Space Charge Behavior in Acrylic Elastomer Under DC Voltage With and Without Stress

For some applications of electroactive polymers (EAPs), the applied voltage has a dc component and space charge may accumulate and distort the local electric field in the dielectric. The space charge transport and accumulation are considered linking with critical dielectric properties, such as breakdown, polarization, and electrical aging. Few studies can be found in the literature related to the space charge characters in EAP materials. In this article, the space charge characters of a typical acrylic EAP, VHB 4910, are discussed and analyzed at different applied electric fields. The results show that even at an average electric field of 5 kV/mm, a large amount of heterocharge accumulation forms in front of the cathode, resulting in an obvious increase of the electric field near the cathode. After the large charge accumulation, a positive charge packet apparently moves toward the anode which is far different from the charge behavior observed in polyethylene and epoxy. Generally, prestrain enables larger electro-deformation in EAP, so the tests were performed on VHB 4910 with and without prestrain. The results show that a prestrain leads to an increase of the amount of heterocharge and the electric field distortion near the cathode. The strong enhancement of the local electric field may greatly influence the breakdown strength of the material. To further investigate the mechanism of the space charge transport property in VHB 4910, blocking layers were used to distinguish ionization from electrode injection and the space charge characters in multilayer structure samples are analyzed. It illustrates that ionization accounts for the main part of charge accumulation below 20 kV/mm, related to the “apparent backwards moving” of a positive charge packet.