Characterization of dragon fruit biocarbon and Moringa oleifera pod husk microfiber toughened PVA composite thin sheet: Load bearing,dielectric and EMI shielding properties

Abstract

This study explores the electromagnetic interference (EMI) shielding efficiency and mechanical performance of polyvinyl alcohol (PVA) composite materials reinforced with Moringa oleifera pod husk microfibre and dragon fruit biocarbon. The combination of natural fiber and filler enhances the structural integrity and conductivity of the composite, making it a sustainable alternative to conventional EMI shielding materials. The PVA, a biodegradable polymer with a high crystalline nature, is used as the matrix material. Dragon fruit peel-derived biocarbon, prepared via pyrolysis at temperatures up to 800°C, serves as a carbon-rich filler, while Moringa oleifera husk microfibres are extracted through a retting and drying process. Composite films were produced using a solvent casting method, ensuring uniform dispersion of the fillers.Specimen PM4, comprising 30 vol.% Moringa oleifera microfibre and 4 vol.% dragon fruit biocarbon, exhibited superior dielectric properties with a dielectric constant of 5.3 at 8 GHz and 1.9 at 20 GHz, and a dielectric loss of 0.84 at 8 GHz and 1.89 at 20 GHz. These enhancements are due to the high dielectric nature of biocarbon and effective interfacial polarization. PM4 also demonstrated the best EMI shielding effectiveness, with total shielding values ranging from 15.75 dB at 8 GHz to 52.5 dB at 20 GHz, attributed to conductive pathways and increased surface conductivity that enhance absorption and reflection of electromagnetic waves. Conversely, specimen PM2, with 1 vol.% biocarbon, showed the highest mechanical properties, achieving a tensile strength of 63 MPa, elongation at break of 85%, and a hardness of 74 Shore-D. These values indicate optimal load transfer, reduced voids, and enhanced bonding within the composite. Scanning Electron Microscopy (SEM) analysis further supports these findings, revealing good adhesion between fibers and fillers and uniform dispersion of particles, which contribute to the overall performance, while also showing agglomerations that could impact properties if not controlled. This study concludes that optimizing filler content is key to achieving a balance between dielectric, EMI, and mechanical properties in PVA-based composites.