IDENTIFICATION AND QUANTITATIVE-ANALYSIS OF THE INTERMEDIATE PHASE INA LINEAR HIGH-DENSITY POLYETHYLENE

The observation of chain conformation and mobility in polyethylene by solid-state C-13 magic angle spinning (MAS) nuclear magnetic resonance (NMR) permits unambiguous identification and quantitative analysis of an intermediate phase. The carbon-carbon bonds in the intermediate ph ase adopt, on the average, an all-trans conformation and are more mobi le than in the crystalline state (room temperature rate of reorientati on approximate to 10(7) Hz). Comparisons of crystallinities by differe ntial scanning calorimetry, wide-angle x-ray diffraction, and NMR supp ort the high orientation of the intermediate phase and suggest a lower heat of fusion than for the crystals. Results from C-13 spin-lattice relaxation and H-1 spin diffusion show that the mass fractions are app roximate to 20% and the domain sizes approximate to 36 Angstrom. Both change with crystallization and annealing conditions. (C) 1994 John Wi ley and Sons, Inc.