Sustainable Activated Carbon/Poly(vinyl acetate) Composites with Recycled Fillers for Enhanced EMI Shielding Applications

Electromagnetic interference (EMI) poses increasing challenges for compact electronic systems and emerging 5G/6G technologies, driving demand for Electromagnetic (EM) absorbers that are lightweight, low-cost, and environmentally sustainable. Conventional absorbers rely on ferrites, magnetic nanomaterials, and multi-step chemical synthesis, all of which consume energy and raw materials, involve hazardous reagents, and generate waste streams of their own. This study shows that two abundant waste streams, recycled tire particles (TP) and crushed glass (CG), can be converted into effective microwave-absorbing composites when combined with activated carbon (AC) in a poly(vinyl acetate) (PVAc) matrix through simple mechanical processing. The microstructure of the composites was examined via scanning electron microscopy (SEM), revealing systematic changes in surface texture, filler dispersion within the polymer matrix, and pore structure with increasing filler content. The complex permittivity, AC conductivity (σ), and loss tangent (tan δ) of the composites were determined from 0.2 to 20 GHz using an open-ended coaxial probe and correlated with their morphology. Dielectric loss was highest where the filler formed a continuous conductive network and decreased once an open pore structure developed, diluting the effective permittivity. Absorption-dominated EMI shielding was evaluated for metal-backed single layers using transmission-line (TL) theory, validated by full-wave simulations in Ansys HFSS. Pure AC composite absorbed weakly at the λ/4 condition but reached −13.5 dB at the 3λ/4 resonance. Incorporating waste-derived fillers improved its microwave absorption performance. At a thickness of 6 mm, the AC–TP composite (ACTP3) achieved a minimum reflection loss of −39.07 dB at 15.75 GHz, while the AC–CG composite (ACCG1) reached −29.4 dB at 16.75 GHz. These results demonstrate that strong absorption-dominated EMI shielding can be achieved using waste-derived carbon/polymer composites fabricated through simple mechanical processing. The approach offers a scalable and sustainable route to EMI shielding materials that avoids magnetic metals, nanomaterials, and chemical synthesis, while diverting industrial and post-consumer waste from landfill.