Dielectric Permittivity and Breakdown Strength of Thermally Aged Polypropylene/Ultra.High Molecular Weight Polyethylene Nanocomposites

This study investigates the effects of thermal aging on PP/UHMWPE blends and PP/UHMWPE/MgO nanocomposites. Thermal degradation of the aged materials is evaluated using thermogravimetric analysis, showing a reduction in the onset degradation temperatures for both systems. PP/UHMWPE/MgO demonstrates better thermal stability than PP/UHMWPE. Fourier transform infrared spectroscopy is employed to analyze the surface chemical modifications in the aged samples. The findings indicate the formation of carbonyl groups, with PP/UHMWPE/MgO displaying lower rates of oxidation compared to PP/UHMWPE. Relative permittivity increases with aging time, but the increase is less pronounced in the PP/UHMWPE/MgO. The presence of a dielectric relaxation peak at varying frequencies, with PP/UHMWPE exhibiting higher frequencies, is observed. AC breakdown strength gradually decreases with increasing aging time in both sample types, albeit to a lesser extent in the nanocomposites. Overall, the study demonstrates that the addition of MgO in PP/UHMWPE nanocomposites under thermal aging has a mitigated impact on thermal stability, oxidation reactions, dielectric permittivity, and AC breakdown strength when compared to PP/UHMWPE blends.