Electric poling behavior of polymethylmethacrylate

The electrically stimulated acoustic wave method for observing resident space charge in dielectric insulators has been used to characterize the poling behavior of millimeter-thickness samples of polymethylmethacrylate (PMMA) at temperatures from 40 to 90 degrees C with moderate applied fields. Heterocharge appears in the bulk of every sample tested, resulting in an apparent net increase of low frequency dielectric permittivity over time. In addition, a net internal charge was observed in some cases. This net charge was negative and located in the vicinity of the poling anode, and became most significant at 90 degrees C.>