Abstract
The thermal behavior of amorphous poly-4,4′-oxydiphenylenepyromellitimide (du Pont H-Film) was studied by means of dynamic mechanical, dielectric, and calorimetric methods over a temperature range from –100[ddot] to 500[ddot]C. The heat capacity is a smooth monotonic function of temperature indicating the lack of any motion leading to transitions in this polymer. However, there are two distinct relaxation regions with maxima at 278[ddot] and 400[ddot]C (fmax 110 Hz). Activation energies obtained from the temperature dependence of the frequency of maximum dielectric absorptions were 25 and 43 ± 3 kcal/ mole for the two absorptions, respectively. These results are interpreted from a mechanistic point of view.

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