High-frequency EMI shielding performance of vinyl ester composites reinforced with hennep fiber and nutmeg husk biochar

The present study aims to develop a light-weight electromagnetic interference (EMI) shielding using naturally extracted hennep fiber, and nutmeg waste derived highly porous biocarbon reinforced vinyl ester composite, which presents the novelty of the study. The biocarbon is derived by slow pyrolysis method and fabrication is done by hand layup technique. The prepared shielding composite performances are assessed in accordance with the American Society for Testing and Materials (ASTM) standard. The results showed that composite VN2 (30-vol.% hennep fiber and 2-vol.% biochar) had the best mechanical properties, with a hardness of 85 Shore D, a tensile strength of 147 MPa, a tensile modulus of 5.3 GPa, a flexural strength of 210 MPa, a flexural modulus of 5.8 GPa, and an Izod impact resistance of 5.3 J/m. These superior mechanical values are because of optimal fiber–matrix bonding and uniform dispersion of filler into the matrix, which provides excellent load-bearing capacity and stiffness and it could be better viewed in scanning electron microscopy (SEM) analysis. Moreover, the composite VN3 (30-vol.% hennep fiber and 4-vol.% biochar) showed maximum dielectric features of having dielectric constant of 6.8 at low frequencies (E band) and 4.0 at high frequencies (J band), and dielectric loss reaching 0.85. The electromagnetic interference shielding performance of the developed composites was evaluated over the E-, F-, and J band frequency ranges (2–18 GHz) to assess their high-frequency shielding effectiveness for advanced electronic and communication applications. VN3 also achieved the best EMI shielding effectiveness with values of 12, 35, 45, and 55 dB across frequencies E, F, I, and J, respectively. These maximum dielectric properties and improved shielding effectiveness are because of porous nature of biochar particles and their even dispersion in the composite creates effective shielding effectiveness and dense conductive networks, improving interfacial polarization. Due to their efficient shielding behavior and source from natural substance it could be utilized in areas such as satellite communication network, biomedical super computers, automotive and aviation sector, drone military industrial application, space jets, and wearable gadgets.