Dielectric and thermal relaxations in amorphous and semicrystalline poly(ethylene terephthalate)
Undrawn PET was crystallized using several temperature programs to get samples of different crystalline structure, as indicated by a varying thickness of the amorphous layer between neighboring lamellae. The fluctuation model proposed by Donth was used to estimate the size (1–3 nm) of the cooperative, rearranging regions connected with the glass transition in these samples. There occurs a hindrance of the cooperative motions due to the crystalline structure, as shown by the correlation between the size of the cooperative, rearranging regions and the thickness of the layer of mobile amorphous material.
The WLF-curves are shown for the amorphous and the semicrystalline PET in the frequency range from 10−15 to 108 Hz. A deviation from these curves, expected for the hindrance, is not observed.
Key wordsSemicrystalline PET amorphous fraction glass transition cooperative motion characteristic length
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