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The electromagnetic shielding effectiveness of kenaf fiber based composites with different iron oxide impregnation levels was investigated. The kenaf fibers were retted for removing the lignin and extractives from the fibers and magnetized. Using the unsaturated polyester and the magnetized fibers, kenaf fiber based composites were manufactured by the compression molding process. The transmission energies of the composites were characterized when the composite samples were exposed under the irradiation of electromagnetic (EM) wave with a variable frequency from 9 GHz to 11 GHz. Using the Scanning Electron Microscope (SEM), the iron oxide nanoparticles were observed on the surfaces and inside the micropore structures of single fibers. As the Fe content increased from 0% to 6.8%, 15.9% and 18.0%, the total surface free energy of kenaf fibers with the magnetizing treatments increased from 44.8 mJ/m 2 to 46.1 mJ/m 2 , 48.8 mJ/m 2 and 53.0 mJ/m 2 , respectively, while the modulus of elasticity reduced from 2875 MPa to 2729 MPa, 2487 MPa and 2007 MPa, respectively. Meanwhile, the shielding effectiveness was increased from 30–50% to 60–70%, 65–75% and 70–80%, respectively. [ABSTRACT FROM AUTHOR]

Using natural fiber mats, aluminum sheets and epoxy resin, hybrid composites were fabricated through vacuum assisted resin transfer molding (VARTM) process. With novel sandwich structures, these hybrid composites contain natural fiber-based shells and ultra-thin aluminum sheet core. The hybrid composites offered excellent electromagnetic interference (EMI) shielding performance with good mechanical properties inherited from aluminum sheets and natural fiber-based composites, respectively. Furthermore, the shell material (natural fiber-based composites) provides protection of the aluminum sheets from exposing to atmosphere directly to prevent being corroded. In this study, the EMI shielding effectiveness, microstructure, flexure property, tensile property, and internal bonding strength of the hybrid composites were examined. The excellent EMI shielding performance and good mechanical properties enable the new hybrid composites to be used as engineering materials in the EMI protection fields. [ABSTRACT FROM AUTHOR]

Natural fiber reinforced composites with dual-functional properties, including electromagnetic shielding and paramagnetic functions, as well as improved water-resistant property, were fabricated using vacuum assisted resin transfer molding (VARTM) process. Magnetite particles were firstly mixed with kenaf fibers to form a mat, followed by resin intrusion and compression for the composite fabrication. The obtained kenaf fiber/magnetite/polyester composites were endowed with electromagnetic shielding and paramagnetic properties, without compromising the mechanical properties. When 35.2% magnetite was incorporated into the composites, the electromagnetic interference shielding effectiveness reached 79.2% with the range 8–12 GHz, and the saturation magnetization was 29.2 emu g −1 . The 24-h thickness swelling and water absorption of the composites after introducing magnetite were drastically reduced from 19.7% to 2.4% and 18.3% to 2.6%, counting as the decreases of 87.6% and 73.4%, respectively. It was indicated that the water resistance of the composite was improved significantly. [ABSTRACT FROM AUTHOR]