|Frese, T.; Lovera, D.; Sandler, J.K.W.; Lim, G.T.; Altstädt, V.; Giesa, R.; Schmidt, H.-W.: Electret Properties of Polyetherimides: Influence of Water Content and Comparison with other High-Temperature Polymer Films, Macromolecular Materials and Engineering, 292(5), 582-587 (2007) -- DOI: 10.1002/mame.200600463|
In this comparative study, the charge storage performance of commercial high-temperature polymer films was evaluated and correlated with their chemical structure. Isothermal surface potential decay measurements after annealing periods at 90 °C revealed that amorphous polyetherimide (PEI) films showed the best charge storage behavior. Polyimide films showed reduced charge storage performance, whereas sulfur-containing polymer films are not suitable as electrets due to their fast charge decay. Additionally, the effect of water content in PEI films in the range of 0.02-0.79 wt.-% was studied. Increasing amounts of water decreased the charge storage properties proportionally, but only by a relatively smaller amount: the highest investigated water content of 0.79 wt.-% reduced the charge by only 30%.