Stress Relaxation Study of Fine Structure of α-Loss Band of Branched Polyethylene

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Abstract
In order to clarify the effect of branching on the α-loss band in polyethylene, the shear relaxation modulus of samples with various degrees of branching is measured from 5 sec to 900 sec, between -90°C and 60°C. Two relaxations named α1 and α2 in order of ascending temperature are observed separately and reduced to master curves by the method of reduced variables. The activation energies for the α1- and α2-relaxations are ca. 26 kcal/mol, and 46 kcal/mol respectively. The activation energies and the shapes of the relaxation spectra for these relaxations are independent of the crystallinity and degree of branching. As the degree of branching increases, the relaxation strength for the α1-relaxation increases and that for the α2-relaxation decreases, while both relaxations shift to lower temperatures. These results are compared with the existing molecular theories.

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