Phosphonium modified organoclay as potential nanofiller for the development of exfoliated and optically transparent polycarbonate/clay nanocomposites: Preparation and characterizations

Here, we report the preparation and properties of optically transparent polycarbonate (PC)/clay nanocomposites through the conventional methods of nanocomposites preparation (melt blending and solution blending) leading mainly to the exfoliation of thermally stable phosphonium modified organoclay. The organic modification of the sodium montmorillonite (Na-MMT) was done by the inclusion of ethyl triphenylphosphonium (ETPP) ion inside the layer spacing of Na-MMT clay through ion exchange reaction. The resulting quaternary phosphonium modified organoclay showed outstanding stability against thermal degradation in isothermal TGA analysis at the processing temperature of PC (280 °C). Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) studies revealed that, the MMT layers were well exfoliated at lower loading (0.5 phr) of ETPP-MMT, whereas, presence of a mixed clay morphology of exfoliation with minor intercalation was obtained at higher loading (1 phr) of the clay in both the melt and solution blended PC/ETPP-MMT nanocomposites. The tensile strength and Young modulus were increased, whereas, elongation at break was decreased with increase in clay loading in both the melt and solution blended ETPP-MMT nanocomposites. The thermo-mechanical properties of the nanocomposites were superior to that of the neat PC in both the glassy and rubbery regions. The optical transparency of PC was retained without development of any colour in the PC/ETPP-MMT nanocomposites.