One Molecule, Two Roles: Vitrimer-Enabled Polypropylene for High-Performance, Recyclable MWCNT Nanocomposites

Transforming post-consumer recycled polypropylene (PCR PP) into high-performance, recyclable vitrimer nanocomposites represents a major step toward sustainable polymer engineering. This study presents a scalable, catalyst-driven transesterification strategy using bis(2-hydroxyethyl) terephthalate (BHET, derived from depolymerized PET waste) and zinc acetate to generate dynamic covalent adaptable networks (CANs) within PCR PP. BHET serves a dual function: enabling dynamic crosslinking to form a robust vitrimer matrix and promoting efficient dispersion and interfacial adhesion of multi-walled carbon nanotubes (MWCNTs) through strong non-covalent interactions, supported by computational modeling. Although BHET can hydrogen-bond with itself, potentially reducing vitrimerization efficiency, this effect is suppressed in the presence of MWCNTs, as computational results confirm. The resulting nanocomposites show marked improvements in mechanical strength, thermal stability, and electrical conductivity at low MWCNT loadings. Rheological studies reveal enhanced melt strength and viscoelastic stability, while AC conductivity measurements indicate a well-developed conductive network. Thermal analyses demonstrate controlled crystallinity, with MWCNTs acting as effective nucleating agents. Importantly, reprocessing tests show excellent retention of properties, highlighting their suitability for circular-economy-driven applications. This work establishes a new paradigm for upcycling plastic waste into advanced, recyclable materials by uniting dynamic crosslinking with nanofiller reinforcement.