Nylon - Exfoliated Graphite Nanoplatelet (xGnP) Nanocomposites with Enhanced Mechanical, Electrical and Thermal Properties

摘要

Since the late 1990's, research has been underway in our group at Michigan State University to investigate the fabrication of new nano-size carbon material, exfoliate graphite nanoplatelets [xGnP]. The xGnP is fabricated from natural graphite and can be used as a nanoreinforcement for polymers as an alternative to expensive carbon-based nanomaterials. The thickness of the xGnP became around 5-10nm. The diameter can be controlled from sub-micron level to few hundred um, indication the aspect ratio can be controlled. The surface area of the material reached more than 100m~2/g. Since graphite is the stiffest material found in nature (Young's Modulus = 1060 MPa), having a modulus several times that of clay, accompanied with excellent strength, electrical and thermal conductivity, the xGnP should have similar properties to carbon-based nanomaterials, including carbon nanotubes, nanofibers, and fullerenes, yet the estimated cost is fur less than these materials. The cost of the graphite nanoplatelets was estimated to be S5/lb or less, which makes the material highly cost effective. Several papers related to this topic have been published since 1990's. In this research, the xGnP was used as nanoreinforcements for nylon 6 and Nylon 66 composites. The xGnP could improve the modulus of nylons better than other commercially available reinforcements. Impedance measurements have shown that the aspect ratio of the xGnP affect the percolation threshold of the composites. By using xGnP with high aspect ratio, the percolation threshold reached below 5vol%. Thermal conductivity measurement revealed that it reached almost 4 W/m~*K for xGnP/nylon nanocomposite. Gas permeation test showed that the barrier property was significantly improved with xGnP, almost as good as nanoclays.