CHARACTERIZATION OF UNIAXIALLY DRAWN POLY(ETHYLENE-TEREPHTHALATE) BY CP MAS C-13 NMR AND X-RAY-DIFFRACTION/

The phase structure of uniaxially drawn poly(ethylene terephthalate) ( PET) has been studied by CP/MAS C-13 NMR spectroscopy and X-ray diffra ction. CP/MAS C-13 NMR spectra show that the chemical shift values of the carbonyl and ethyleneglycol carbons of the non-annealed PET shift to high field as the draw ratio increases, but that the chemical shift values of the crystalline-peak for the heal-set PET shift to high fie ld as the draw ratio decreases. Experimental results suggest that the process of crystallization is affected by the semi-ordered structure i n the amorphous phase at the primary stage of the strain. These result s show that there are some structural differences between PET crystals of low-stretched films and high-stretched ones before annealing. (C) 1998 Elsevier Science B.V.