ISSN:
1435-1536
Keywords:
Poly(ethylene terephthalate)
;
lamellar morphology
;
melting-recrystallization
;
annealing
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Structural changes occurring during crystallization of quenched amorphous poly(ethylene terephthalate) (PET) and subsequent cooling/heating cycles have been studied by real-time small-angle x-ray scattering (SAXS), using synchrotron radiation. Initial crystallization is found to occur by insertion of new lamellae between the existing ones, while rapid continuous melting/recrystallization happens when the cold-crystallized PET samples are heated above the previous highest annealing temperature. Such melting/recrystalization results in irreversible increases in the lamellar long period, the crystal thickness and the density difference between the crystalline and amorphous regions; in contrast, at temperatures below the prior highest crystallization temperature, the structural changes are dominated by reversible effects such as thermal expansion. However, throughout the entire temperature range up to the melting point around 250 °C, the crystal core thickness remains quite small, less than ca. 50 Å, and the linear crystallinity of lamellar stacks remains nearly constant around 0.3. Such a low crystallinity indicates the presence of thick order-disorder interfacial layers on the lamellar surface, whose thickness increases with temperature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00654164
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