Tunable electromagnetic interference shielding performance of polypropylene/carbon black composites via introducing microcellular structure

Electroless nickel coated carbon fibers (ENCF) were blended with acrylonitrile-butadiene-styrene (ABS) to prepare composites for electromagnetic interference (EMI) shielding. The effects of processing parameters, such as additives, temperature, and fiber loading amount, on EMI shielding effectiveness (SE) were researched. The thermal stability of EMI SE of ENCF/ABS composites was tested by heat treating composites in a drying oven at 60°C, and SE was measured at an interval of one week to consider the degradation of SE. The best SE of ENCF/ABS composites could be reached was 44 dB at optimum processing parameters. The thermal stability of ENCF/ABS composites for EMI shielding was steady without obvious degradation after 60°C heat treatment for five weeks. © 1997 John Wiley & Sons, Inc.

Conductive polymer composites have been utilized in the field of electromagnetic interference (EMI) shielding, albeit requiring a high concentration of conductive fillers to achieve desirable EMI performance. To address this issue and enable the creation of superior EMI shielding composites with reduced filler loadings, this study employed a pulsed magnetic field featuring an amplitude of 0.7 T, a pulse width of 10 μs, and a frequency of 100 Hz to align flaky carbonyl iron (FCI) in poly(dimethylsiloxane) (PDMS). This method resulted in an improved EMI shielding performance of the composites. The outcomes revealed that the pulsed magnetic field effectively controlled the orientation of the FCI, forming a conductive network structure, with the average orientation angle of the FCI reaching 69.3°. The aligned composites exhibited a significant improvement in EMI shielding effectiveness, with the enhancement effect reaching 37.53% and the EMI shielding effectiveness reaching 24.87 dB. Moreover, the flexible tensile properties of the aligned composites were superior to those of the unaligned composites, particularly the elongation at break, which reached 197.46%. The concordance between the theoretical analysis and experimental results affirms the efficacy of the microsecond pulsed magnetic field in enhancing the EMI shielding performance of composite materials. Ultimately, the high-performance, flexible electromagnetic shielding composite materials prepared in this study demonstrate potential for use in advanced electronic equipment.

Preparing lightweight and versatile products is the unremitting goal of industry to save resources and energy. Lightweight carbon fiber reinforced polypropylene (CF/PP) composite foams with high‐performance electromagnetic interference (EMI) shielding materials were fabricated by microcellular injection molding (MIM) technology. The average length and distribution of CF in CF/PP composite foams were examined. Thanks to the introduction of foaming process, the average CF length of composite foams was 33.98% longer than that of solids, which effectively enhanced the electrical conductivity and EMI shielding properties. The effect of shot size, gas content, and injection rate on the electrical conductivity and EMI properties was investigated. With melt shot size of 2/3 of the cavity volume, gas content of 0.5 wt% N2 and injection rate of 100 mm/s, optimal cellular structure of the composite material was obtained. The EMI shielding effectiveness (SE) reaches 36.94 dB, which is the highest value achieved by using MIM technology to the best of the authors' knowledge. In addition, the mechanical properties of cellular structure can still maintain good values, with the tensile strength and impact strength improved by 15.3% and 14.03%, respectively.

This work reportsthe preparation of graphene nanoplatelet (GNP)/multiwalledcarbon nanotube (MWCNT)/polypyrrole (PPy) hybrid fillers via in situchemical oxidative polymerization with the addition of a cationicsurfactant, hexadecyltrimethylammonium bromide. These hybrid fillerswere incorporated into polyurethane (PU) to prepare GNP/MWCNT/PPy/PUnanohybrids. The electrical conductivity of the nanohybrids was synergisticallyenhanced by the high conductivity of the hybrid fillers. Furthermore,the electromagnetic interference (EMI) shielding effectiveness (SE)was greatly increased by interfacial polarization between the GNPs,MWCNTs, PPy, and PU. The optimal formulation for the preparation ofGNP/MWCNT/PPy three-dimensional (3D) nanostructures was determinedby optimization experiments. Using this formulation, we successfullyprepared GNP/PPy nanolayers (two-dimensional) that are extensivelycovered by MWCNT/PPy nanowires (one-dimensional), which interconnectto form GNP/MWCNT/PPy 3D nanostructures. When incorporated into aPU matrix to form a nanohybrid, these 3D nanostructures form a continuousnetwork of conductive GNP–PPy–CNT–PPy–GNPpaths. The EMI SE of the nanohybrid is 35–40 dB at 30–1800MHz, which is sufficient to shield over 99.9% of electromagnetic waves.Therefore, this EMI shielding material has excellent prospects forcommercial use. In summary, a nanohybrid with excellent EMI SE performancewas prepared using a facile and scalable method and was shown to havegreat commercial potential.

A waste material which is collected from palm oil mill called POFA is used as cement replacement in plastering work to overcome electromagnetic interference issue.In the experiment, variables involved POFA admixture percentage (weight %), topcoat powder-to-binder ratio, water-to-binder ratio, latex agent content (weight%), particle size of POFA (µm) and curing conditions.The EMI shielding effectiveness (SE) is mainly dependent on all variables, especially POFA admixture percentage and particle size of POFA.A hybrid Taguchi design and flower pollination algorithm (FPA) method was used to optimize the best approaching high EMI SE based on experimental data.The experimental results found that plaster mortar can shield -23dB of electromagnetic wave (EMW) while using FPA method was shielded -24.68dB.The interaction model of EMI SE was derived from regression analysis and the truth found that the EMI SE is dependent on the water-to-binder ratio followed by latex agent content, particle size of POFA and curing conditions.From the FPA process, targeted EMI SE were suggested 30.012% of POFA admixture percentage, 0.3 of topcoat powder-to-binder ratio, 1.03 of water-to-binder ratio, 10% of latex agent content, 45µm particle size of POFA and air curing condition were optimal variables.

