Electromagnetic Interference Shielding Effectiveness Research Articles

High entropy alloy reinforcement for superior electromagnetic interference shielding performance in carbon fiber‐reinforced polymer composites

AbstractThis study explores the enhancement of electromagnetic interference (EMI) shielding effectiveness (SE) in carbon fiber‐reinforced polymer (CFRP) composites through the integration of equatomic CoCuFeNi high entropy alloy (HEA) particles. Employing mechanical alloying (MA), CoCuFeNi HEA powders were synthesized, revealing a face‐centered cubic structure with crystallite and particle sizes of 14.7 nm and 11.62 μm, respectively. The integration of these HEA particles at concentrations of 5%, 10%, and 15% by weight into epoxy resin, followed by the fabrication of composites using the hand lay‐up technique. Detailed structural analysis of HEA particles confirmed the successful synthesis of equatomic HEAs via MA. Structural analysis of the HEA integrated composites revealed vacancy regions at 5% concentration, a uniform distribution at 10%, and particle agglomeration causing inhomogeneity and vacancies at 15%. The composites demonstrated significant improvements in EMI SE, with the 10% HEA sample showing superior performance compared to the other samples. Specifically, the 10% HEA composite achieved a peak SE of 73.09 dB at 4.72 GHz, attributed to the optimized distribution of HEA particles that enhanced electrical conductivity and reflective properties.Highlights CoCuFeNi HEA particles were successfully synthesized via MA. HEA particles were added to epoxy at 5, 10, and 15 wt% for composite fabrication. Voids were observed in HEA5, uniformity in HEA10, and clustering in HEA15. EMI shielding was assessed using VNA, SE, dielectric permittivity, and magnetic permeability. The HEA10 composite achieved peak EMI shielding, 73.09 dB at 4.72 GHz.

All-Polymer Composite Film with Outstanding Mechanical, Thermal Conductive, and EMI Shielding Performances.

Robust polymer-based composites with high thermal conductivity (TC) and electromagnetic interference shielding effectiveness (EMI SE) hold great promise for applications in rapidly developing electronics. Traditional composites containing inorganic fillers often suffer from increases in processing difficulty, density, and significant deterioration in mechanical properties. Herein, we report for the first time a flexible multilayered all-polymer composite of poly(p-phenyl-2,6-phenylene bisoxazole) (PBO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), featuring excellent mechanical strength of 203.9 MPa, in-plane TC of 21.9 W/mK, EMI shielding effectiveness (SE) of 44.2 dB, high-temperature stability, and flame retardancy. The excellent TC, mechanical strength, and flame retardancy of PBO, the remarkable EMI shielding performance of PEDOT:PSS, and the π-π stacking interactions between adjacent layers contribute to the comprehensive properties, which outperform most of the traditional composites of polymers and inorganic fillers reported so far. This full-polymer design may pioneer a new strategy for the preparation of robust and lightweight multifunctional composites.

Optimization of Electromagnetic-Wave Reflectivity Performance of Electromagnetic Shielding Yarn Prepared by Evaporation-Induced Sintering of Ga60.5In25Sn13Zn1.5 Alloy with Nanosilicates.

Electromagnetic interference (EMI) shielding textiles have received widespread attention, and liquid metal (LM) shows superiority in flexible and deformable electronics. Here, we introduce a novel method using nanosilicates to help sinter LM through capillary evaporation, resulting in strong adhesion to substrates. By adjustment of the amount of nanosilicates, flexible EMI shielding yarns are created using dip-coating and curing processes. The sintered LM tightly adhered to the undulating and uneven surfaces of polyurethane (PU) yarns. The as-fabricated ION/LM@PU ("ION" is abbreviation of "ionogel") has strong EMI shielding and low EM-wave reflection due to the high electrical conductivity of the LM layer and good impedance matching of P(AAm-co-AA) ionogel. The addition of an ionogel enhances EM-wave absorption and strengthens interfacial polarization, making it an effective green EMI shielding yarn for reducing secondary reflection pollution. ION/LM@PU exhibited high total electromagnetic interference shielding effectiveness (EMI SET) (∼56 dB), low reflected power coefficient (R) (∼0.153), high impedance matching (|Zin/Z0| ≈ 0.660), high tensile strength (∼23.75 MPa), and high elastic recovery (∼0.92 at 10th stretch-release cycle). The EMI shielding mechanism of ION/LM@PU ± 60° is composed of reflective loss and absorption loss (including multireflective loss, conduction loss, dipole polarization loss, and interfacial polarization loss).

