TPO based nanocomposites. Part 1. Morphology and mechanical properties

The relationship between morphology and the mechanical properties of thermoplastic olefin (TPO) materials that are reinforced with organoclay fillers and prepared by melt processing is reported. Nanocomposites based on blends of polypropylene and elastomer and using an organoclay masterbatch were prepared in a twin-screw extruder. Transmission electron microscopy, atomic force microscopy and wide-angle X-ray scattering were employed to carry out a detailed particle analysis of the morphology of the dispersed clay and elastomer phases for these nanocomposites. The improvement in mechanical properties, e.g. stiffness enhancement as evaluated by stress-strain analysis and impact strength obtained from notched Izod impact tests, were successfully explained in terms of morphological changes induced by the presence of the clay and elastomer particles. Quantitative analyses of TEM micrographs and AFM images revealed a decrease in the aspect ratio of the clay particles and a reduction in the size of elastomer particles with increasing clay content. In addition, WAXD scans indicated a skin-core effect for the injection molded specimens in terms of both polypropylene crystal orientation and clay filler orientation. This information is essential for the understanding of the mechanism of mechanical property enhancement in nanocomposite materials.