(604e) Polymer-Graphite Nanosheet Composites Via Solid-State Shear Pulverization: a Robust and Practical Approach to Effective Nanofiller Dispersion

In the growing field of polymer nanocomposites, carbon-based nanofillers such as carbon nanotubes and graphite nanosheets have a number of potential technological impacts because they can impart electrical conductivity in addition to providing enhanced mechanical, thermal and barrier properties in the resulting composites. Analogous to well-studied polymer-silicate clay systems [1], superior properties in polymer-graphite nanocomposites can be achieved upon complete exfoliation and good dispersion of the graphene sheets in the polymer matrix. There have only been a few reports on effective graphite nanosheet dispersion via in situ polymerization [2-3] and melt processing [4].

We herein propose solid-state shear pulverization (SSSP) as a novel processing method to disperse carbon-based nanofillers in polymer nanocomposites. In the past, SSSP has proven to successfully compatibilize polymer blends of unmatched viscosities [5] and exfoliate silicate layers in polymer-clay nanocomposites [6]. Unlike the conventional nanofiller dispersion techniques in the literature, SSSP can potentially disperse nanofillers more simply and effectively without chemical modification, use of solvents, or heat. SSSP subjects the system to repeated fragmentation and fusion steps in the solid state below the transition temperature of the polymer, and thus can form polymer nanocomposites without the limitations of thermodynamics, viscosity and degradation. Additionally, the continuous nature of SSSP makes the process amenable to industrial scale-up and subsequent product optimization

We investigated various polymer-graphite nanocomposites based on several commodity thermoplastics via SSSP. Electron microscopy and X-ray diffraction were employed to probe the characteristic spacing between graphite sheets in the nanoscale morphology. Mechanical properties were measured using tensile and dynamic mechanical tests, and the barrier properties were obtained from oxygen permeation testing. Differential scanning calorimetry and thermogravimetric analysis were employed for thermal characterization, and AC impedance measurement for electric characterization.

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