Synergistic Effects of Carbon Additives and Supercritical <scp>CO<sub>2</sub></scp> on Cell Morphology and Thermal Insulation of Extruded Polystyrene Composite Foam
Apurv Gaidhani, Guoshan Min, William Z. Xu, Lauren Tribe, Paul A. Charpentier
Abstract
ABSTRACT Polystyrene (PS) foams with carbon additives are widely used in building applications due to their excellent thermal insulation properties, contributing to reduced energy consumption. However, the role of supercritical CO 2 (sc‐CO 2 ) as a blowing agent, in synergy with different forms of carbon additives, remains not fully understood in the context of PS extrusion foaming. In this study, composite foams were prepared by incorporating graphene nanoplatelets (GNP) and flaked graphite (FG) into PS using an extrusion foaming process. Results show that sc‐CO 2 pressure plays a critical role in enhancing carbon dispersion, thereby significantly influencing foam morphology. At high sc‐CO 2 pressure, the cell density of PS foam increased by up to two‐fold with a relatively low carbon loading (0.75 wt%). Moreover, the thermal conductivity of PS composite foam with 1.5 wt% FG was reduced by 6%, reaching a value of 32 mW/(m K). Transmission electron microscopy (TEM) confirmed a uniform dispersion of carbon particles in foams produced at elevated sc‐CO 2 pressures. This study proposes a viable processing strategy for developing carbon‐reinforced PS composite foams with enhanced thermal insulation for energy‐efficient building applications.