Some aspects of structural electrophysics of irradiated oriented LLDPE

In the case of the insulation polymeric materials, such as polyethylenes, it is of essential interest to understand correlations between structural changes and (di)electric properties. The dielectric behavior of unoriented (λ = 1) and oriented (λ = 5, 10, 15) linear low density polyethylene (LLDPE), irradiated to different absorbed doses of γ radiation (0, 100, 200, 300, 500 and 700 kGy), was studied through dielectric loss (tan δ) analysis. Dielectric relaxation behavior is related to the changes in the initial structure of LLDPE, induced by orientation and radiation processes, and compared with previous (dielectric relaxation and other) results on irradiated oriented low-density polyethylene (LDPE). Differential scanning calorimetry (DSC), IC spectroscopy and gel measurements were used to determine the changes in the crystal fraction, oxidative degradation and degree of network formation, respectively. Conclusions derived according to these methods were compared not only with changes in intensity and position of the molecular relaxations but also with changes in calculated activation energies for these dielectric relaxations.