Role of Interfacial Adhesion Between Nutmeg Fiber and Biochar in Enhancing Electromagnetic Interference Shielding Efficiency of Biocomposites Under High-Frequency Bands

Abstract

To achieve superior mechanical strength and electromagnetic interference (EMI) shielding, this study develops lightweight vinyl ester biocomposites reinforced with nutmeg short fibers and porous watermelon rind biochar. The nutmeg fibers act as primary load-bearing reinforcements, while the carbon-rich biochar obtained through controlled pyrolysis functions as a lightweight functional filler that enhances dielectric polarization and electromagnetic attenuation. Among the developed formulations, the hybrid composition containing a higher fiber fraction with a moderate biochar loading exhibited the most balanced performance, demonstrating consistently improved dielectric behavior across a broad frequency range and effective EMI shielding within the practical attenuation range required for commercial applications. Mechanical evaluation revealed a clear improvement in tensile, flexural, impact, and surface hardness properties compared to non-hybrid or lower-filler systems, indicating efficient stress transfer and structural integrity. Scanning electron microscopy (SEM) confirmed bonding and homogeneous biochar dispersion, which collectively minimized microstructural defects and contributed to the observed property enhancements. Overall, the synergistic interaction between lignocellulosic fibers and conductive carbonaceous biochar highlights a sustainable and lightweight alternative to conventional synthetic or metal-based shielding materials, with strong potential for use in electronic enclosures, automotive interior components, aerospace cabin panels, and building-integrated EMI shielding applications where structural reliability and moderate electromagnetic attenuation are simultaneously required.