Enthalpy, volume, and creep recovery measurements were used to study the physical aging behavior of a polyetherimide. Isothermal aging temperatures near Tg were studied with aging times ranging from 20 minutes to several days. Enthalpy and volume decrease during physical aging and level off at equilibrium, whereas creep curves are shifted to longer times during physical aging and become independent of aging time at equilibrium. For comparison purposes, the enthalpy and volume data are normalized to yield the departure from equilibrium which varies from unity at very short aging times to zero when equilibrium is reached. As the aging temperature decreases, the normalized curves are shifted to longer times without a significant change in shape, and thus, were reduced by aging time-temperature superposition. The shape of the reduced enthalpy and volume recovery curves appear to be different, with volume recovery being faster at short times. However, the two properties reach equilibrium at the same time within the accuracy of the measurements. The creep data was reduced by aging time-time and aging time-temperature superposition, and the times required to reach equilibrium for creep also agree within experimental error with those for enthalpy and volume.
|State||Published - 1996|
|Event||Proceedings of the 1996 Regional Technical Conference on Durability , Weatherability, and Aging of Plastics & Rubber - Akron, OH, USA|
Duration: Oct 28 1996 → Oct 29 1996
|Conference||Proceedings of the 1996 Regional Technical Conference on Durability , Weatherability, and Aging of Plastics & Rubber|
|City||Akron, OH, USA|
|Period||10/28/96 → 10/29/96|