β Relaxations in polyethylenes and their anisotropy

Abstract
Measurements have been made of the anisotropy of viscoelastic behavior in specially oriented sheets of low‐density polyethylene. The results for the cold‐drawn sheets show a β relaxation process of very characteristic anisotropy. The annealed sheets show two relaxations in this region of temperature. The lower relaxation (about −10°C) is identified as an interlamellar shear process. The higher relaxation (about 70°C) has a very similar anisotropy to the β relaxation in cold‐drawn samples. Isotropic sheets of low‐density polyethylene have been also investigated. Two β relaxations are found in these materials.

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