Tailoring the performance of polypropylene nanocomposites with hybrid fillers for high-voltage electrical applications

Crosslinked polyethylene (XLPE) is widely used in high-voltage insulating cable coatings; however, issues such as crosslinking by-products, incomplete or excessive crosslinking, and resulting surface defects limit its performance. Although polypropylene (PP) coatings reinforced with dielectric materials have been proposed as an alternative, their fragility remains a challenge. In addition, few studies have systematically investigated the simultaneous improvement of thermal, mechanical, and electrical insulating properties through hybrid nanofiller incorporation into PP matrices. This study introduces random-PP-based composites as promising alternatives with enhanced elasticity, tensile strength, thermal stability, and electrical insulation. Hybrid PP composites containing SiO₂, Al₂O₃, SiC, and MgO nanoparticles were prepared using a 60 cm³ internal mixer. Both discrete and hybrid nanofiller additions significantly affected composite performance. The melting temperature increased from 170.8 °C to 171.5 °C, while the decomposition onset temperature improved from 425.9 °C to 455.5 °C, indicating greater thermal resistance. Electrical volume resistance rose from 1.53 × 10¹⁵ to 38.70 × 10¹⁵ Ω·cm, and surface resistance reached 25.70 × 10¹⁵ Ω. The dielectric constant increased from 2.74 to 2.81, reflecting improved charge-storage capability. Although toughness decreased with nanofiller incorporation, Young's modulus increased from 2.64 to 3.00 GPa, particularly in highly loaded hybrid systems. scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses confirmed fracture-surface characteristics and nanoparticle dispersion. These results demonstrate that hybrid nanofillers effectively enhance the multifunctional performance of PP nanocomposites for next-generation high-voltage insulating materials.