PP/clay nanocomposites: Effect of clay treatment on morphology and dynamicmechanical properties

The morphology and properties of polypropylene (PP)/clay nanocomposites are described. The melt intercalation of organophilic clay was carried out wit h a single-screw extruder. The effects of two kinds of treatments of clay a re discussed. Maleic anhydride (MAH)-grafted PP was used as a compatibilize r. The expansion of the intergallery distance of the clay was governed by t he interaction between the clay treatment and the compatibilizer. In one ca se, the composites exhibited significantly reduced intensities of diffracti on peaks, suggesting partial exfoliation of the clay layers, whereas for th e second clay sample, expansion of the gallery height was noted. The mechan ical properties of the PP/clay composites showed significant enhancement in their mechanical and thermal properties. About a 35% increase in the tensi le modulus and about a 10% increase in the tensile strength were observed. The thermal degradation temperature increased from 270 to about 400 degrees C as a result of the incorporation of clay, and the extent depended on the dispersion of clay in the composite. The most interesting outcome of this s tudy was the changes in morphology for PP/clay composites, which are report ed here for the first time. An optical microscopic study revealed that the PP/clay composites could be crystallized at higher temperatures than pure P P and that the morphology was remarkably altered because of the presence of layers of clay. (C) 2001 John Wiley & Sons, Inc.