Enhancement of High‐Voltage DC Insulation Performance and Mechanical Properties in Polypropylene Nanocomposites with Silane‐Coated MgO

Abstract In this study, magnesium oxide (MgO) is introduced as an inorganic oxide filler to utilize polypropylene (PP) as an insulating material, and silane (SiO₂) coating is applied to the surface of the nanoparticles to simultaneously improve the insulating properties and mechanical properties in a high‐voltage direct current (HVDC) environment. First, MgO particles with an average particle diameter of ≈200–250 nm are surface‐modified by silane treatment (MgO@SiO₂) and compounded with PP matrix by biaxial melt compounding process. XPS and FT‐IR analysis confirmed the effective silane coating on the surface of MgO particles, while STEM‐EDX and XRM analysis visually demonstrated that the coated MgO@SiO₂ is uniformly dispersed inside the PP. In terms of mechanical properties, such as tensile strength, bending strength, and strain at break, the PP/MgO@SiO₂ insulation composites show superior results compared to neat PP and PP/MgO insulation composites, which are attributed to the increased interfacial affinity and improved filler dispersion due to the silane coating. In addition, the PP/MgO@SiO₂ sample exhibits the highest value for direct current breakdown dielectric strength (DCBD), confirming that it can realize stable insulation performance in a high field.