(128e) Processing, Properties and Structure of Exfoliated Graphite Nanoplatelet-Polypropylene Nanocomposites

This research explores the potential of using exfoliated graphite nanoplatelets (graphene sheets ~10nm thickness, ~1um diameter), a new material developed in our lab, as reinforcement in polypropylene. The goal is: (i) to fabricate exfoliated graphite nanoplatelet (xGnP) polypropylene nanocomposites and determine their thermo-mechanical and electrical properties (ii) to compare xGnP-polypropylene nanocomposites to composites made using other carbon-based electrically conductive fillers and (iii) to elucidate the fundamental interfacial (i.e. adhesion and dispersion), processing and property mechanisms governing their use in polyolefin thermoplastics. xGnP-polypropylene(PP) nanocomposites will be fabricated in a two-step process; compounding and molding (injection or compression). Two approaches are employed for the compounding: (i) solution method and (ii) melt mixing, using a twin-screw extruder. The xGnP will be characterized using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM) to quantify the morphology and the fracture surface of the nanocomposites. Results include thermal (coefficient of thermal expansion and thermal conductivity), and mechanical properties (flexural strength, modulus of elasticity, storage modulus and impact strength). In addition, the electrical conductivity and the percolation threshold of the xGnP-polypropylene nanocomposites will be determined as a function of the xGnP's aspect ratio and the processing method used. Furthermore, xGnP, due to its layered structure, increases the barrier properties of the neat polymer as shown by permeability experiments. Finally, the effect of xGnP on the crystallinity of neat PP will be explored using Differential Scanning Calorimetry (DSC), XRD, and optical microscopy. The contribution of this research will be the elucidation of the structure-processing-property relationships of the xGnP-PP nanocomposites which are very important from an application point of view, as well as, the fundamental understanding of how these properties are related to the xGnP's microstructure; the sate of dispersion, the aspect ratio, orientation and the interactions between xGnP and the polymer chains.