Effect of crosslinking on the low-temperature relaxation behavior of polyethylene

The dynamic mechanical properties of polyethylene crosslinked by chemical methods and by electron irradiation were determined from 77°K to 250°K on an acoustic spectrometer at a frequency of approximately 50 Hz. Parallel stress-strain, swelling, and x-ray scattering experiments were also carried out to determine the degree of crosslinking and crystallinity. It is found that the effect of chemical crosslinking is to suppress the loss intensity of the γ relaxation in polyethylene while preserving the symmetrical shape of the loss curve without changing the temperature position. The effect of radiation crosslinking, however, also changes the symmetrical nature of the curves. Possible mechanisms of these observed changes are discussed.