Supercritical CO2 processed polystyrene nanocomposite foams

Polystyerene (PS) nanocomposite foams were prepared using CO2 supercritical fluid (SCF) as a solvent and blowing agent. PS was first in situ polymerized with 0, 1, and 3% Montmorillonite-Layered Silicate (MLS) mixtures, which were then compression-molded into thin laminates. The laminates were foamed in a batch process at temperatures and pressures within the range of 60-85degreesC and 7.6-12 MPa. Characterization was accomplished with scanning electron microscopy (SEM), Differential Scanning Calorimetry (DSC), and X-ray Diffraction (XRD). SEM images revealed the effects of different processing parameters on the foam's cellular morphology, and also showed that the MLS layers were arranged in alignment with the foam cell walls. DSC data indicated that different concentrations of MLS have a notable effect on the glass transition temperature (T-g) of the composite, and that the foaming process itself alters the endothermic behavior of the material. XRD spectra suggested that the PS-MLS composite had an intercalated structure at both the 1 and 3% mixtures, and that the intercalation may be enhanced by the foaming process.