CHARGE DYNAMICS AND MORPHOLOGY OF ULTEM-1000 AND ULTEM-5000 PEI GRADEFILMS

Polyetherimide is a versatile polymer with interesting thermal propert ies (T-g above 200 degrees C) that is already used in electrical engin eering. It is of interest to investigate its electrical charge storage and decay processes, both to predict the degradation occurring under electrical load, but also for the purpose of using it in electret devi ces. The difference between two similar grades of Ultem PEI films, whi ch have different charge decay processes, was studied. The more recent ly introduced grade, Ultem 5000, displays a charge decay which can be attributed to carrier drift. Ultem 1000 shows a slower decay process. Some microstructural effects, particularly related to the surface and its water absorption, may account for this important difference betwee n two very similar polymers. (C) 1998 SCI.