Biochar Reinforcement in Epoxy Composites for Enhanced Mechanical Properties and Fire Resistance

Abstract

In response to the growing need for environmentally sustainable and high-performance composite materials, this study explores the use of bamboo-derived biochar as a reinforcing filler in epoxy resin composites. Bamboo was selected due to its rapid renewability, abundant availability, and high lignocellulosic content, making it a viable precursor for biochar production through pyrolysis. Biochar was synthesized via slow pyrolysis at 500°C and integrated into epoxy resin at varying weight percentages (1%, 3%, and 5%) to evaluate its impact on mechanical, thermal, and fire-retardant properties. The fabricated composites were subjected to tensile testing, where the 5 wt% biochar-reinforced composite exhibited the highest performance, achieving an ultimate tensile strength (UTS) of 47.90 MPa, compared to 28.00 MPa in the neat epoxy. Young’s modulus increased from 1.85 GPa (0% biochar) to 2.42 GPa (5% biochar), indicating a significant enhancement in stiffness. Elongation at break showed a marginal decrease with increasing filler content, highlighting the typical trade-off between strength and ductility. Thermogravimetric Analysis (TGA) demonstrated improved thermal stability in composites containing biochar. The 5 wt% biochar sample showed a higher decomposition onset temperature and a residual mass of 38% at 800°C, compared to only 0.6% in the control sample. This indicates strong thermal barrier effects due to char formation. Although direct cone calorimetry testing could not be performed, a detailed review of similar studies and comparative interpretation with TGA data suggested improved flame retardancy with increased biochar content. Key inferred outcomes included longer time to ignition, reduced peak heat release rate (PHRR), and higher char residue, particularly in the 5 wt% composite. This investigation validates the multifunctional role of bamboo biochar in enhancing tensile strength, thermal stability, and flame-retardant behavior of epoxy composites. The findings support the use of such bio-based reinforcements in marine structural components, interior panels, and thermally sensitive applications. Moreover, this work opens future directions in optimizing pyrolysis conditions, scaling fabrication processes, and validating long-term durability and fire performance in real-world environments.