In a recent study published in J Mater Sci: Mater Electron, K. Kanchana, K. J. Anoop, V. P. Vinod, K. K. Kavitha, and Mathur Nadarajan Kathiravan have developed a novel lightweight biocomposite for electromagnetic interference (EMI) shielding. The increasing emission of electromagnetic and radio waves from electronic devices necessitates effective shielding solutions to protect the environment and improve device efficiency. This research uniquely utilizes waste biomass—specifically watermelon rinds for biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More and nutmeg husks for natural fibers—to create a sustainable and high-performance material.

The study focused on enhancing the mechanical, dielectric, and EMI shielding effectiveness of a vinyl ester polymer composite reinforced with surface-modified nutmeg shell fiber and porous watermelon rind biochar. The best mechanical performance was observed in composite VNB2, which contained 2.0 vol.% biochar and 30 vol.% silane-treated nutmeg shell fiber. This composition yielded a tensile strength of 154 MPa (175% increase over plain vinyl ester), a tensile modulus of 5.6 GPa (229.4% increase), a flexural strength of 221 MPa (151.1% increase), and a flexural modulus of 6.1 GPa (177.3% increase). For impact strength and hardness, composite VNB3, with 4.0 vol.% biochar and 30 vol.% silane-treated nutmeg shell fiber, showed superior properties: an impact strength of 5.8 J (383.3% increase) and a hardness of 90 Shore-D (9.8% increase), indicating excellent toughness.

Beyond mechanical strength, the biocomposite also exhibited impressive dielectric and EMI shielding capabilities. Composite VNB3, with its higher biochar content, demonstrated the best dielectric constant values, reaching 6.62 at E, 5.57 at F, 4.41 at I, and 3.89 at J (representing increases of 97.02%, 104.02%, 99.54%, and 131.54% respectively). This improvement is attributed to the formation of conductive networks and enhanced interfacial polarization within the material. Most notably, VNB3 achieved the highest EMI shielding effectiveness, reaching 8.82 dB at E, 14.28 dB at F, 20.16 dB at I, and 29.82 dB at J. This significant increase in shielding effectiveness is due to enhanced charge transport and multiple reflections facilitated by the increased biochar content, optimizing wave attenuation. These features make the biocomposite suitable for various electrical and electronic equipment in industries such as aerospace, communication, medical, and automotive.

Source: Kanchana, K., Anoop, K. J., Vinod, V. P., Kavitha, K. K., & Kathiravan, M. N. (2025). Electromagnetic shielding effectiveness of surface modified porous watermelon rinds biochar nutmeg short fibre reinforced lightweight vinyl ester biocomposite. J Mater Sci: Mater Electron, 36(830).