Simulation of fast space charge packets transport in polymers

The movement of space charge packets has been reported in polyethylene and epoxy resin under high electric fields by several groups, and has been characterized by the speed of propagation. A number of explanations of the formation and transport of slow space charge packets has been proposed. However, the mechanisms creating fast space charge packets are not clear. Dissado et al have suggested that the formation of fast charge packets is due to discontinuous electromechanical compression and charge injection at the electrode-insulation interface, and the transport of charge packets is related to corresponding relaxation processes. In that model, charges travel in packets because of group polarization. This paper gives an alternative model considering the reduction of charge carrier activation energy due to charge density triggered polymer chain movement and subsequent chain relaxation times. It is shown that the generation and transport of fast charge pulses are readily simulated by a bipolar charge transport model with three additional parameters: reduced activation energy, a charge density threshold, and a polymer chain relaxation time.