Lightweight Polystyrene/Exfoliated Graphite‐Graphene Foam‐Based Composites Aimed for EMI Shielding Application

Lightweight polymer foams capable of mitigating electromagnetic interference (EMI) are sought for next‐generation electronics, transport, and construction, yet scalable routes based on commodity polymers remain limited. In this work, polystyrene (PS) foam‐based composites containing graphite or thermally expanded graphite exfoliated into few‐layer graphene nanosheets (EG therm.exp ) were fabricated on a semi‐industrial line using conventional CO 2 foaming and characterized by SEM, FTIR‐ATR, TGA/DSC, four‐probe conductivity, and EMI measurements. SEM revealed closed‐cell structures with broadened cell‐size distributions and preferential localization of EG therm.exp at PS bead interfaces, while TGA/DSC showed 10°C–20°C increases in degradation temperatures, indicating improved thermal stability due to the incorporation of graphene nanoparticles into the polymer walls of the foam. Electrical conductivity increased from 1.77 × 10 −5 S m −1 for neat PS to 3.19 × 10 −5 and 2.49 × 10 −5 S m −1 for PS/graphite and PS/EG therm.exp , respectively. These results demonstrate that carbon‐based fillers can simultaneously enhance the thermal stability, conductivity, and EMI response of PS foams, providing a scalable platform for further microstructural and compositional development toward higher‐performance EMI shields.