|Erhard, D.P.; Lovera, D.; Giesa, R.; Altstädt, V.; Schmidt, H.-W.: Influence of Physical Aging on the Performance of Corona-charged Amorphous Polymer Electrets, Journal of Polymer Science Part B: Polymer Physics, 48, 990-997 (2010) -- DOI: 10.1002/polb.21987|
The influence of physical aging on the electret properties prior to 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 non-aged PEI was improved by physical aging at 200°C for 4 d from 18 % to 95 % retained charge after 24 h at 120°C. A similar beneficial influence of physical aging on the charge storage capability was achieved using blends of PPE with PS.