Interplay of Migration Kinetics and Hybrid MWCNT/GNP Architectures in Compatibilized PP/rPET Nanocomposites for Electrical, Dielectric, and EMI Shielding Applications

Processing-induced migration of conductive nanofillers plays a decisive role in governing the microstructure and multifunctional properties of polymer blend nanocomposites. In this study, the migration behavior of multiwalled carbon nanotubes (MWCNTs) was systematically controlled in compatibilized polypropylene (PP)/recycled polyethylene terephthalate (rPET) blends using a two-step mixing strategy combined with reactive compatibilization. By varying the masterbatch addition time at a fixed MWCNT loading of 1 vol %, the localization of MWCNTs within the rPET dispersed phase, blend interface, and PP matrix was effectively tailored. Morphological, rheological, and solvent-extraction analyses confirmed that early masterbatch addition promotes MWCNT migration toward rPET domains prior to complete interfacial reaction, whereas delayed addition restricts migration and confines MWCNTs within the PP matrix. The optimized blend prepared with a masterbatch addition time of 4 min exhibited a balanced conductive network and enhanced interfacial polarization, achieving an electrical conductivity of 5.3 × 10 –5 S/cm and an average electromagnetic interference (EMI) shielding effectiveness of 8.1 dB. Increasing the MWCNT concentration to 3 vol % further enhanced the conductive pathway formation, resulting in an electrical conductivity of 7.4 × 10 –2 S/cm and an average shielding effectiveness of 21.3 dB, which satisfies the requirement for conventional EMI shielding applications. Furthermore, partial substitution of MWCNTs with graphite nanoplatelets (0.5 vol % MWCNT/0.5 vol % GNP) significantly improved dielectric performance, yielding a dielectric constant of 14.3 at 1 kHz (∼300% increase compared to the unfilled blend) while suppressing dielectric loss (tan δ ≈ 0.033). The improved dielectric behavior was attributed to the disruption of continuous conductive pathways and enhanced interfacial polarization induced by the hybrid nanofiller architecture. These findings establish a clear processing–structure–property relationship and demonstrate that controlling nanofiller migration and hybrid network architecture provides an effective strategy for tailoring the electrical, dielectric, and EMI shielding properties of recycled polymer blends for lightweight electronic and energy-related applications.