fields, theoretically and experimentally. Calculated results by particle element method (PEM) simulation (in other words, distinct element method (DEM)) were in good agreement with the experimental results. Then, we estimated the charge of toner particles using this model. (C) 2003 Elsevier B.V. All rights reserved.