Effect of printing parameters and triply periodic minimal surfaces on electromagnetic shielding efficiency of polyvinylidene fluoride graphene nanocomposites

Electromagnetic interference (EMI) shielding is vital in safeguarding electronic devices from the harmful effects of external electromagnetic signals, a critical factor in ensuring the reliability and functionality of these systems. EMI, originating from a myriad of sources, can range from causing temporary disruptions to catastrophic system failures and potentially harmful consequences. This study delves into the EMI shielding capabilities of 3D printed Polyvinylidene Fluoride (PVDF)-graphene Triply Periodic Minimal Surface (TPMS) structures, fabricated using Material Extrusion (ME) process. The focus on TPMS structures stems from their unique geometrical configurations, offering promising potentials in enhancing EMI shielding effectiveness. Four distinct TPMS topologies—gyroid, Neovius, diamond, and I-WP were explored, with each demonstrating varying degrees of shielding effectiveness. 3D printed solid samples showed an average specific shielding effectiveness (SSE) of 13dB cm3/g, and Neovius triply periodic minimal surface (TPMS) structure exhibited an average SSE of 94dB cm3/g. Absolute shielding effectiveness (SSE/t) for solid samples and Neovius TPMS structure is around 66dB cm2/g and 62.5dB cm2/g respectively. Among the tested samples, those with a Neovius topology emerged as particularly promising, exhibiting high EMI shielding effectiveness suitable for commercial applications. Furthermore, the study investigates the impact of several design and printing parameters, including relative density/infill percentage, print orientation, and the size of unit cells, on total shielding effectiveness (SET). Results revealed SET variations ranging between 25dB and 75dB, suggesting that tuning the SET of these samples is feasible by adjusting these parameters. The study's findings, highlighting a strong correlation between SET and frequency influenced by unique geometrical characteristics and frequency-dependent interactions, underscore the potential of architected PVDF-graphene TPMS structures in EMI shielding applications. This opens new avenues for research and development in this field, paving the way for more advanced and effective EMI shielding solutions.

Flexible and durable shape memory EVA/MXene/EVA fiber membrane for programmable EMI shielding

Flexible and lightweight electromagnetic interference (EMI) shielding materials are currently the focus of electromagnetic protection material research. By applying shape memory polymers to the field of electromagnetic shielding, intelligent electromagnetic shielding composites with programmable shielding performance can be prepared. In this study, a flexible EVA/MXene/EVA electromagnetic shielding composite membrane with programmable shielding effectiveness was prepared using electrospinning, vacuum filtration, and hot pressing techniques. Even with a low MXene content, the EMI shielding effectiveness in the X-band still achieved 40.5 dB, and the specific EMI shielding effectiveness was as high as 6.23 × 103 dB cm2 g−1. The composite membrane exhibited excellent shape memory performance, with a shape fixation rate (Rf) of 93.8 % and a shape recovery rate (Rr) of 92.1 %, achieving a programmable shielding effectiveness of 14.1–40.5 dB under 0–30 % tensile strain. Additionally, the composite membrane could serve as a switch for electromagnetic shielding, controlling the reception and shielding of electromagnetic waves. Simultaneously, the composite membrane exhibits excellent hydrophobicity, electrothermal conversion capability, and durability. Importantly, it retains almost the same shielding effectiveness even after undergoing 500 cycles of bending and folding, as well as prolonged exposure to strong acids and alkalis. This work not only offers new insights into the development of multifunctional and intelligent electromagnetic shielding composites suitable for harsh environments but also expands the application scope of shape memory smart materials.

