Influence of Fe3O4 and Carbon Black on the Enhanced Electromagnetic Interference (EMI) Shielding Effectiveness in the Epoxy Resin Matrix

Sustainable development of bioepoxy composites reinforced with recycled rigid polyurethane foam for mechanical, thermal, acoustic, and electromagnetic applications in a circular economy approach

The accumulation of polyurethane (PU) waste presents a critical environmental challenge due to the inefficiencies of traditional disposal methods like landfilling and incineration. This study introduces a sustainable approach by repurposing 99.89% pure rigid polyurethane foam granules (~ 150 µm) as fillers (5 wt.%) in bio-epoxy composites, complemented with 99.89% pure vermiculite particles (~ 10 µm) at varying concentrations (2-10 wt.%). Comprehensive characterization techniques, including high-resolution scanning electron microscopy (HR-SEM) and Fourier transform infrared spectroscopy (FTIR), were employed to evaluate the composites' mechanical, thermal, electrical, acoustic, and electromagnetic interference (EMI) shielding properties. The study specifically measured EMI shielding effectiveness in the frequency range of 8-12 GHz. Among the formulations, sample S5 exhibited superior mechanical performance, with tensile strength (10.47 N/mm2), impact strength (0.006 kJ/cm2), and flexural strength (46.80 N/mm2). EMI analysis revealed a dielectric constant of 1.111 and shielding effectiveness of -35.24 dB, while sample S3 achieved optimal acoustic absorption (NRC 0.295). Thermal assessments showed the lowest thermal conductivity (0.141 W/mK) and a reduced burning rate (6.8 mm/min) for S5. These results highlight the viability of recycled PU foam-based composites in minimizing plastic waste and advancing net-zero carbon emission goals. Potential applications include battery enclosures, engine bay insulation, and cabin soundproofing in electric vehicles. This work establishes the novelty of integrating recycled materials into bio-epoxy matrices to address environmental challenges and create high-performance composites.

Advancements in electromagnetic microwave absorbers: Ferrites and carbonaceous materials

Heightened levels of electromagnetic (EM) radiation emitted by electronic devices, communication equipment, and information processing technologies have become a significant concern recently. So, substantial efforts have been devoted for developing novel materials having high EM absorption properties. This critical review article provides an overview of the advancements in understanding and developing such materials. It delves into the interaction between EM radiation and absorbing materials, focusing on phenomena like multiple reflections, scattering, and polarization. Additionally, the study discusses various types of losses that impact microwave absorber performance, like magnetic loss, and dielectric loss. Each of these losses has distinct implications for microwave absorbers' effectiveness. Furthermore, the review offers detailed insights into different microwave-absorbing materials, such as metal composites, magnetic materials, conducting polymers, and carbonaceous materials (composites with carbon fiber, porous carbon, carbon nanotube, graphene oxide, etc.). Overall, it highlights the progress achieved in microwave-absorbing materials and emphasizes optimizing various loss mechanisms for enhanced performance.

Ballistic and Electromagnetic Shielding Properties of Epoxy Resin Reinforced with Carbon Black and Jute Fabric

This study explores the development of a multifunctional composite material by incorporating carbon black (CB) into an epoxy matrix reinforced with 30 vol.% jute fabric. The objective was to evaluate the impact of CB on the composite's tensile properties, ballistic performance, and electromagnetic shielding effectiveness (SE) within the X-band frequency range (8.2-12.4 GHz). The epoxy composite with 30 vol.% jute and 5 vol.% CB (EJ30/CB5) exhibited 15% improvements in its tensile strength and elastic modulus compared to the epoxy composite with 30 vol.% jute (EJ30) only. Ballistics tests indicated no significant increases in absorbed energy or limit velocity, which may be attributed to the structural rigidity introduced by the CB. An electromagnetic shielding analysis revealed that the CB addition significantly enhanced the SE from ~2 dB in neat epoxy to 5-8 dB in EJ30/CB5, with absorption emerging as the primary shielding mechanism. The findings highlight the potential of CB- and jute-reinforced epoxy composites for applications requiring both mechanical robustness and electromagnetic interference shielding.

