ENTHALPY RECOVERY OF POLY(ETHER IMIDE) - EXPERIMENT AND MODEL-CALCULATIONS INCORPORATING THERMAL-GRADIENTS

Enthalpy recovery data on poly(ether imide) from differential scanning calorimetry (DSC) is fit using the Moynihan-Tool-Narayanswamy model o f structural recovery. A self-consistent phenomenological equation is used to describe the experimentally observed structure and temperature dependence of the relaxation time in both glass and equilibrium regim es. Temperature gradients in the DSC sample are calculated based on th e thermal diffusivity of the material and are, for the first time, inc orporated into the model calculations. When no thermal gradients are a ssumed, model parameters are found to vary with thermal history despit e the use of the self-consistent equation for the relaxation time. The re is also a discrepancy between experimental data and model calculati ons with respect to the shape of the DSC annealing peaks. Accounting f or the presence of thermal gradients in the DSC sample is found to aff ect; the values of the model parameters needed to fit the data. Howeve r, thermal gradients are unable to account far the thermal history dep endence of the model parameters or for the discrepancy between observe d and calculated shapes of DSC annealing peaks.