An anomaly in the necking behavior of polyethylene, Part 3

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Abstract
Differential scanning calorimetry (DSC) measurements, polarized light microscopy and scanning electron microscopy (SEM) studies are reported on neck fibers formed by constant uniaxial tensile loading of polyethylene specimens at temperatures ranging from 298 to 353 K. The DSC measurements indicate that the temperature of the melting peak (Tpeak) of the neck fibers is closely related to the fibrilinity, i.e., the content of complete fibrillar structure, and that Tpeak and thus fibrillinity of the fractured neck fibers is sensitive to the nominal stress in the region of marked transition. A previously proposed hypothesis concerning the appearance of a marked transition in the necking/fracture behavior of high density and high molecular weight polyethylene is thereby supported. The polarized light microscopy showed a correlation between the zone length of the transformation from spherulitic to fibrillar structure and the previously reported distinctness in neck formation. The crystallinity determinations obtained from the DSC measurements and the SEM observations confirmed the suggestion previously made that the density decrease in the fractured neck fibers of a high density polyethylene with Mn = 21.6 × 103 and Mw = 199 × 103 is a result of void formation.

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