Polyetherimides electrets

Figure 5 displays the ITPD curves determined at 90 °C of PEEK, PES, and PPS films [27]. Both sulfur-containing polymer films exhibit a pronounced charge drain-off within the first 180 min and hence cannot be considered as electret materials. PEEK, on the other hand, shows a moderate surface potential decay and maintains around 50% charge after 24 h at 90°C. The charge storage characteristics of commercial polyimides and polyetherimide (Ultem 1000) films at 90 °C are displayed in Fig. 6. Kapton HN (PI) films lose almost the complete surface potential within 24 h, exhibiting a steep decay in the first minutes. Upilex R renders better results, since its potential decay is moderate and after 24 h around 45% of the applied charge...

This review summarizes our work at the University of Bayreuth over the last few years on improving the electret performance of the commodity polymer isotactic polypropylene (Sect. 3) and the commodity polymer blend system polystyrene/polyphenylene ether (Sect. 4) to provide electret materials based on inexpensive and easily processable polymers. To open up polymer materials for electret applications at elevated temperatures we concentrated our research on commercially available high performance thermoplastic polyetherimide resins and synthesized several fluorinaled polyetherimides to identify structure-property relations and to improve further the performance at elevated temperatures (Sect. 5). 

As mentioned in the introduction, the commercial polyetherimide Ultem 1000 reveals the most promising electret behavior among the other high performance polymers investigated. However, a chemically identical polyetherimide synthesized... 

In Proceedings of powerMEMS 2004, Kyoto, pp 187-190 Bhrendt N (2010) Tailored processing methods for cellular polycarbonate and polyetherimide films - new potentials for electret and piezoelectric applications. IEEE Trans Dielectr Electr Insul 17 (4) 1113... 

---