Structure and mechanical properties of polycarbonate modified clay nanocomposites

Polycarbonate (PC)/modified clay nanocomposites were prepared, in the absence and presence of different amounts of maleic anhydride grafted polypropylene (PP-g-MA), by direct melt blending. Their structures, as well as mechanical, morphological and thermal properties, were characterized by X-ray diffractometry (XRD), tensile testing, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The XRD results of the PC/clay nanocomposites showed that they had intercalated structures, although some exfoliation was visible at low clay contents, that the gallery heights of the PC/clay nanocomposites were almost the same, and that some of the clay layers collapsed as a result of modifier decomposition at the high processing temperature. The XRD patterns of the PC/PP-g-MA/clay nanocomposites clearly show less intercalation and more exfoliation with increasing PP-g-MA content. These results were supported by TEM observations. Both the tensile strength and modulus show substantial improvements with both increasing clay and PP-g-MA contents, while the elongation at break substantially decreases, although the presence of PP-g-MA somewhat improves these values. All the nanocomposites have lower thermal stability than pure PC, but the presence of PP-g-MA seems to improve the thermal stability of these samples.