Rheological and electrical percolation thresholds of multi-walled carbon nanotube/in-situ polymerised Nylon12 nanocomposites

In this work, in-situ polymerisation of laurolactam in the presence of multi-walled carbon nanotube (MWCNT) was performed toward MWCNT/Nylon12 nanocomposite. Different levels of MWCNT (0.1, 0.3, 0.7, 1.2 and 3.5 wt%) were introduced to the monomer in the presence of 2 wt% toluene diisocyanate and 1 wt% sodium caprolactam as an activator and catalyst, respectively. The test results indicated that by increasing the amount of MWCNT, the conductivity of the nanocomposite increased up to that level at which it could serve as an electrically conductive material at room temperature. The melt rheological measurements showed a transition from liquid-like to solid-like state. The rheological results obtained within the linear viscoelastic region demonstrated that the rheological percolation threshold happened at 0.1 wt% multi-walled nanotube (MWNT), whereas the electrical percolation threshold appeared at 1.2 wt% MWCNT. A homogeneous dispersion of MWCNT into the Nylon12 matrix with a high aspect ratio of MWNT was achieved at a low percolation threshold. This mainly could be attributed to the fact that a denser MWCNT network was required for electrical conductivity, while a less dense MWCNT network sufficiently impeded Nylon12 chain mobility related to the rheological percolation threshold.