Micromechanical modeling of the elastic behavior of polypropylene based organoclay nanocomposites under a wide range of temperatures and strain rates/frequencies

摘要

Montmorillonite clays are one of the most used nano-reinforcement in polypropylene nanocomposite systems, which can enhance the mechanical properties with a low volume fraction. In this study, the nanocomposites were obtained by using a melt mixing technique. Dynamic mechanical analysis (DMA) was realized to investigate the elastic behavior of pure polypropylene and polypropylene based organoclay nanocomposites. Previous results from high strain rate uniaxial compression tests (split Hopkinson pressure bar) are also used in this study. Two micromechanical models, based on two-phase and three-phase composite approaches, were incorporated into a statistical model to describe the dependence of the elastic modulus on the test temperature, frequency/strain rate, volume fraction of organoclay and on the extent of exfoliation. The predictions of the nanocomposite elastic modulus by both models showed a good agreement with experimental results. The estimated average particle thicknesses, from the proposed modeling, indicate a decrease of the exfoliation degree with the increase of fillers' volume fraction. This extent of exfoliation trend reflects well the results by the transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements conducted in a previous work.