PHASE-STRUCTURE OF UNIAXIALLY ORIENTED POLYETHYLENE FILMS AS STUDIED BY HIGH-RESOLUTION SOLID-STATE C-13 NMR-SPECTROSCOPY

High resolution solid state 13C nuclear magnetic resonance (n.m.r.) measurements have been made at room temperature for uniaxially oriented polyethylene films by setting the drawing direction parallel to the static magnetic field. Two sharp lines assignable to the crystalline and non-crystalline components appear at 11.8 and 32.6 ppm, respectively, indicating that this sample contains highly oriented crystalline regions and almost disordered non-crystalline regions. On the basis of 13C spin-spin relaxation time measurements and lineshape analyses, the non-crystalline line can be further resolved into two components, crystalline-amorphous interphase and amorphous component. The thickness of the interfacial component has been estimated to be ≈90 A ̊† † 1 A ̊ = 10-10 m, which is extraordinarily large compared with the values for the isothermally crystallized polyethylenes and the theoretical value. On the other hand, the crystalline resonance line is found to be composed of three components with different spin-lattice relaxation times. The origin of these components is also briefly discussed. © 1990.