Preparation and characterization of microcellular polystyrene/polystyrene ionomer blends with supercritical carbon dioxide

Abstract

The preparation of microcellular polystyrene (PS), lightly sulfonated polystyrene (SPS), zinc-neutralized lightly sulfonated polystyrene (ZnSPS), and blends of PS/SPS and PS/ZnSPS via supercritical CO2 was carried out with the pressure-quench process. Both higher foaming temperature and lower pressure result in larger cell sizes, lower cell densities, and lower relative density for microcellular ionomers and blends as for microcellular PS. The difference among various microcellular samples is the change of cell size with the sample composition. The cell size decreases in the sequence from SPS, through PS/SPS blends, PS and PS/ZnSPS blends, to ZnSPS. The diffusivity of CO2 in samples also decreases in the sequence from SPS, through PS/SPS blends, PS and PS/ZnSPS blends, to ZnSPS. For this series of samples with similar structure and identical solubility of CO2, the varying diffusivity is responsible for the difference of cell sizes.