Sustainable biocarbon derived from walnut shells and its composites with mono-functional bio-benzoxazine for advanced applications

Abstract

Using agricultural waste as biocarbon material is a recent development with many potential applications. Nutshells can be utilized to produce biocarbon, enhancing the electrical properties of thermoset composites. In this research, Walnut shells (WSs) were carbonized at 750 °C, and activated carbon filler was thoroughly examined. Isothermal compression molding was used, and composites were produced by incorporating 1–2.5 wt.% of carbonized bio-filler (CW) into Vanillin-furfuryl amine-derived bio-benzoxazine. The composites showed improved thermal stability, increasing from 293 to 321 °C; Char yield enhanced from 53.3% to 60.4%. The flexural modulus and flexural strength exhibited enhancements of 41.3% and 20%, respectively, while toughness significantly increased from 0.87 to 0.94 N-mm compared to the neat matrix. Heat deflection temperature tests showed improved thermomechanical properties in composites. Flammability tests indicated that they are flame-resistant and fire-safe due to the CW filler. Thermal conductivity enhanced by 6%, and dielectric characteristics increased by 56.7% with 2.5 wt.% filler reinforcement. With the above findings, these composites can be utilized in designing parts exposed to fire, high temperatures, efficient energy storage, enhanced functionality in electronic devices, and improved insulation efficiency.