In this study, we fabricated conductive poly(vinylidene fluoride) (PVDF)/carbon composites simply by dispersing multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets into a PVDF solution. The electrical conductivity and the electromagnetic interference (EMI) shielding of the PVDF/carbon composites were increased by increasing the conductive carbon filler amounts. Moreover, we also found that the EMI shielding properties of the PVDF/CNT/graphene composites were higher than those of PVDF/CNT and PVDF/graphene composites. The mean EMI shielding values of PVDF/5 wt %-CNT, PVDF/10 wt %-graphene, and PVDF/CNT/graphene composite films with a thickness of 0.1 mm were 22.41, 18.70, and 27.58 dB, respectively. An analysis of the shielding mechanism showed that the main contribution to the EMI shielding came from the absorption mechanism, and that the EMI shielding could be tuned by controlling the films' thickness. The total shielding of the PVDF/CNT/graphene films increased from 21.90 to 36.46 dB as the thickness was increased from 0.06 mm to 0.25 mm. In particular, the PVDF/carbon composite films, with a thickness of 0.1 mm, achieved the highest specific shielding values of 1 310 dB cm/g for the PVDF/5 wt %-CNT composite and 1 557 dB cm/g for the PVDF/CNT/graphene composite, respectively. This was due to the ultrathin thickness. Our study provides the groundwork for an effective way to design flexible, ultrathin conductive polymer composite film for application in miniaturized electronic devices.

In recent decades, problems with electromagnetic interference (EMI) radiation problems have arisen, that can seriously reduce the performance of precision devices nearby and threaten human health. In consequence, it is...

Lightweight high-density polyethylene (HDPE)-graphene nanoplatelet (GnP) composite foams were fabricated via a supercritical-fluid (SCF) treatment and physical foaming in an injection-molding process. We demonstrated that the introduction of a microcellular structure can substantially increase the electrical conductivity and can decrease the percolation threshold of the polymer-GnP composites. The nanocomposite foams had a significantly higher electrical conductivity, a higher dielectric constant, a higher electromagnetic interference (EMI) shielding effectiveness (SE), and a lower percolation threshold compared to their regular injection-molded counterparts. The SCF treatment and foaming exfoliated the GnPs in situ during the fabrication process. This process also changed the GnP's flow-induced arrangement by reducing the melt viscosity and cellular growth. Moreover, the generation of a cellular structure rearranged the GnPs to be mainly perpendicular to the radial direction of the bubble growth. This enhanced the GnP's interconnectivity and produced a unique GnP arrangement around the cells. Therefore, the through-plane conductivity increased up to a maximum of 9 orders of magnitude and the percolation threshold decreased by up to 62%. The lightweight injection-molded nanocomposite foams of 9.8 vol % GnP exhibited a real permittivity of ε' = 106.4, which was superior to that of their regular injection-molded (ε' = 6.2). A maximum K-band EMI SE of 31.6 dB was achieved in HDPE-19 vol % GnP composite foams, which was 45% higher than that of the solid counterpart. In addition, the physical foaming reduced the density of the HDPE-GnP foams by up to 26%. Therefore, the fabricated polymer-GnP nanocomposite foams in this study pointed toward the further development of lightweight and conductive polymer-GnP composites with tailored properties.

As electronic devices become increasingly miniaturized, their thermal management becomes critical. Efficient heat dissipation guarantees their optimal performance and service life. Graphene nanoplatelets (GnPs) have excellent thermal properties that show promise for use in fabricating commercial polymer nanocomposites with high thermal conductivity. Herein, an industrially viable technique for manufacturing a new class of lightweight GnP-polymer nanocomposites with high thermal conductivity is presented. Using this method, GnP-high-density polyethylene (HDPE) nanocomposites with a microcellular structure are fabricated by melt mixing, which is followed by supercritical fluid (SCF) treatment and injection molding foaming, which adds an extra layer of design flexibility. Thus, the microstructure is tailored within the nanocomposites and this improves their thermal conductivity. Therefore, the SCF-treated HDPE 17.6 vol % GnP microcellular nanocomposites have a solid-phase thermal conductivity of 4.13 ± 0.12 W m K. This value far exceeds that of their regular injection-molded counterparts (2.09 ± 0.03 W m K) and those reported in the literature. This dramatic improvement results from in situ GnPs' exfoliation and dispersion, and from an elevated level of random orientation and interconnectivity. Thus, this technique provides a novel approach to the development of microscopically tailored structures for the production of lighter and more thermally conductive heat sinks for next generations of miniaturized electronic devices.

The electrical conductivity and the EMI shielding properties could be effectively tuned by the foaming degree.

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A microcellular structure can effectively tune the dielectric properties of PVDF/carbon composite foams.

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