Polypropylene (PP) has been increasingly investigated for use in high voltage cable insulation systems due to its superior electrical properties. Nevertheless, PP is too stiff and brittle, causing its difficulties to be extruded as cable insulation. Consequently, PP needs to be modified by blending with copolymers to enhance the flexibility of PP. Recently, many investigations have been carried out on the electrical properties of PP blended with ethylene-based copolymer (EBC) and propylene-based copolymer (PBC). However, the effects of thermal aging on the electrical properties of PP/EBC and PP/PBC blends are far from understood. Therefore, the current work investigates the effects of thermo-oxidative aging on PP/EBC and PP/PBC blends through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), breakdown, and conductivity analyses. The results show that PP experiences up to 10% degradation in breakdown strength upon aging. Nevertheless, blending PP with EBC mitigates breakdown reduction effects to merely 3% upon aging, while blending PP with PBC results in largely unchanged breakdown performance upon aging. These breakdown effects are correlated with changes in the microstructure and conductivity of the materials to gain insights into the structure-property relationships of the materials with respect to aging.
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