Charge Storage Performance of Polyetherimide Ultem~?1000—Influence of Secondary Antioxidants and Purification

摘要

The performance of a polymeric electretmaterial depends on many parameters, and besides chemi-cal structure, charging conditions, and application temper-ature, other factors, such as grade, manufacturer,processing history, and additive package, are critical.Commercial polyetherimide (PEI) Ultem~?1000 films exhib-ited satisfying electret properties as revealed by an isother-mal potential decay (ITPD) to 75 of the initial surfacecharge after 24 h at 90°C. It was found that after purifica-tion by reprecipitation this value drops to 34 and thatthe same PEI synthesized by two different methodsrevealed to be a very poor electret with charge retention ofalmost zero. Assuming that an additive in the commercial material might be responsible for this behavior, we identi-fied an organophosphonite which is commonly used asantioxidant in high-temperature polymers. We incorpo-rated this additive by melt compounding into purified PEIand found a dramatic increase in charge retention to 79of the initial charge at an additive load level of 0.5 wt .By immersing Ultem~?1000 films in water, the electretbehavior was further improved and almost 100 charge retention was achieved.