Poly(Vinylidene Fluoride‐Hexafluoropropylene) Composites With Carbon Based Nanofillers for Electromagnetic Interference Shielding

ABSTRACTIn the current work, a series of flexible polymer matrix composites (PMCs) based on poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP) as the polymer matrix and carbon nanofillers, namely single‐walled nanotubes (SWCNT) or carbon blacks (CB), were fabricated via a facile preparation method of blending and solution casting. The electrical conductivity, morphology, dielectric constant, mechanics, and electromagnetic interference (EMI) shielding properties of the composite films were adjusted by varying the carbon type (CB = Ketjenblack, Vulcan, or SWCNT = Tuball) and amount (0.1–15 wt%). The influence of the conductive nanofillers on the EMI shielding effectiveness (SE) and microwave absorbing properties in the X‐band frequency range (8–12 GHz) were investigated. By increasing the carbon content, the EMI shielding properties of the composite films were improved due to an increase in the magnitude of the electromagnetic properties. As the loading of these carbon fillers approach the percolation threshold, the dielectric constant of the composite can dramatically increase because of the construction of a microcapacitor network. However, these nanofillers/polymer composites generally have high dielectric loss near the percolation threshold due to the direct connection between carbon nanofillers. The PVDF‐HFP/Tuball composite particularly contributed low dielectric loss to the electromagnetic (EM) wave, resulting in excellent microwave absorption properties with a SE per unit thickness of 337.5 dB/mm and 2.5× less weight compared with conventional aluminum with the same SE, demonstrating the promise of using these materials as practical EMI shields.

Revealing synergistic relationship of thermal conduction and electromagnetic shielding of reduced graphene oxide film

The present work tries to explore the evolution process of electro-magnetic interference shielding effectiveness and thermal conductivity of graphene film. There is an obvious promotion of electrical conductivity (from 3.51×10-3 to 769.20 S m-1) when GO is thermally reduced at 1100°C. Correspondingly, the reduced graphene oxide (rGO) achieves the highest EMI shielding effectiveness (∼54.84 dB) at 1100°C which is an synergetic result of electrical conductivity and porous structure with rich defects. The rGO is furtherly graphitized at 2800°C (G-rGO) to repair the defects and C-C network and then mechanically rolled to a densified film with bulk density of 1.64 g cm-3 (called as DG-rGO). The thermal conductivity of DG-rGO membrane increases to 720.56 W m-1 K-1 after graphitization and rolling. Porous structure and defects are beneficial to higher EMI shielding effectiveness while dense structure without defects lead to higher thermal conductivity. Therefore, the highest EMI shielding effectiveness and thermal conductivity cannot be obtained simultaneously. A reference range is provided to fulfill the request of EMI shielding and thermal conductivity.

Enhancement in the Electrical Properties and Electromagnetic Interference Shielding Performance of Acrylonitrile–Butadiene–Styrene/Carbon Nanotubes Foams via the Introduction of Bimodal Cell Structures

The cell structures of conductive polymer‐based composite foams significantly influence their electrical properties and electromagnetic interference (EMI) shielding effectiveness (SE), necessitating a thorough understanding of how these properties improve with evolving cell structures. In this study, supercritical CO2 foaming technique was manipulated to fabricate acrylonitrile–butadiene–styrene (ABS)/carbon nanotubes (CNTs) foams. The constant‐temperature mode was used to prepare unimodal foams (UF), while the bimodal foams (BF) were produced by varying‐temperature mode. The foaming properties, electrical conductivity, complex permittivity, and EMI SE of ABS/CNTs foams with various cell structures are methodically investigated at identical volume expansion ratio and CNTs content. The electrical conductivity of bimodal ABS/CNTs foam with CNTs content of 20% (BF‐C20) is 0.2191 S cm−1, higher than that of unimodal ABS/CNTs foam with CNTs content of 20% (UF‐C20) (0.1765 S cm−1) owing to the introduction of bimodal cell structures. Complex permittivity results manifest that at 8.2 GHz, the ε′ and ε″ of BF‐C20 are 67.7 and 74.5, respectively, which are higher than 57.9 and 52.9 of UF‐C20. Among all ABS/CNTs foams, the total EMI SE of BF‐C20 attains the highest EMI shielding value, which reaches 30.2 dB. Furthermore, the absolute shielding effectiveness of BF‐C20 is 188.5 dB (g cm−2)−1, which is 17.3% higher than that of UF‐C20.

