The Characterization of Poly (ethylene terephthalate) Fibers by High-Resolution Solid-State 13C NMR Spectroscopy

The phase structure of poly (ethylene terephthalate) (PET) fibers has been studied by CP/MAS 13C NMR spectroscopy. 13C spin-lattice relaxation measurements have revealed the existence of three components which are assignable to the crystalline component and two noncrystalline components with different molecular mobilities. By using the difference in 13C spin-lattice relaxation times of these components, the spectrum of the crystalline component has been obtained by CPTl pulse sequence. The resonance line of methylene carbons thus obtained can be resolved into two components with different line widths in terms of Gaussian curves. On the basis of the analysis of the distortion parameter for the crystal lattice, the sharp and broad components are ascribed to the ordered and disordered crystalline components, respectively. The degree of crystallinity of the PET fiber annealed at 150°C under tension has been estimated to be 0.39 by the lineshape analysis.