Enhancing mechanical performance of polystyrene carbon composite foams through supercritical CO ₂ foaming: An experimental study

Conventional polystyrene (PS) foams are widely used in packaging and insulation, but suffer from limited mechanical strength, which restricts their use in load-bearing applications. This study investigates the enhancement of the mechanical performance of PS foam through the incorporation of graphene nanoplatelets (GNP) and flaked graphite (FG), processed via supercritical CO 2 (sc-CO 2 ) extrusion foaming at two pressures (17.3 MPa and 20.6 MPa). The influence of sc-CO 2 pressure on additive dispersion and mechanical behavior was evaluated using compression testing, dynamic mechanical analysis (DMA), micro-computed tomography (micro-CT). Results showed that increasing the sc-CO 2 pressure significantly enhanced compressive strength from 0.30 MPa to 0.40 MPa for 0.75 wt% GNP foams (34% increase) and from 0.30 MPa to 0.50 MPa for 0.75 wt% FG foams (66% increase). Enhanced storage and loss moduli in DMA confirmed improvements in stiffness and energy dissipation. Micro-CT imaging revealed more well-defined closed-cell structures and uniform carbon particle dispersion at the higher pressure. Overall, these findings emphasize the importance of pressure-optimized sc-CO 2 foaming as an effective strategy for producing lightweight, durable PS-carbon composite foams suitable for structural, insulation, and packaging applications.