Mechanically robust, self-healing and stretchable electromagnetic shielding materials based on multi-component dynamic bonded polyurethane elastomer

Stretchable self-healing electromagnetic interference (EMI) shielding materials can automatically restore their original performance after mechanical damage, and can still maintain over 20 dB EMI shielding effectiveness (EMI SE) under tensile state. In this work, a series of highly stretchable self-healing polyurethane elastomer PUBNS-X was prepared by introducing dynamic disulfide bonds, boronic ester bonds and boron-nitrogen coordination (B-N) on the polyurethane main chain. It was found that B-N coordination significantly increased the elongation at break and the tensile strength. The high dynamic reversibility of boronic ester, disulfide bond and B-N coordination bond synergistically endowed PUBNS-X with excellent temperature-triggered self-healing properties. The mechanical properties of PUBNS-X can be restored to more than 90 % at 60 °C. The pre-assembled silver nanowires (AgNWs) conductive network was then introduced into the polyurethane surface by taking advantage of the fluidity of the dynamically bonded polyurethane backbone to obtain a series of stretchable self-healing electromagnetic shielding composites (AgNWs/PUBNS-Y). The results showed that the EMI SE of AgNWs/PUBNS-Y can reach ∼55 dB, and the conductivity can be restored to 82 % of the original value after healing at 60 °C. The investigation of the electromagnetic interference shielding performance of composites under different strains showed that the EMI SE of AgNWs/PUBNS-3 can still maintain 20 dB under 90 % strain. These composites will have broad potential applications in the fields of flexible wearable electronic products, bionic intelligent materials and soft robots.

Highly stretchable and strain-insensitive multilayered electromagnetic interference shielding films prepared via a simple soaking-infiltration strategy

Stretchable electromagnetic interference (EMI) shielding films are crucial for wearable electronics. However, it is challenging to further endow the EMI shielding films with good stretchability and satisfactory EMI shielding effectiveness (EMI SE) under large strains. Herein, we successfully prepared high-performance stretchable polydimethylsiloxane (PDMS)/ single-walled carbon nanotube buckypaper (SWNT BP)/PDMS EMI shielding films with multi-graded conductive networks via a soaking-infiltration strategy. In this multilayered film, infiltration layers of SWNT/PDMS were particularly created between elastic PDMS and brittle SWNT BP. Owing to the multilayered structure and conductivity compensation effects arising from infiltration layers, our EMI shielding films exhibited excellent EMI SE of 34.2 dB with high stretchability of >400%. The outstanding EMI SE could be well maintained under large strains. At <50% strain, the relative change in EMI SE (|ΔSE/SE0|) remained consistently below 10%, while at even 100% strain, |ΔSE/SE0| was only ∼35%. Furthermore, we proposed a parallel-series hybrid model to describe electrical conduction in straining films. Due to their excellent conductivity under strain, the films could also serve as stretchable Joule heaters. This work provides a novel and simple approach for constructing strain-insensitive conductive films, with potential applications in stretchable EMI shielding and thermal management.

A Facile Method in Fabricating Flexible Conductive Composites with Large-Size Segregated Structures for Electromagnetic Interference Shielding.

To resist the plastic deformation of polymer particles during hot press molding, high molecular weights, and moduli are required for composites with segregated structures, thus the prepared composites exhibit poor flexibility. Also, larger particle sizes can bring lower percolation thresholds while the ensuing greater deformation destroys the conductive network. Moreover, segregated composites still face preparation complexities. Herein, a facile method for developing flexible composites with large-size segregated structures is proposed. First, silver-coated polydopamine-modified reduced graphene oxide (Ag@PrGO), as conductive fillers, is prepared by electroless plating. Next, polydimethylsiloxane (PDMS)-coated polyolefin elastomer (POE) beads are put into a bag containing the fillers. After a simple shaking, the fillers are adhered to the POE surface as the cohesive property of cured PDMS. Finally, flexible composites with large-size segregated structures are obtained via hot pressing. Benefiting from the 2D structure of the Ag@PrGO and the ability to slip, the conductive networks possess adaptable deformability. The prepared composites exhibit excellent electrical conductivity (203.55 Scm-1) at filler volume fractions of 3.4 vol%. The EMI shielding effectiveness can reach 70dB in the X-band at a thickness of 1.9mm and remains stable after bending and rubbing damage. This work paves the way for constructing large-size segregated structures.

A Durable Textile With Advanced Thermal Functions and Electromagnetic Shielding.

