Volume recovery measurements have been used to study the physical aging behavior of a polyetherimide. Isothermal aging temperatures near Tg were studied with aging times ranging up to several days. The volume decreases during physical aging and levels off at equilibrium. For comparison purposes, the 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. Hence, the data can be reduced by aging time-temperature superposition. The temperature dependence of the shift factors used to reduce the volume recovery data and the times to reach equilibrium for the volume recovery follow the WLF equation and agree within experimental error with the values from enthalpy and creep measurements obtained in previous work. However, the approach to equilibrium for volume appears to differ from that of enthalpy, with volume recovery being faster than the enthalpy recovery at short times.
|Number of pages||8|
|Journal||Journal of Polymer Science, Part B: Polymer Physics|
|State||Published - Apr 30 1997|
- Physical aging
- Volume and enthalpy recovery