Experimental Correlation of the Role of Synthesized Biochar on Thermal, Morphological, and Crystalline Properties of Coagulation Processed Poly(1,4-phenylene sulfide) Nanocomposites

This work aimed to study the thermal and crystalline properties of poly (1,4-phenylene sulfide)@carbon char nanocomposites. Coagulation-processed nanocomposites of polyphenylene sulfide were prepared using the synthesized mesoporous nanocarbon of coconut shells as reinforcement. The mesoporous reinforcement was synthesized using a facile carbonization method. The investigation of the properties of nanocarbon was completed using SAP, XRD, and FESEM analysis. The research was further propagated via the synthesis of nanocomposites through the addition of characterized nanofiller into poly (1,4-phenylene sulfide) at five different combinations. The coagulation method was utilized for the nanocomposite formation. The obtained nanocomposite was analyzed using FTIR, TGA, DSC, and FESEM analysis. The BET surface area and average pore volume of the bio-carbon prepared from coconut shell residue were calculated to be 1517 m²/g and 2.51 nm, respectively. The addition of nanocarbon to poly (1,4-phenylene sulfide) led to an increase in thermal stability and crystallinity up to 6% loading of the filler. The lowest glass transition temperature was achieved at 6% doping of the filler into the polymer matrix. It was established that the thermal, morphological, and crystalline properties were tailored by synthesizing their nanocomposites with the mesoporous bio-nanocarbon obtained from coconut shells. There is a decline in the glass transition temperature from 126 °C to 117 °C using 6% filler. The measured crystallinity was decreased continuously, with the mixing of the filler exhibiting the incorporation of flexibility in the polymer. So, the loading of the filler into poly (1,4-phenylene sulfide) can be optimized to enhance its thermoplastic properties for surface applications.

Radio-Absorbing Materials Based on Polymer Composites and Their Application to Solving the Problems of Electromagnetic Compatibility

Recently, designers of electronic equipment have paid special attention to the issue of electromagnetic compatibility (EMC) of devices with their own components and assemblies. This is due to the high sensitivity of semiconductor microcircuits to electromagnetic interference. This interference can be caused either by natural phenomena, such as lightning strikes, or by technical processes, such as transients in circuits during fast periodic or random switching. Either way, interference implies a sudden change in voltage or current in a circuit, which is undesirable, whether it propagates along a cable or is transmitted as an electromagnetic wave. The purpose of this article is to review the works devoted to the development, creation, and investigation of modern polymeric nanocomposite materials used for shielding electromagnetic radiation and their effective application for solving problems of electromagnetic compatibility. Additionally, the approach to design EMI shielding complex media with predetermined parameters based on investigation of various properties of possible components is shown. In the review, all polymer composites are classified according to the type of filler. The issues of the interaction of a polymer with conductive fillers, the influence of the concentration of fillers and their location inside the matrix, and the structure of the nanocomposite on the mechanisms of electromagnetic interaction are considered. Particular attention is paid to a new generation of nanocomposite materials with widely adjustable electrical and magnetic properties. A wide class of modern filled polymeric materials with dielectric and magneto-dielectric losses is considered. These materials make it possible to create effective absorbers of electromagnetic waves that provide a low level of reflection coefficient in the microwave range. The model mechanisms for shielding electromagnetic radiation are considered in the paper. A detailed review of the electro-physical properties of polymer nanocomposites is provided. Multilayer electrodynamic media containing combinations of layers of filled polymer composite materials with nanoparticles of different compositions and manufactured using a single technology will make it possible to create electrodynamic media and coatings with the required electro-physical characteristics of absorption, transmission, and reflection. Within the framework of the two-layer coating model, the difference in the effects of the interaction of electromagnetic radiation with conductive layers located on a dielectric and metal substrate is demonstrated. It is shown that in order to achieve optimal (maximum) values of reflection and absorption of electromagnetic radiation in the appropriate frequency range, it is necessary to fit the appropriate layer thicknesses, specific conductivity, and permittivity. Such approach allows designers to create new shielding materials that can effectively vary the shielding, absorbing, and matching characteristics of coatings over a wide frequency band. In general, it can be said that the development of innovative polymer composite materials for shielding electronic devices from electromagnetic interference and excessive electromagnetic background is still an important task. Its solution will ensure the safe and uninterrupted operation of modern digital electronics and can be used for other applications.