In the face of increasingly variable cold climates and diverse individual temperature regulation demands, personal thermal management (PTM) textiles with electromagnetic shielding have obtained significant attention. However, the PTM textiles face several challenges, including single heating mode, insufficient durability, and complex preparation processes. Herein, an all-day PTM textile Cotton@PDA/AgNPs (CPANS) with energy-free PRH, energy-saving solar heating, compensatory electricalheating, electromagnetic interference (EMI) shielding, and outstanding durability is fabricated by sequentially growing polydopamine (PDA) and silver nanoparticles (AgNPs) on the cotton fabric (CF). The CPANS exhibits low mid-infrared emissivity (36.6%) and high absorptivity (70.8%), which guarantees the energy-saving heating capability. Moreover, the conductivity of the CPANS is ≈11109Sm-1, enabling an electrical heating temperature of ≈177°C under a low voltage of 1.1V and superb EMI shielding effectiveness (≈60dB). The remarkable adhesive properties of the PDA ensure that the desired durability of the CPANS remains high even after rigorous physical treatments. This innovation shows enormous potential for wearable integrated garments in the future and offers a new ideal for PTM fabrics in the cold.

Flexible multifunctional composite films for adjustable EMI shielding behavior under self-fixed deformation

With the widespread application of electromagnetic technology, the significance of intelligent electronic devices in modern communication is increasingly prominent. Despite this, the public focuses more on the harm caused by electromagnetic pollution. However, traditional EMI shielding materials struggle to meet the diverse and dynamic application requirements. Hence, developing materials capable of adjusting EMI shielding has become imperative to satisfy various scenarios. This paper presents the composite film TAPU-MXene, which is capable of adjustable EMI SE under self-fixed deformation. Introducing tannic acid increases the innermolecular interactions of TAPU. This enhancement leads to remarkable improvements in mechanical performance, achieving a stress level of 36.6 MPa at a strain of 560 %. Furthermore, the catechol groups can establish non-covalent interactions with multiple substrates, endowing the TAPU film with remarkable adhesion and self-healing capabilities. By combining the highly conductive nano-filler MXene with TAPU, the EMI shielding composite film TAPU-MXene is obtained. The EMI SE of TAPU-MXene was up to 56.7 dB when MXene loading was 3 mg cm−2. Most importantly, TAPU-MXene exhibits the ability to adjust the EMI shielding effectiveness from 56.7 dB to 2.75 dB under self-fixing deformation through shape memory mechanism, demonstrating promising applications in the field of adjustable EMI shielding materials.

Pearl‐Inspired Colored Carbon Fibers with Electromagnetic Interference and Optical Camouflage Properties

Carbon fibers (CFs) are widely used in cutting‐edge and civilian fields due to their excellent comprehensive properties such as high strength and high modulus, superior corrosion and friction resistances, excellent thermal stability, light weight, and high electrical conductivity. However, their natural ultra‐black appearance is difficult to meet the aesthetic needs of today's civilian sector and the need for optical stealth in the military field. In addition, conventional coloring methods are difficult to effectively adhere to CF surfaces due to high crystallinity and highly inert surface caused by their graphite‐like structure. In this work, inspired by the nacre structural color of pearls, colored CFs with 1D photonic crystal structure are prepared by cyclically depositing amorphous (Al2O3 + TiO2) layers on the surface of carbon CFs through atomic layer deposition (ALD). The obtained CFs exhibit brilliant colors and excellent environmental durability in extreme environments. Moreover, the colored CFs also exhibit high EMI shielding effectiveness (45 dB) and optical stealth properties, which can be used in emerging optical devices and electromagnetic and optical stealth equipment.

Conductive Polyethylene/Polyester Textiles with Temperature‐Strengthened Electromagnetic Interference Shielding Efficiency

The advancement of electromagnetic interference (EMI) shielding materials provides reliable protection for the communication technology. However, the performance of conventional EMI shielding materials is significantly diminished in high‐temperature conditions. Herein, an efficient method is proposed to prepare conductive fabrics with temperature‐strengthened EMI shielding performance via chemical plating technique. The as‐prepared polyethylene/polyester‐metallized fabric (PMF) coated with Ni–W–P alloy exhibits outstanding EMI shielding effectiveness (SE) in X band, which is strengthened from 16 to 59 dB with temperature raising from room temperature to 130 °C. Particularly, the corresponding temperature‐strengthened shielding behaviors are investigated through simulations in Computer Simulation Technology. Additionally, PMF presents excellent corrosion resistance (corrosion voltage [Ecoor] of −0.324 V and corrosion current [Icoor] of −6.760 A·cm−2) and admirable Joule heating performance, reaching maximum temperature of 74 °C at only 1.5 V. Therefore, the as‐prepared PMF endows enormous potential in EMI protection under high temperature and harsh environments.

