Influence of Irganox 1010 on Space Charge Behavior in Thermal-Oxidatively Aged PP/Elastomer Blends

Polypropylene (PP) has been considered as a promising insulation candidate for high voltage direct current (HVDC) cables for its overall low cost and recyclable. To address its high stiffness limiting application in cable system, a propylene-based elastomer (PBE), DOW VERSIFY™ 2200 was introduced. However, the potential lifetime of blends was confirmed to be reduced dramatically, to only one quarter of that of pure PP. Based on this observation and the fact that antioxidants (AO) can improve the thermal stability, an AO has been introduced to investigate its influence on thermal-oxidative ageing in PP/elastomer blends. According to chemical changes characterized by Fourier-Transform Infrared spectroscopy, the AO reacts with oxygen initially on the sample surface and is assumed to be consumed up within 3 to 4 weeks at $150 ^{\circ }\mathrm{C}$ in a fan oven. The space charge accumulation behaviour was estimated by the pulsed electro-acoustic method, where a resultant charge peak brought by the AO can be observed resulting in the positive charge movement and negative charge accumulation near the cathode, as a function of the poling time. It has been found that the DC breakdown strength (BDS) shows an increase with ageing times until 4 weeks.