Development and Characterization of Sustainable Epoxy Biocomposites Reinforced with Coconut Shell Powder and GNP

The development of sustainable polymer composites reinforced with renewable resources and advanced nanomaterials has attracted considerable attention for multifunctional engineering applications. In this study, an environmentally friendly epoxy-based biocomposite (EBC) reinforced with coconut shell powder (CSP) and graphene nanopowder (GNP) was successfully produced through a casting process. CSP was employed as a bio-based filler, while GNP was incorporated at concentrations ranging from 0 to 0.75 wt.% to improve the overall performance of the composites. The effects of GNP loading on bulk density, tensile strength, elongation at break, Shore D hardness, thermal conductivity, dielectric properties, thermal stability, mechanical and microstructural characteristics were systematically investigated. The results demonstrated that the incorporation of GNP significantly enhanced the multifunctional properties of the improved EBCs. Bulk density increased from 1137.5 to 1143.1 kg m−3 with increasing GNP content. The optimum tensile strength of 28.6 MPa and Shore D hardness of 77.4 were achieved at 0.45 wt.% GNP, indicating effective stress transfer and strong interfacial interactions between the epoxy matrix, CSP, and GNP. Thermal conductivity increased from 0.110 to 0.149 W m−1 K−1, while the dielectric constant increased from 3.06 to 4.25 with increasing GNP concentration. Thermogravimetric analysis revealed improved thermal stability and enhanced char formation in graphene-containing composites. FTIR analysis confirmed that graphene acted primarily as a physical reinforcement without altering the fundamental chemical structure of the epoxy network. SEM and EDX investigations demonstrated improved structural compactness, homogeneous filler dispersion, and successful graphene incorporation. The findings indicate that GNP and CSP reinforced EBCs possess significant potential for lightweight structural materials, thermal management systems, dielectric components, and sustainable multifunctional engineering applications.