Aging Characteristics of PP Insulation Modified by SEBs Used for New Environment-Friendly High Voltage Cable

Polypropylene (PP) is a reliable insulation material to replace XLPE cable insulation. Due to its excellent electrical insulation properties, heat resistance and recyclability, it is an essential part of new environmentally friendly high-voltage cables. In the long-term operation process, the performance of the insulation material directly affects the service life of the cable. In this paper, the mechanical and electrical properties of PP insulation materials modified by styrene ethylene butylene styrene (SEBS) before and after thermal aging are studied. Firstly, PP and SEBS/PP samples are prepared by the plate vulcanization mechanism. Secondly, the two samples are subjected to artificial accelerated aging treatment in a 135° C oven for 7 and 28 days, and the mechanical properties are characterized by a universal testing machine. Finally, the electrical properties, such as volume resistivity and permittivity, of the samples before and after aging are characterized. The mechanical experimental results show that the elongation at break of aged PP at 28d is decreased by 65% compared with that of unaged PP, while that of SEBS/PP composite is decreased by 37.96%. The electrical experiment results show that the volume resistivity of PP aged for 7d is the highest, which is 3.2 × 1017 Ω ċ cm, while that of SEBS/PP aged for 28d is the lowest, which is 1.86 × 1016 Ω ċ cm. And the permittivity changes are not obvious. The experimental results shows that the comprehensive performance of PP and SEBS/PP is reduced after 28 days aging at 135° C. This work has important guiding significance for the research of insulation life of PP base high voltage cable.