Development of polyvinylidene fluoride-graphite composites as an alternate material for electromagnetic shielding applications
05 Apr 2019-Vol. 6, Iss: 7, pp 075324
TL;DR: In this paper, a polyvinylidene fluoride (PVDF)-graphite composites were developed using solution mixing with uniform dispersion of micro-fillers within the PVDF polymer matrix for electromagnetic interference (EMI) shielding applications.
Abstract: Polyvinylidene fluoride (PVDF)-graphite composites have been developed using solution mixing with uniform dispersion of micro-fillers within the PVDF polymer matrix for electromagnetic interference (EMI) shielding applications. A conductive network of flake shaped graphite particles is formed within the PVDF polymer layers which improved the electrical conductivity of the composite thus providing promising EMI shielding properties. Conductivity of the composite increased by several orders of magnitude on graphite (80 wt%) incorporation in the PVDF (i.e. from 3.41 × 10−13 S cm−1 to 120 S cm−1). A high effective dielectric constant ( at a frequency of 8.2 GHz) has also been obtained for the PVDF-graphite composite having 80 wt% graphite. A high absorption dominated total shielding effectiveness value of ~98 dB has also been achieved at a frequency of 8.2 GHz for the above mentioned composite. The results are promising for using the PVDF-graphite composite as EMI shielding material in the X-band frequency.
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TL;DR: In this article, the influence of fillers on conductivity and interference shielding effectiveness in the frequency range of X-band (8-12 GHz) was investigated. But the authors focused on the microwave absorbing properties of conductive composites.
Abstract: Clean polyvinylidene fluoride scrap (rPVDF) from flexible oil pipelines was used as a matrix for the development of cost effective conductive composites. Carbon black (CB), expanded graphite (EG) and mixtures of both fillers were mixed with rPVDF in different compositions by melt processing. The influence of the conductive fillers on the electromagnetic interference shielding effectiveness (EMI SE) and microwave absorbing properties in the frequency range of X-band (8–12 GHz) was also investigated. Higher EMI SE was observed for the composite prepared with CB due to the higher conductivity. However, a synergistic effect was observed in both electrical conductivity and EM attenuation by reflection (reflection loss) by using hybrid materials. For composites containing 5 wt% of filler, that loaded with EG/CB (2:3 wt%) hybrid filler displayed higher attenuation of the EM (around 97%) at a frequency of 12.3 GHz. Increasing the CB in the hybrid, decrease the EM attenuation but the efficiency was observed in a broadband range, which is very important for stealth technology purpose. The influence of the fillers on the electrical, morphological and rheological properties of the composites was evaluated. Composite loaded with 7 wt% of the hybrid filler (EG/CB = 2:5 wt%) presented higher conductivity than that containing 7.5 wt% of CB but significantly lower viscosity, indicating outstanding processability. From scanning electron microscopy (SEM), it was possible to infer that the presence of CB in the hybrid promoted a better dispersion of EG, thus favoring the formation of the conducting pathway.
11 citations
TL;DR: In this article, graphite flakes with a lateral size greater than 50μm were used as filler for polyvinylidene fluoride (PVDF) composites, which showed an increase in the degree of crystallinity up to 25% by XRD and 43% by differential scanning calorimetry.
9 citations
01 Feb 2021
9 citations
TL;DR: In this article, the authors summarized the flexible and transparent properties of mainstream EMI shielding materials, and evaluated their potential as flexible and opaque EMI materials, including metal-based materials, MXenes, carbon-based and conductive polymers.
Abstract: The application of electromagnetic (EM) technology has greatly promoted the progress and development of society, and also brought the side effects of EM interference (EMI). In the fields of visualization windows, transparent wearable devices, and aerospace equipment, flexibility and transparency have become the performance requirements of EMI shielding materials. Materials such as metal-based materials, MXenes, carbon-based materials, and conductive polymers show the potential for flexibility and transparency and lots of cases have been developed. This article summarizes the flexible and transparent properties of mainstream EMI shielding materials, and evaluates their potential as flexible and transparent EMI shielding materials. Finally, the research progress of flexible and transparent EMI shielding materials based on different advanced technologies is summarized.
