Dynamic Mechanical, Rheological, and Thermal Properties of Intercalated Polystyrene/Organomontmorillonite Nanocomposites: Effect of Clay Modification on the Mechanical and Morphological Behaviors

摘要

Polystyrene (PS)/organomontmorillonite nanocomposites were prepared by melt processing with a twin-screw extruder. Sodium montmorillonite was organically modified with stearyl trimethyl ammonium chloride to evaluate the effect of clay modification on the performance of the nanocomposites. A comparative account of nanocomposites prepared with the commercial clay Cloisite 20A (C20A) is presented. X-ray diffraction studies indicated that the clay layers were completely dispersed, and a delaminated structure was formed in the case of C20A/PS and organomontmorillonite/PS nanocomposites. The dispersion characteristics of the clays within the matrix polymer were further investigated through transmission electron microscopy analysis. Mechanical tests revealed increases in the tensile, flexural, and impact strengths of 83, 55, and 74%, respectively, for C20A/PS nanocomposites at a 5% clay loading. The viscoelastic response of the nanocomposites, studied with dynamic mechanical analysis, also showed a substantial increase in the storage modulus of the nanocomposites with the incorporation of organically modified nanoclays. Furthermore, the melt-state rheology of the organically modified nanocomposites displayed three distinct regions—glassy, plateau, and terminal—from the high-frequency region to the lowfrequency region, with a considerable increase in the storage modulus in the glassy and terminal regions. Differential scanning calorimetry and thermogravimetric analysis were also used to evaluate the effect of the addition of nanoclays on the glass-transition temperature and thermal stability of the PS matrix.