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Rheology pp 355-361 | Cite as

The Influence of Crystalline Structure on the Necking-Fracture Behaviour of Polyethylene

  • U. Gedde
  • B. Terselius
  • J. F. Jansson

Abstract

An anomaly in the necking and fracture behaviour of polyethylene under constant uniaxial tensile loading has been reported in several papers1–3. At a certain stress level, the almost instantaneous fracture of the neck formed at high loads was replaced by the formation of a neck that resisted fracture for a considerable time. This marked transition was observed for high density polyethylenes of comparatively high molecular weight. A hypothesis has been proposed to explain the appearance of the marked transition:
  1. 1.

    At high strain rates, large stresses concentrate to the taut tie chains between the crystallites, favouring fracture processes. At lower strain rates, the molecules rearrange in a way that distributes the local stresses more evenly over the structure which then deforms further rather than fracturing.

     
  2. 2.

    Owing to the high concentration of the chains in the high density, high molecular weight polyethylenes, the transfer of stresses and deformations between adjacent crystallites is very efficient. Therefore the structure has a good resistance towards fracture and the deformation of different lamellar regions occurs cooperatively.

     
  3. 3.

    The marked transition is a result of both (a) the rapid formation of high strength fibrillar structure, which is partly due to reasons given in item 2 of this hypothesis, and (b) the influence on the strength of the strain rate in accordance with item 1 of the hypothesis. At the marked transition, the maximum in the local strain rate is about the highest tolerable for the actual structure without macroscopic fracture. When an element of the specimen passes the maximum in local strain rate the probability for fracture of this element decreases due to the decreasing strain rate and to the continuous formation of a high strength fibrillar structure. In addition, e.g. the rise in local temperature in the neck caused by dissipation of deformation energy,may affect the necking and fracture behaviour.

     

Keywords

High Strain Rate High Density Polyethylene Lower Strain Rate Lamellar Thickness Macroscopic Fracture 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    U.W. Gedde and J-F. Jansson, Polym.Eng.Sci., 19: 77 (1979)CrossRefGoogle Scholar
  2. 2.
    U.W. Gedde and J-F. Jansson, to be published in Polym.Eng.Sci.Google Scholar
  3. 3.
    U.W. Gedde and J-F. Jansson, to be published in PoTym.Eng.Sci.Google Scholar
  4. 4.
    P.R. Swan, J.Polym.Sci., 54: 525 (1960).ADSCrossRefGoogle Scholar
  5. 5.
    G. Kanig, Co11.Polym.Sci., 255: 1005 (1977)CrossRefGoogle Scholar
  6. 6.
    B. Wunderlich, “Macromolecular Physics, Part 2”, Academic Press, New York (1976).Google Scholar
  7. 7.
    B. Wunderlich, J.Polym.Sci, Polym.Symp., 43: 29 (1973)CrossRefGoogle Scholar
  8. 8.
    J. Dlugosz, G.V. Fraser, D. Grubb, A. Keller, J.A. Odell and P.L. Goggin, Polymer, 17: 471 (1976)CrossRefGoogle Scholar
  9. 9.
    M.J. McCready, J.M. Schultz, J.S. Lin and R.W. Hendricks, J.Polym.Sci., Polym.Phys.Ed., 17:725 (1979)Google Scholar
  10. 10.
    J. Peterman, M. Miles and H. Gleiter, J.Macromol.Sci.-Phys., B 12: 393 (1976).Google Scholar

Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • U. Gedde
    • 1
  • B. Terselius
    • 1
  • J. F. Jansson
    • 1
  1. 1.Department of Polymer TechnologyThe Royal Institute of TechnologyStockholmSweden

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