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Effects of Annealing upon Molecular Orientation and Microwave Dielectric Anisotropy in Polyimide Films

Abstract

Molecular orientation and dielectric anisotropy of polyimide films before and after annealing for 2 h at 250°C were studied by use of the microwave method. The annealing made the dielectric constant ε′ and loss ε″ decrease markedly while gave a little change in the orientation pattern and then in the direction and degree of molecular orientation in the polyimide films. On the other hand, the direction of maximal thermal shrinkage corresponded to that in which the polyimide molecules are, on an average, aligned in the maximum dielectric loss and minimum transmitted microwave intensity. The results suggest that the orientation pattern reflects the thermal shrinkage and that the decrease in ε″ due to the annealing is ascribed to an increase in crystallinity of polyimide molecules in the amorphous region but gives a bit change in orientation of macromolecules.

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Osaki, S. Effects of Annealing upon Molecular Orientation and Microwave Dielectric Anisotropy in Polyimide Films. Polym J 29, 807–810 (1997). https://doi.org/10.1295/polymj.29.807

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Keywords

  • Annealing
  • Polyimide
  • Molecular Orientation
  • Dielectric Anisotropy
  • Microwave

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