Design and development of low‐weight and high‐strength electromagnetic shielding nanocomposite in a microwave frequency range

AbstractIn this novel work, we fabricated the multiwalled carbon nanotubes (MWCNTs)/polypyrrole (PPy) nanocomposite by employing the novel ultrasonic dual mixing (UDM) method. Subsequently, the atomistics and structural characterizations of the fabricated MWCNT/PPy nanocomposite (PM) were performed using SEM, Raman, and XRD. Furthermore, we experimentally evaluated the mechanical properties of the fabricated PM by reinforcing the PPy matrix with MWCNTs at different wt.%. The experimental study of PM shows that the mechanical properties depend upon the amount and dispersion quality of MWCNTs in the PPy matrix. In order to validate the experimental outcomes, the conservative fully coupled finite element (FE) models were developed using the ANSYS Workbench and novel FEAST software. The electromagnetic interference (EMI) shielding effectiveness (SE) of developed PM was also calculated at different thicknesses of PM by taking the effect of SE due to absorption (SEA) and SE reflection (SER) in the microwave frequency range of the C‐band (5.37–8.2 GHz) into consideration. The total SE (SET), the cumulative sum of SEA and SER, is the strong function of the thickness of the PM. Additionally, our study's outcomes reveal that as the thickness of the PM increased, the SET also increased by dominating the SEA rather than the SER. The SET value of 75 dB was observed for a sample with a thickness of 3 mm, indicating a high level of shielding. Thus, material becomes a highly attractive option for achieving high‐performance EMI SE in the C‐band for satellite communications, Wi‐Fi devices, weather radar systems, surveillance, and cordless telephones. A complex permittivity and permeability were also studied using the Nicolson–Ross–Weir (NRW) method to understand the mechanism behind the EMI SE.Highlights Nanocomposite fabricated using the novel ultrasonic dual mixing method. FE models were developed to validate experimental results. The EC and EMI SE are improved with the increase in the sample thickness. Absorption, rather than reflection, dominated the shielding mechanism. SE was observed dB with good mechanical properties.

Ultrathin, flexible, and high-performance bacterial cellulose/copper nanowires film for broadband electromagnetic interference shielding and photothermal conversion

The swift advancements in wearable electronics, implantable medical devices, fifth-generation mobile communication, unmanned aerial vehicles, and military stealth technology have led to a surge in demand for highly flexible multifunctional films. Consequently, the enhancement of electromagnetic radiation and the requirement for normal operation in extreme environments have posed significant challenges for flexible electromagnetic interference (EMI) shielding films. In this paper, ultra-thin, flexible bacterial cellulose (BC)/copper nanowires (CuNWs) (BCu) films with Janus structure are prepared by the combination of microwave-assisted hydrothermal synthesis and vacuum filtration method, which can be used for broadband EMI shielding and photothermal conversion. BCu films demonstrate exceptional mechanical properties, boasting a tensile strength range from 48.5 to 77.3 MPa, accompanied fracture strain 4.1–5.9 %. When CuNWs mass in Janus film increases to 10 mg, the conductivity of BCu-4 Janus films can reach 4761.90 S cm−1. The ultra-strong EMI shielding effectiveness (SE, above 56.00 dB) is achieved in 6–26.5 GHz for BCu-4 film with an ultra-thin thickness (16 μm). Moreover, the specific EMI SE of BCu-4 is as high as 4294.38 dB mm−1. Furthermore, BCu Janus films exhibit outstanding photothermal conversion performance. A saturation temperature of BCu-4 Janus film reaches as high as 75 °C under irradiation of one sunlight (100 mW cm−2). The facile and collaborative strategy is provided for fabricating ultra-thin, flexible multifunctional Janus films with EMI shielding and photothermal conversion capabilities, addressing EMI problems in modern electronic technology and offering new avenues for applications in various fields.

