Effect of phase-scale regulation on electromagnetic shielding effectiveness of co-continuous PP/PBT/CNTs composites

• Phase domain scale was refined during migration process of CNTs from PP to PBT. • 3 vol% CNTs was a relative saturation for the migration into PBT interior. • Double percolation and complex interfaces were formed in PP/PBT/CNTs composites. • Conductive percolation value of ∼ 0.19 vol% CNTs and EMI SE of ∼ 36 dB was achieved. • Incorporation of PP-g-GMA achieved a synergistical enhancement of composites. Herein, the carbon nanotubes (CNTs)-induced polymer-phase scale behavior was regulated in polypropylene/poly(butylene terephthalate) (PP/PBT) composites. To determine the effects of CNTs migration from the PP to the PBT phase on phase viscosity, morphology, and domain scale, PP/PBT/CNTs composites were prepared and systematically analyzed using experimental characterizations and numerical simulations. During composite preparation, the viscosity of both phases transited, the domain scale was refined from 3.1 µm to 1.8 µm, and interphase compatibility was significantly improved. When the CNTs content reached 3 vol%, the migration behavior became saturated. Furthermore, a co-continuous structure with double percolation, as along with more conductive pathways and complex interfaces, was formed in the PP/PBT/CNTs composites, leading to performance stabilization. Consequently, the prepared PP/PBT/CNTs composites exhibited a conductive percolation threshold of 0.19 vol% CNTs and an electromagnetic interference (EMI)-shielding effectiveness (SE) of ∼ 36 dB, accompanied by significant reflection and absorption losses. Furthermore, to further regulate phase morphology, compatibilizers such as maleic anhydride grafted PP (PP-g-MAH), glycidyl methacrylate grafted PP (PP-g-GMA), and glycidyl methacrylate‌ grafted polyolefin elastomer (POE-g-GMA) were incorporated, further confirming the correlation between phase-domain size and EMI-SE. Overall, this study demonstrates a strategy for designing eco-friendly nanocomposites with both ultralow percolation thresholds and excellent EMI-SE.