Sustainable EMI Shielding Composites from Recycled PE/PP and Coconut Shell–Derived Activated Carbon

Abstract

This work explores the use of coconut-shell-derived activated carbon (AC) to improve the properties of recycled polyethylene/polypropylene (PE/PP) composites. AC was added at 0-25 wt% using melt blending followed by compression moulding. As the AC content increased, the composite density rose from 0.8987 to 0.9627 g/cm³, while the melt flow index dropped from 58.29 to 17.47 g/10 min, reflecting reduced chain mobility and stronger interactions between the filler and polymer matrix. Mechanical properties also improved, with the tensile modulus and tensile strength reaching 1643 and 16.8 MPa, together with a noticeable increase in ductility. DSC analysis showed two melting transitions at around 128 and 163 °C, and both the crystallization temperature (122.24 °C) and crystallization enthalpy (574 J/g at 5 wt% AC) increased, confirming that AC acts as an effective nucleating agent. The EMI-shielding performance of the composites improved steadily with AC loading. The best attenuation was obtained at 25 wt% AC, where the transmitted signal reached –18.64 dBµV at 3.82 GHz. This enhancement is attributed to the development of semi-continuous conductive pathways and stronger dielectric loss mechanisms. Overall, the results show that incorporating bio-based AC into recycled PE/PP is a practical and sustainable way to produce lightweight, low-cost composites with improved mechanical performance and effective EMI-shielding capability for use in electronic and packaging applications.