Layered-silicate based polystyrene nanocomposite microcellular foam using supercritical carbon dioxide as blowing agent

Exfoliated layered-silicate in the polystyrene (PS) block copolymer with different molecular weights was employed as a model material to investigate the PS nanocomposite microcellular foams expanded by supercritical carbon dioxide. Using a well-controlled foaming procedure, we investigated the influence of molecular weight of PS, dispersion and loading of layered-silicate and pressure drop rate of a blowing agent on the cell size and cell density. Our experimental results indicate that only exfoliated layered-silicate can inhibit the cell expansion and has high nucleation efficiency during foaming. The average cell diameter can be reduced from 6 μm to 1.4 μm and the cell density can be increased from 7.6 × 10⁹ cells/cm³ to 5.0 × 10¹¹ cells/cm³. On the contrary, aggregated layered-silicate in PS did not show any effect on the cell morphology of PS foam.