This work describes the preparation of poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) (PET) composites using carbon nanotubes (CNTs)/graphene nanoplatelets (GNPs) hybrid fillers by melt blending process. The effects of CNTs/GNPs hybrid fillers on the thermal conductivity, electrical conductivity, electromagnetic interference shielding effectiveness (EMI SE) and mechanical properties of composites with varying CNTs/GNPs weight ratios were investigated. Scanning electron microscopy showed that the CNTs/GNPs hybrid fillers had better dispersion in PBT/PET matrix, they could effectively cooperate to build filler network structure. The excellent synergistic effects of hybrid fillers could significantly improve the mechanical properties and thermal conductivity. When adding 2 phr CNTs and 8 phr GNPs simultaneously, the thermal conductivity reached 0.84 W m−1 K−1 and Young's modulus was 1.2‐fold compared with PBT/PET blends. In addition, all hybrid composites with higher CNTs/GNPs weight ratios showed better electrical conductivity and EMI SE. The measurement of EMI SE and study of shielding mechanism indicated that absorption loss was the main mechanism for the attenuation of incident electromagnetic waves in hybrid composites over X‐band frequency.
Thermal annealing induced microstructure evolution and properties enhancement of polybutylene terephthalate/polypropylene/carbon nanotubes (PBT/PP/CNTs) nanocomposites was methodically investigated. The electrical conductive PBT/PP/CNTs nanocomposites with a low percolation threshold were obtained by simple melt blending due to the selective location of the CNTs in PBT phase and the formation of the double percolation structure. Thermal annealing further remarkably decreased the volume resistivity of the nanocomposites, with the maximum reduction of seven orders of magnitude. Scanning electron microscope observation and rheology tests demonstrated that the relatively large CNTs agglomerates were redistributed to build more homogeneous CNTs networks after annealing. The phase coalescence during annealing promoted the formation of the more perfect co‐continuous structure. These phenomena helped to enhance the electrical conductivity of the nanocomposites. Flexural properties of the nanocomposites were also enhanced after annealing, which might be due to the more effective stress transfer between the polymer and CNTs induced by the reconstructed CNTs networks. The nanocomposites obtained in this study possess excellent electrical and mechanical properties, which can be applied to the fields of sensors, electromagnetic interference shielding, anti‐static materials, and so forth.
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