Bimodal cell structure of a layered silicate-thermoplastic olefin elastomere nanocomposite

A new approach in terms of cell size control and thus achieving a unique bimodal cell structure of microcellular foamed polymer-layered silicate nanocomposite in batch processing is reported. With progressive passes through the extruder, the TPO samples were foamed at batch process using supercritical CO2 at two different temperatures-165 °C (10.6 MPa), just below the melting temperature of either layered silicate-thermoplastic olefin elastomer or maleic anhydride modified PP matrix without clay and 185 °C (11.2 MPa) in order to eliminate crystalline content of the sample. In order to prevent the cells coalescence and also with respect to the limited ability of cooling the high pressure vessel with cooling jacket, we proposed to control cell growth by pressure. When foamed, the higher SEM magnifications reveal interesting phenomenon inside the cells structure of neat TPO and TPO loaded with clay nanoparticles. The coalescence cells in different size exhibit open smaller cells inside the inner structure. Such a structure led to a substantially higher cell density than apparent density of 2.37x10⁶ cells/cm³.