Microstructure and properties of poly(butylene terephthalate)/poly(ethylene terephthalate) composites based on carbon nanotubes/graphene nanoplatelets hybrid filler systems

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. In poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) (PET)/carbon nanotubes (CNTs)/graphene nanoplatelets (GNPs) composites, the filler network structure originates from the bridging between CNTs and GNPs which leads to a synergistic effect in the improvement of thermal conductivity. The composites with electrical conductivity generate conductivity loss, the interface between fillers and polymer matrix will cause interface polarization loss, and the GNPs interlayer can cause multiple reflection loss. These losses are the reason why the composites have shielding effectiveness.