The physical properties of polyethylene, the material used in gas distribution pipes and fittings, are ultimately determined by the nature of the polymer molecules in the resin used for pipe manufacture. This relation between molecular structure and properties is based on the morphology formed in the polyethylene by a particular processing history. Model polyethylenes having a very narrow molecular weight distributions and well defined levels of short chain branching and long chain branching have been used to quantify the effects of mechanical behavior, especially those related to fracture. Tensile deformation of unnotched and notched samples was done to assesses the relevant tensile and fracture toughness parameters. It has been demonstrated that a critical molecular weight is required for the attainment of good ductility and fracture toughness. This critical molecular weight is increased by the presence of short and long chain branches. The J-Integral fracture toughness increases by a factor of 2.5 over the molecular weight range (M = 40000 - 100000) where tensile ductility is achieved. Those polymers with high strain hardening rates resist deformation due to stress concentration at crack tips and thus display increased fracture toughness.


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    Title :

    Structural basis of the mechanical properties of polyethylenes


    Additional title:

    Strukturbasis fuer die mechanischen Eigenschaften von Polyethylenen


    Contributors:
    Carr, S.H. (author) / Crist, B. (author) / Marks, T.J. (author)

    Published in:

    Publication date :

    1984


    Size :

    40 Seiten


    Type of media :

    Report


    Type of material :

    Print


    Language :

    English






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