Effect of temperature on EMI shielding behavior of jack fruit rags biochar and waste silk fiber-reinforced vinyl ester composite

Abstract

This study investigates the EMI shielding performance, mechanical, and dielectric properties of composite materials reinforced with waste silk fibers and biochar extracted from jackfruit rags, utilizing temperature aging techniques. Vinyl ester resin, selected for its reliability and water-resistant properties, served as the matrix material, while biochar from jackfruit rags and silk mats provided reinforcement. The biochar was effectively produced through a pyrolysis process at 750 °C, and the composite fabrication was achieved using a hand layup method followed by curing and post-curing processes. Among the tested specimens, VSB2, which contains 3-vol.% biochar, demonstrated superior mechanical properties, including a tensile strength of 131 MPa and a flexural strength of 152 MPa, significantly outperforming the base specimen V. The specimen also exhibited enhanced dielectric properties, with post-aging dielectric values of 5.8, 4.7, 3.7, and 2.6 at 8 GHz, 12 GHz, 16 GHz, and 18 GHz, respectively, indicating strong interaction between the biochar and the vinyl ester matrix. VSB2 also showed the highest EMI shielding effectiveness, with total shielding values of 31.5, 47.25, 63, and 68.25 dB at the respective frequencies, reflecting optimal absorption and reflection due to the well-dispersed biochar. The SEM analysis provided crucial insights into the microstructural enhancements responsible for these improvements. The uniform dispersion of biochar nanoparticles, and the improved interfacial bonding between fibers and the matrix, significantly contributed to the mechanical strength and durability of VSB2. Additionally, the study highlighted the positive impact of aging at 50 °C for 120 days, which further improved the dielectric and EMI shielding properties, confirming the composite’s stability and suitability for applications in high-temperature environments.