Improvement of Polypropylene/Silicone Rubber Interface by Insulating Oils With Pressure Optimization

Cable accessory insulation system is inevitably affected by its interface states causing insulation failure. Insulating oils are often applied in the interface with a certain pressure to improve its performance, but the mismatching and degradation of polymer in insulating oils seriously affect the interface stability. This study focuses on polypropylene (PP) insulation and aims to improve its typical accessory interface with silicone rubber (SIR) by insulating oils with pressure. Results show that hydrocarbon oil has the biggest negative impact on PP with the most mass increment, more surface deposits, and significant deteriorating in both mechanical and electrical properties. By contrast, appropriate absorption of Si-containing oil helps modify surface and fill initial defects of PP, promoting insulating performance. Furthermore, it is found that interface pressure is conductive to fabricate a stable PP/insulating oil/SIR structure with excellent insulating performance. However, excessive pressure causes a negative impact due to interface deformation of materials. Based on the analysis of interface microstructure and the calculation of contact stress between metal electrode and polymer, the mechanism of coupling interaction among polymer, insulating oil, and external pressure is revealed. This research on the improvement of insulation interface can provide a key reference and basis for the manufacturing and optimizing of cable insulation.