Morphology-driven electromagnetic shielding performance of graphitic nanoparticles in segregated polypropylene nanocomposites via electromagnetic melt processing

Electromagnetic (EM) melt-processing has emerged as an innovative and energy-efficient strategy for the structuring of thermoplastic nanocomposites (TPNCs). In this study, polypropylene (PP)-based TPNCs were fabricated using different grades of graphitic carbon nanoparticles (CNPs) to yield electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE). The applied structuring methodology consists of a multiscale processing strategy that combines high-energy ball milling of polymer micro-pellets and CNPs, formulated powder compaction into green bodies, and EM-driven localized heating to produce the TPNCs. This enables the formation of highly segregated, percolated conductive networks at ultra-low filler loadings. The percolation threshold values for green bodies were significantly dependent on CNP morphology, ranging from approximately 0.50 wt% for low-aspect-ratio graphene nanoplatelets to around 1.0 wt% for medium-aspect-ratio carbon nanotubes (CNTs). Upon EM melt-processing, due to viscoelastic deformation of CNP networks, the resulting threshold values of the structured TPNCs were approximately 0.73 wt%, 0.50 wt%, and 0.74 wt% for low, medium, and high aspect ratios, respectively. High-aspect-ratio CNTs, despite exhibiting greater structural defects, achieved the highest EMI SE of 19.7 dB/mm at 10 wt%, demonstrating that morphology dominates over graphitic crystallinity in governing transport properties and electromagnetic performance. Statistical modeling via response surface methodology (R² = 0.9988) confirmed the predictive significance of the CNP morphology and the concentration responses. This work underscores the critical influence of filler architecture and EM-induced structuring in enabling a novel, scalable platform for multifunctional polymer nanocomposites with enhanced electromagnetic shielding capabilities, offering promise for next-generation aerospace, electronics, automotive, and defense applications.