The influence of physical aging on the electret properties before corona charging of three amorphous polymers, polyetherimide (PEI), poly(phenylene ether) (PPE), and polystyrene (PS), as well as with blends of PPE and PS, was investigated. The degree of aging was monitored by determining the enthalpy relaxation Delta h using differential scanning calorimetry (DSC). The electret performance was evaluated by isothermal potential decay (ITPD) at elevated temperatures and by thermal stimulated discharge (TSD) measurements. It was demonstrated that physical aging below the glass transition temperature substantially improves the electret performance of amorphous polymers by reducing the free volume and thus hindering charge motion. As an example, the performance of nonaged PEI was improved by physical aging at 200 degrees C for 4 days from 18 to 95% retained charge after 24 h at 120 degrees C. A similar beneficial influence of physical aging on the charge storage capability was achieved using blends of PPE with PS. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 990-997, 2010