Carbon Nanotubes Embedded in Nanofibrillated EPDM Rubber as Thermally and Electronically Conducting Polypropylene Nanocomposites for Flexible Electrostatic Discharging

Herein, we propose a hybrid approach for optimizing the carbon nanotube (CNT) dispersion in polypropylene (PP) nanocomposites based on both chemical functionalization and physical confinement. Our approach relies on a two-step scheme where CNTs are first functionalized and dispersed in an ethylene-propylene-diene-monomer (EPDM) rubber phase via solution mixing, followed by a second step where the CNT-reinforced EPDM phase is melt-mixed with PP and taken through the in situ fibrillation process. Morphological characterization supported by rheological analysis show that the CNTs are successfully confined and dispersed within an interconnected network of nanosized rubbery EPDM fibrils, distributed throughout the PP matrix. In addition to reducing the electrical and thermal percolation thresholds from approximately 1.5 to 0.25 wt %, this unique morphology brings significant improvement in the crystallization behavior of the PP nanocomposites, resulting in a more uniform crystallization behavior with both increased percent crystallinity and increased crystallization temperature compared to conventional PP/CNT nanocomposites. This morphology brings also significant improvement in the mechanical properties, raising both the tensile toughness and ductility by three times compared to conventional PP/CNT nanocomposites. All in all, our innovative morphology strikes an excellent balance between high electrical/thermal conductivity and high toughness and ductility presenting them as promising for flexible antistatic packaging and electrostatic dischargers.