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2000
Conference Paper
Titel
Humidity Sorption in Subnanometer-Size Local Free Volumes of Polymides : A Positron Lifetime Study
Abstract
Positron annihilation lifetime spectroscopy (PALS) is used to study the local free volume in al polyimide 6FDA-ODA exposed to atmospheres of different relative humidity. The results support a model according to which water absorption in polyimides occurs in two stages. At RH < 30%, water is absorbed mostly in pre-existing sub-nanometer size local free volumes. At larger RH an increasing fraction of the sorbed water molecules will occupy sites other than pre-existing holes. A multiple occupation of larger holes by water molecules is discussed as a possible mechanism.
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