A comparative study of the effect of multidimensional carbon fillers on polystyrene using supercritical carbon dioxide foaming

Due to its low thermal conductivity on average (~0.039 W/(m·K)), supercritical expanded polystyrene (PS) foam could be used as an insulation material in buildings to save energy and minimize the maintenance costs. However, the specific solubilizing and fast diffusing behavior of CO₂ in PS limited the formation of micropores and the further increase of macropores, which resulted in on limited decrease in thermal conductivity. In this study, one-dimensional carbon nanotubes, two-dimensional graphene, and three-dimensional activated carbon were loaded on PS using supercritical CO₂ foaming. The results demonstrated that all these three carbon nanomaterials doped on PS could generate more micropores and macropores during foaming. Moreover, the composite PS foams presented much lower specific thermal conductivity (0.360 cm³·W/(g·m·K)), higher cell density (up to 3.23 × 10¹⁴ cell/cm³), and compressive modulus (up to 1.66 MPa), overwhelming those of pure PS. Particularly, the continuous infrared thermography measurements found that two-dimensional graphene thermally outperformed the others, meaning comparatively better heat insulation effect after foaming. Therefore, multidimensional carbon nanomaterials were promising to minimize the negative environmental impact of PS foaming while comprehensively reinforcing it.