Preparation of Polypropylene-Organoclay Nanocomposites: Effect on Thermal,Morphological and Viscoelastic Properties

摘要

In the present work, PP-clay nanocomposites were prepared and the effect of nanoclay content on the properties of the nanocomposite was studied, polypropylene/surface modified clay nanocomposites were prepared via melt blending method in a laboratory mixing extruder (LME) using commercial polypropylene (PP) and nanoclay masterbatch in concentrations ranging from 5 to 15 wt%. The structure and thermal-mechanical features of the nanocomposites were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) as well as dynamic mechanical analyzer (DMA). For all nanoclays loadings, SEM shows homogeneous dispersion of the nanoclay in the polymer matrix. The DSC curves show a 15% increase in heat of fusion (crystallinity content) up to 5% wt nanoclay loading but then decreased at higher loadings. This is attributed to the nucleating role of the silica particles at low nanocaly content; however, at relatively high loadings, the presence of excessive number of silica particles hinders the motion of polymer chain segments and thus, retards crystal growth. The temperature sweep reveals an increase in storage modulus (G') with increasing nanoparticles content due to the restricted motion of the PP chains as a result of the interaction between the nanoclay and the matrix that depends on the interfacial area shared between the PP and the nanoclay. As the interfacial area increased, the interaction increased, and hence the chains were more restricted. Besides, the estimation of the softening temperature as well as the slope of the flat region of the curves show that the addition of the nonmaterial increases the thermal stability of the nanocomposites as compared to the neat polypropylene.