Polypropylene Nanocomposites: Effect of Organo-modified Layered Silicates on Mechanical, Thermal & Morphological Performance

Abstract

The present article reports the mechanical, thermal and morphological characteristics of polypropylene — maleic anhydride grafted polypropylene —organically modified MMT (PP-PP-g-MAH-OMMT) nanocomposites. PP nanocomposites were prepared by melt mixing in a twin screw extruder followed by injection moulding. Sodium montmorillonite has been organically modified using quaternary ammonium intercalants. A comparative account with commercial quaternary ammonium modified clay; Cloisite 15A has also been presented. Mechanical tests showed considerable improvement in tensile, flexural and impact properties of PP matrix with the incorporation of organically modified nanoclays. Furthermore, the quaternary ammonium intercalants exhibited improved performance with an optimum improvement in compatibilized PP/Cloisite 15A nanocomposites. The morphology of the nanocomposites has been examined using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Morphological findings revealed efficient dispersion of organically modified nanoclays within the PP matrix. PP-g-MAH compatibilized PP/Cloisite 15A nanocomposites displayed finely dispersed exfoliated nanomorphology as compared with other systems. The crystallization, melting behavior and thermal stability of the nanocomposites has been studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) which indicated an increase in crystallization temperature as well as thermal stability of PP matrix in Cloisite 15A nanocomposites. DMA curves also confirmed an increase in storage modulus of PP matrix in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of organically modified nanoclays.