The aim of this study is to discuss the effect of moisture absorption on electrical conductivity and electromagnetic interference of the carbon fiber (CF) reinforced bioplastic composite. The composites were prepared by the hot press machine, and immersed in water for 20 and 40 days. The electrical conductivity measurements were carried out as a function immersed time. The electrical conductivity of CF with two layers is greater than that of one layer, because the electrical conductivity increases with increasing the volume filler of CF. The electrical conductivity slightly increases with increasing the immersion time. The EMI SE (electromagnetic interference shielding effectiveness) of the composite was examined with the frequency from 500 MHz to 2000 MHz. The EMI SE of the CF increases with increasing the content of the CF, and the EMI SE result of composite is around 50 dB to 60 dB. There is scarcely significant effect of orientation on composite on the EMI SE.

Electromagnetic asymmetric films comprise metal organic frameworks derived porous carbon for absorption-dominated electromagnetic interference shielding

Preparation and EMI shielding performance of epoxy/non-metallic conductive fillers nano-composites

Lightweight and flexible Ni-Co alloy nanoparticle-coated electrospun polymer nanofiber hybrid membranes for high-performance electromagnetic interference shielding

Wood‐derived carbon has great potential in building sustainable, lightweight electromagnetic interference (EMI) shielding materials. However, developing a straightforward method for fabricating materials that exhibit both high EMI shielding effectiveness (SE) and multifunctionality remains a challenge. Herein, the carbonized wood/epoxy/iron composite (C/EP/Fe) with hierarchical porous architecture is synthesized by encapsulating magnetic nanoparticles inside the conduits of wood‐derived carbon materials through via a simple two‐step process. Hot pressing is used to convert the conductive pathways, the inherent 3D honeycomb structure into a 2D grid. This structural transition, synergized with the magnetic nanoparticles, markedly enhanced the EMI SE. At a density of 392.26 mg cm −3 and a thickness of 1.05 mm, the C/EP/Fe‐4 achieved an EMI SE of 95.3 dB in the X‐band and allowed for tunable EMI shielding performance through adjustments in rotation angles. Furthermore, the material demonstrated shielding efficiency exceeding 99.999999% across the C‐K bands, with excellent EMI SE values consistently above 89 dB. In addition to its superior EMI shielding performance, the C/EP/Fe exhibited a suite of multifunctional properties, including rapid Joule heating, excellent thermal stability, flame retardancy, hydrophobicity, and reliable mechanical strength.

It is important but challenging to develop high‐performance electromagnetic interference (EMI) shielding materials with customizable structures, tailorable properties, light weight, and high‐efficiency EMI shielding effectiveness (SE). Herein, a facile approach is proposed to customize aramid nanofiber (ANF) based EMI shielding aerogels with pre‐designed architectures through ultra‐malleable ANF jellies. By precisely regulating the interfiber interactions between ANF and constructing a robust 3D skeleton, ANF jelly can be ‘kneaded‐frozen‐heated’ like dough to produce ultralight, elastic and porous ANF aerogels with special structures, such as aerogel sandwich, spring, fabric, etc. Benefiting from the interconnected porous structure, conductive fillers such as silver nanowires (AgNW) can easily cover the aerogel skeleton by dip‐coating to form highly conductive paths. With an ultra‐low loading (7.5 wt.%) of AgNW, a 5.2 mm‐thick AgNW/ANF aerogel exhibit an average EMI SE of 75.4 dB in the X‐band. Aerogels with additional functions can be customized according to the actual application environment. A customized sandwich aerogel with fire‐retardant outerlayer and EMI shielding interlayer can be used in high‐temperature environments. A flexible aerogel fabric as an EMI shielding gasket can effectively block wireless power transmission. This work provides a forward‐looking strategy for constructing high‐performance EMI shielding materials with tailored properties.

Interfused core-shell heterogeneous graphene/MXene fiber aerogel for high-performance and durable electromagnetic interference shielding.

As the automotive industry shifts toward electric vehicle (EV) architectures and autonomous driving systems, there is an urgent demand for multifunctional structural materials that offer both superior crashworthiness and high-frequency electromagnetic interference (EMI) shielding. While fiber-reinforced polymers (FRPs) facilitate lightweighting, their inherent brittleness and limited shielding capabilities often necessitate hybridization. This study investigates the synergistic integration of Ti-6Al-4V titanium alloy sheets and unidirectional carbon fiber plies in a 3/2 Fiber Metal Laminate (FML) configuration. To address interlaminar delamination and enhance functional performance, neat thermoplastic polyimide (PI) veils were incorporated as interleaves. The EMI shielding effectiveness (SE) of the fabricated FMLs was rigorously characterized in the X-band (8.2–12.4 GHz). Results indicate that the PI veil-integrated FMLs achieved a SE exceeding 30 dB, surpassing the industrial requirement for commercial electronic protection. The enhanced performance is attributed to the PI veil acting as a dielectric interlayer that facilitates multiple internal reflections between the conductive titanium and carbon fiber phases, thereby shifting the primary shielding mechanism toward absorption. Skin depth analysis further substantiated that the neat veil optimizes the electromagnetic interaction within the hybrid structure. This research demonstrates that Ti/CF FMLs interleaved with neat PI veils provide a robust, dual-purpose solution for next-generation automotive engineering, ensuring structural integrity while shielding sensitive autonomous systems from electromagnetic disruption.

Chapter 12 - Biomass-derived porous carbon for electromagnetic interference shielding

Electromagnetic porous lignocellulosic matrix composites: A green electromagnetic shielding material with high absorption efficient electromagnetic interference