Authors: J.M. Torkelson, P.J. Brunner, N. Kane
Affilation: Northwestern University, United States
Pages: 556 - 559
Keywords: carbon nanotubes, as-received graphite, polypropylene, mechanical properties, exfoliation, dispersion
Polymer nanocomposites, particularly with carbon-based nanofiller, hold promise for large-scale, commercial application of novel materials with enhanced, tunable properties. Unfortunately, a stumbling block in achieving this goal on a commercial scale is the remarkable difficulty associated with dispersing nanofiller in polymer via conventional polymer processing methods. We have successfully addressed this challenge by preparing nanocomposites with low nanofiller levels, including as-received graphite (ARG) and carbon nanotubes, via a continuous, industrially scalable process called solid-state shear pulverization (SSSP). X-ray diffraction shows that SSSP leads to an almost complete disappearance of the scattering peak associated with the interlayer spacing in the unexfoliated ARG, indicating that high exfoliation is achieved in the graphene sheets making up ARG. Similarly, excellent dispersion has been achieved with SSSP followed by melt mixing of PP-carbon nanotube nanocomposites leading to individual nanotubes dispersed in PP. This excellent exfoliation and dispersion is accompanied by major property enhancements. For example, a 97.5/2.5 wt% PP/ARG nanocomposite made by SSSP exhibits a 100% increase in tensile modulus and a 50-60% increase in tensile strength relative to neat PP while retaining most of the net PP elongation at break. Similar mechanical property enhancements are achieved with 99/1 wt% PP/carbon nanotube nanocomposites.