Development of Epoxy Composites With Biochars Derived From Chromium‐Containing Leather Waste

ABSTRACT This work presents a novel approach to valorizing chromium‐containing leather waste by converting it into biochar and incorporating it as a sustainable functional filler in epoxy composites cured with cardanol‐derived phenalkamine (CPKA). The resulting leather waste‐derived biochar (LWB)/epoxy composites exhibited significantly enhanced tensile modulus, thermal, and dielectric properties. Epoxy composites incorporating 20% LWB demonstrated substantial property enhancements, with the tensile modulus increasing from 328 ± 18 to 806 ± 14 MPa and thermal conductivity improving by 83% to 0.55 W/(m·K). Thermogravimetric analysis demonstrated enhanced thermal properties compared to neat epoxy, while dielectric measurements showed an increase in both the dielectric constant and dielectric loss with the addition of LWB. In addition, hexavalent chromium levels in the composites remained within the acceptable range for general plastic products, confirming their safety and suitability for broad industrial applications. These findings demonstrate a sustainable and effective strategy for converting hazardous leather waste into valuable biochar fillers for high‐performance epoxy composites, with promising applications in structural components, electronic encapsulation, and electromagnetic interference shielding.