Study of thermal oxidation in medium density polyethylene

Studies of thermal oxidation in a well-characterized medium-density polyethylene (MDPE) were performed using thermostimulated depolarization current (TSD) analysis, infrared (IR) spectroscopy and size exclusion chromatography (SEC). TSD spectra clearly indicate structural changes occurring during oxidation of the material. For the virgin samples, evidence for existence of only a weak α process were found, but the oxidation led, at its initial stage, to the appearance of both γ and β processes, whereas the intensity of the α process remained initially unchanged. The results of the other analyses show that the oxidation process takes place in the amorphous phase and results in a significant reduction of molecular mass, which is the main factor contributing to the embrittlement of the polymer. TSD also indicated creation of deep electronic states, possibly at the amorphous-crystalline boundaries