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

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 (SrFe₁₂O₁₉) was proposed. The experimental results show that the oriented magnetic field generated by SrFe₁₂O₁₉ can inhibit the free charge movement, reduce leakage current, and improve breakdown strength. Furtherly, PP/SrFe₁₂O₁₉ 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 SrFe₁₂O₁₉ 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 × 10⁻⁹A, decreasing about 81.8%. This work provides a new idea to solve space charge accumulation and improve the breakdown strength of DC capacitors.