Several ethylene homopolymers and ethene/α-olefin-copolymers with crystallinities ranging between 85 and 12% were characterized by dynamic-mechanical measurements. The occurring relaxations were correlated to the crystallinity of the polymeric materials and to morphology. The α-relaxation, being attributed to interlamellar shear, was found to be around 60 oC with activation energies of about 120 kJ/mol in samples with more than 42% crystallinity. The β-transition shows a much greater variety among the different samples characterized. Its relaxation temperatures_x000D_ vary between .40 and 10 oC with activation energies between 200 and 400 kJ/mol. The α- and β-relaxation of several quenched samples with crystallinities between 63 and 42% were found to overlap, thus producing bimodal maxima and different activation energies from the Arrhenius plots. A separation of these overlapping relaxations was only possible by measuring the relaxations over a frequency range of more than three orders of magnitude.

Polyethylene Ethene-/α-olefin-copolymer Dynamic-mechanical Properties Activation Energy α-Relaxation β-Relaxation

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Determined as the difference quotient.
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