Preparing efficient self-healing polyimide coating for enhancing stability of electromagnetic interference shielding film

Electromagnetic interference (EMI) shielding films were widely utilized in various electronic devices, but they were prone to damage and performance degradation in harsh environments. Therefore, it was urgent to maintain stable performance of EMI shielding films. In this work, we adopt the reactions between aldehyde-modified diamine monomers and dianhydride monomers with dynamic imine bond to successfully prepare a self-healing PI (SHPI) film. Benefit from dynamic imine and imide bond, the SHPI film possessed excellent thermal stability (T5 %=527.7°C), tensile strength (72 MPa) and self-healing efficiency (94.4 %). As protecting coating layer, the SHPI film was able to maintain the commercial aluminized polyimide (PI/Al) film with good EMI shielding performance in acid environment. The electromagnetic shielding film with self-healing coating still had average EMI shielding effectiveness value of 44.5 dB after exposed to 10 % concentration nitric acid solution for 30 min. It is noteworthy that when damaged by external forces, the electromagnetic shielding film with self-healing coating could achieve rapid healing, while the tensile strength was up to 87 MPa and the self-healing efficiency reached 92.5 %. This work provided an effective self-healing protective layer for EMI shielding material against corrosion in acidic environments and damage from external pressures.

Biobased recyclable epoxy composites reinforced with carbon nanotubes for electromagnetic interference shielding and Joule heating

AbstractCurrent epoxy thermosets are facing various challenges such as resource scarcity, environmental concern, and limited functionalities. Here, we present a novel solvent free approach to fabricate multifunctional carbon nanotubes (CNTs) reinforced biobased and recyclable epoxy thermoset composites through precuring in an internal mixer followed by curing in an oven. The epoxy matrix, a covalent adaptable network (CAN) based on dynamic imine bonds, was synthesized from entirely biobased feedstocks, including glycerol triglycidyl ether, vanillin, and 1,10‐diaminodecane. The shear force during precuring facilitated dispersion of CNTs in CAN matrix, allowing for high CNTs loading (up to 20 wt%). The well‐dispersed CNTs not only reinforced mechanical properties of CAN but also introduced new functionalities like electrical conductivity, electromagnetic interference (EMI) shielding capacity, and Joule heating performance. The composite with 20% CNTs exhibited a tensile strength and Young's modulus of 78.1 MPa and 3.07 GPa, respectively, marking a 34.2% and 63.6% improvement over pristine CAN. It also demonstrated a high electrical conductivity of 35.3 S/m, resulting in a remarkable EMI shielding effectiveness (22.8 dB) and excellent Joule heating performance (reaching 131.7°C at 27 V input). Furthermore, these composites are thermally and chemically recyclable due to dynamic imine bonds, promoting sustainability and circular economy.

Preparation and Characterization of Lightweight Carbon Foam Derived From Silicon‐Containing Arylacetylene Resin With Antioxidant Properties and Excellent Electromagnetic Interference Shielding Performance

ABSTRACTIn this study, carbon foam derived from silicon‐containing arylacetylene resin (CFPSA) was prepared by using silicon‐containing arylacetylene (PSA) resin as the carbon precursor and polyurethane (PU) foam as the organic sacrificial template. CFPSAs with diverse apparent densities were prepared through the simple impregnation of PU foam with PSA resin solutions of varying concentrations. Their structures, such as the pore morphology; chemical composition; thermal stability; compression properties, and electromagnetic interference (EMI) shielding effectiveness (SE), were characterized. The results indicate that with an increase in the PSA resin concentration, the skeleton of CFPSA becomes thicker, the pore size slightly increases, the apparent density increases, the compressive strength increases, and the EMI SE slightly reduces. CFPSA‐10's apparent density is 0.032 g/cm3, its 5% thermal weight loss temperature (Td5) in an air atmosphere is 642°C, its thermal conductivity is 38.1 mW/m K, its specific compression strength is 2.45 MPa/g cm3, and its specific EMI SE divided by thickness (SSE/t) is 2367 dB cm2/g. CFPSA exhibits lightweight and antioxidant properties, as well as excellent electromagnetic interference shielding performance, presenting great potential for application in aerospace and other fields.