The effects of gamma-irradiation as the accelerated degradation procedure were analyzed for the evaluation of material stability. Low density polyethylene, polypropylene and ethylene-propylene terpolymer were studied in formulations with SiO2 nanoparticles (2 and 5 wt%) or as neat materials. High energy irradiation (up to 100 kGy) has revealed a faster increase in the absorption of carbonyl band in comparison with the corresponding change in hydroperoxide band. The three studied materials present increased oxidation rates as the received energy transferred from incidental rays is enhancing, because the thermal regime of degradation depends on the structural characteristics, namely initial number of tertiary carbon atoms and unsaturation level. The fate of hydroperoxides as oxidation initiators is discussed.