Abstract

This research investigates the influence of copper-modified activated carbon (Cu-AC) on the structure, electrical properties, mechanical properties, thermal properties, and vulcanisation behaviour of natural rubber (NR) composite materials, aiming to clarify the role of copper in interfacial interactions and vulcanisation chemistry. Cu-AC containing 1% and 2% copper was introduced into NR at a fixed loading of 10 phr, and the resulting NR composites were analyzed using FTIR, XRD, SEM/EDX, mobile viscometer, TGA, DSC, and density functional theory (DFT) calculations. The incorporation of Cu-AC remarkably improved dielectric performance, with the dielectric permittivity increasing to ε' = 8.63 at 1 kHz for the 2% Cu-AC NR composite, compared with 3.92 for unmodified activated carbon and 1.72 for neat NR, while maintaining a low dielectric loss of 0.0006. Mechanical properties were also improved, as tensile strength increased from 5.97 MPa for neat NR to 12.34 MPa and 14.40 MPa for composites containing 1% and 2% Cu-AC, respectively. FTIR combined with DFT analysis indicates that copper participates in the curing process through CuS coordination and preferential adsorption of mercaptobenzothiazole (MBT) (E<inf>ads</inf> = −2.18 eV), thereby influencing crosslink density and curing behaviour. In summary, the results show that copper-modified biomass-derived activated carbon can improve both the dielectric response and mechanical performance of NR composite materials, supporting their potential for use as sustainable and flexible multi-purpose materials, consistent with the Bio-Circular-Green (BCG) model.