True Stress-True Strain Relationship in Uniaxial Extension of Oriented Specimen of Polyethylene

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Other Title
  • 配向ポリエチレンの1軸伸び変形における真応力-真ひずみ関係
  • ハイコウ ポリエチレン ノ 1ジク ノビ ヘンケイ ニ オケル シンオウリョク

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Description

The uniaxial deformation process of roll-oriented polyethylene sheet was analyzed by using the MIT equation which includes three parameters, c, σ* and ε*. The strain-hardening parameter, c, depends on the testing direction. This dependence increases remarkably with increasing initial orientation of the specimen, indicating the increased strain-hardening effect of tie molecules. The initial yielding stress, σ*, remarkably decreases with testing temperature, pointing zero stress at the melting temperature. At the testing angle of θ=45°, the σ* value takes the minimum owing to the maximum shear stress along the molecular axis in crystal. The critical ture strain value, ε*, at which each folded molecular chain in crystal takes an extended chain conformation in a hypothetical meaning, is independent of both the testing temperature and testing angle but only depends on the fraction of tie molecules, which increases with increasing draw ratio by rolling. The prediction that each tie molecule unfolds the tiny crystal part associated with it is supported by a great value of ε*=5.5 or draw ratio=240 in the case of single crystal mats of polyethylene which scarcely include tie molecules.

Journal

  • KOBUNSHI RONBUNSHU

    KOBUNSHI RONBUNSHU 32 (12), 724-732, 1975

    The Society of Polymer Science, Japan

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