Tuning Electrical and Dielectric Properties of Compatibilized PP/rPET/MWCNT Blend Nanocomposites by Manipulating Morphology through Mixing Sequence and Interfacial Reactions

Controlling the localization of conductive nanofillers in immiscible polymer blends is an established approach for the precise tuning of the multifunctional properties. The ultimate nanofiller localization and resulting morphology are governed by the interplay between thermodynamic driving forces and processing-induced kinetic effects, in particular, if an interfacial reaction is involved. In this study, multiwalled carbon nanotubes (MWCNTs) were incorporated into a polypropylene (PP)/recycled poly(ethylene terephthalate) (rPET) blend compatibilized using reactive PP- and rPET-based components. The localization of MWCNTs was controlled through a mixing sequence and in situ interfacial reactions. To better understand the effect of mixing sequence at the molecular level, several molecular dynamics simulations were performed, placing CNT at different initial locations in the blend and revealing a strong thermodynamic preference of CNTs toward the PET phase. Experimental investigations were conducted by employing two different mixing strategies to control the migration kinetics through processing. The masterbatch strategy was characterized by the initial dispersion of MWCNT into the PP phase, whereas the direct method involved mixing all of the components at once in the extruder. The results demonstrated that processing-induced kinetics and interfacial reactions can overcome the thermodynamic driving force and ultimately create a different final MWCNT localization. That is, interfacial reactions formed copolymers that blocked migration of MWCNT from the PP phase to the thermodynamically favorable rPET, and thus, the nanofiller accumulated at the interface.Nanocomposites prepared via a masterbatch method exhibited enhanced interfacial MWCNT networks, leading to improved dispersion, earlier rheological percolation, and superior electrical and dielectric performances compared to the direct processing method. The masterbatch-processed nanocomposites achieved a low electrical percolation threshold of 0.67 vol % (1.30 wt %) and a high electrical conductivity of 5.2 × 10–4 S/cm at 3 wt % MWCNT loading, indicating a seven-order-of-magnitude increase compared to the unfilled blend. This behavior arises from the preferential localization of MWCNTs at the interface and within the PP matrix, enabling the development of a 3D percolated conductive network. Below the electrical percolation threshold, the nanocomposite containing 1 wt % MWCNT exhibited an enhanced dielectric constant of 10, while maintaining a low loss tangent of 0.03 at 1 kHz. This dielectric enhancement is attributed to intensified interfacial polarization associated with well-dispersed, nonpercolated MWCNT networks. Overall, these results highlight that combining a processing strategy with reactive compatibilization provides an effective route to control nanofiller localization in recycled polymer blends, enabling the development of value-added nanocomposites for lightweight electronic applications.