8 citations
TL;DR: In this article , a high-performance microwave absorber with simultaneously ultra-broadband microwave absorption, mechanical flexibility and high optical transparency is proposed, where a patterned indium-tinoxide (ITO) conductive metasurface is used as the upper surface resonance layer.
Abstract: A high-performance microwave absorber with simultaneously ultra-broadband microwave absorption, mechanical flexibility and high optical transparency is proposed. A patterned indium–tin–oxide (ITO) conductive metasurface is used as the upper surface resonance layer. ANSYS HFSS 15.0 was used for the infinite period structures of the absorber simulation, and the Floquet port, master-slave boundary condition and adaptive meshing were set in the software. As a result, the absorber features >90% broadband absorption, which covers a wide frequency range of 17.6 GHz (21.6-39.2 GHz) and includes part of the K and Ka frequency bands. What is more, the absorption is above 99% in the range from 30 GHz to 33.6 GHz. The optical transmittance of the absorber in the visible light band is 85%. The thickness of the absorber is only 0.1 times of the wavelength corresponding to the lowest absorption frequency (13.89 mm). Furthermore, the absorber maintains stable absorption at different incident and polarization angles due to the quadruple centrosymmetric pattern.
7 citations
References
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TL;DR: In this paper, a method is presented for determining the complex permittivity and permeability of linear materials in the frequency domain by a single time-domain measurement; typically, the frequency band extends from VHF through X band.
Abstract: In this paper a method is presented for determining the complex permittivity and permeability of linear materials in the frequency domain by a single time-domain measurement; typically, the frequency band extends from VHF through X band. The technique described involves placing an unknown sample in a microwave TEM-mode fixture and exciting the sample with a subnanosecond baseband pulse. The fixture is used to facilitate the measurement of the forward- and back-scattered energy, s21(t) and s11(t), respectively. It is shown in this paper that the forward- and back-scattered time-domain "signatures" are uniquely related to the intrinsic properties of the materials, namely, e* and ?*. By appropriately interpreting s21(t) and s11(t), one is able to determine the real and imaginary parts of ? and ? as a function of frequency. Experimental results are presented describing several familiar materials.
2,557 citations
TL;DR: In this paper, composites based on graphene-based sheets have been fabricated by incorporating solution-processable functionalized graphene into an epoxy matrix, and their electromagnetic interference (EMI) shielding studies were studied.
1,175 citations
TL;DR: The results indicate that single-walled carbon nanotube-polymer composites can be used as effective lightweight EMI shielding materials and are found to correlate with the dc conductivity.
Abstract: Single-walled carbon nanotube (SWNT)−polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15−20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied.
1,148 citations
TL;DR: In this paper, a review of recent developments in carbon nanofiber (VGCNF)/polymer conductive composites is presented, and the most significant properties of their composites compared to those of VGCNF/polymer composites are discussed.
988 citations
TL;DR: In this paper, a high-performance electromagnetic interference shielding composite based on reduced graphene oxide (rGO) and polystyrene (PS) is realized via high-pressure solid-phase compression molding.
Abstract: A high-performance electromagnetic interference shielding composite based on reduced graphene oxide (rGO) and polystyrene (PS) is realized via high-pressure solid-phase compression molding. Superior shielding effectiveness of 45.1 dB, the highest value among rGO based polymer composite, is achieved with only 3.47 vol% rGO loading owning to multi-facet segregated architecture with rGO selectively located on the boundaries among PS multi-facets. This special architecture not only provides many interfaces to absorb the electromagnetic waves, but also dramatically reduces the loading of rGO by confining the rGO at the interfaces. Moreover, the mechanical strength of the segregated composite is dramatically enhanced using high pressure at 350 MPa, overcoming the major disadvantage of the composite made by conventional-pressure (5 MPa). The composite prepared by the higher pressure shows 94% and 40% increment in compressive strength and compressive modulus, respectively. These results demonstrate a promising method to fabricate an economical, robust, and highly efficient EMI shielding material.
968 citations