Determination of transition temperatures and crystalline content of linear, high‐molecular‐weight polyethylene by proton NMR spectroscopy

Decomposition of the proton NMR spectra of linear, high‐molecular‐weight polyethylene into a Gaussian function and a Lorentzian function is discussed in terms of the Wilson‐Pake two‐component method for an inhomogeneous system. The results of a Goldman‐Shen experiment indicate that spin diffusion does not strongly couple the two regions. The temperature dependence of the Lorentzian (mobile) fraction is fitted to a function derived from the relation of English and Zoller. The critical temperatures give estimates of thermal transitions: Tα = 328 (± 5) K and Tγ = 163 (± 4) K. The fraction of Lorentzian spins excited by the γ relaxation correlates with the amorphous content of the sample as determined by differential scanning calorimetry and x‐ray diffraction.