AbstractPoly(ethylene terephthalate) filament yarn has been annealed in nitrogen atmosphere, in silicone oil, or in nonreacting organic solvents. Morphological changes resulting from the annealing processes have been followed by Raman spectroscopy. Crystallinity, as evidenced by the width of the 1730 cm−1carbonyl stretching vibration, is shown to affect the macroscopic properties of these filaments. Furthermore, these spectroscopic results, together with shrinkage measured, suggest that the shrinkage and the crystallization processes in the polymer fiber proceed at different rates in different fluid medi
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