Background: Carbon nanotubes (CNTs) are attractive nanostructures in this regard, primarily
due to their high aspect ratio coupled with high thermal and electrical conductivities. Consequently,
CNT polymer composites have been extensively investigated for various applications, owing to their
light weight and processibility. However, there have been several issues affecting the utilization of
CNTs, such as aggregation (bundling) which leads to a non-uniform dispersion and poor interfacial
bonding of the CNTs with the polymer, resulting in variation in composite performance, along with the
additional issue of high cost of CNTs.
Description: In this article, recent research and patents for polymer composites containing carbon nanomaterial
are presented and summarized. In addition, a rationale for optimally designed carbon nanotube
polymer composites and their applications are suggested. Above the electrical percolation threshold, a
transition from insulator to conductor occurs. The percolation threshold values of CNT composite are dependent
on filler shape, intrinsic properties of filler, type of polymer, CNT dispersion condition and so on.
Different values of percolation threshold CNT polymer composites have been summarized. The difference
in percolation threshold and conductivity of CNT composites could be explained by the degree of effective
interactions between nanotubes and polymer matrix. The reaction between surface functional
groups of CNTs and polymer could contribute to better dispersion of CNTs in polymer matrix. Consequently,
it increased the number of electrical networks of CNTs in polymer, resulting in an enhancement
of composite conductivity. In addition, to exfoliate nanotubes from heavy bundles, ultrasonication with
proper solvent and three roll milling processes were used. Potential reactions of covalent bonding between
functionalized CNTs and polymer were suggested based on the above rationale.
Conclusion: Through the use of CNT functionalization, high aspect ratio CNTs, and proper fabrication,
uniform dispersion of nanotubes in polymer can be achieved leading to considerable improvement
in electrical conductivity and electromagnetic interference (EMI) shielding properties.