Modulation of Charge Transport Property in Polypropylene Based on Magnetic Particles and Its Effect on Breakdown Performance

ABSTRACT Polypropylene (PP) is widely used in high‐voltage capacitors due to its advantages in insulation performance, processability, degradability, and recyclability. During long‐term operation, space charges are easily injected from electrodes into the dielectric under a strong electric field, inducing material degradation and even breakdown. Space charge suppression has long been a key issue in engineering applications. Different from the traditional technology route of space charge suppression by nano‐doping, a kind of novel physical method of regulating the charge migration path inside the dielectric by Strontium ferrite Magnetic Nanoparticles (SrFe 12 O 19 ) was proposed. The experimental results show that the oriented magnetic field generated by SrFe 12 O 19 can inhibit the free charge movement, reduce leakage current, and improve breakdown strength. Furtherly, PP/SrFe 12 O 19 composite was used as a functional layer to suppress carrier injection, a three‐layer structure (referred to as SPS) was constructed. When the mass fraction of SrFe 12 O 19 is 0.5%, the breakdown strength of the SPS rises to 283 kV/mm, which is 36 kV/mm higher than that of the PP. The leakage current at 100 kV/mm is 2.17 × 10 −9 A, decreasing about 81.8%. This work provides a new idea to solve space charge accumulation and improve the breakdown strength of DC capacitors.