a .5 mm long, 50 nm in-diameter CNT). CNTs bundled into ropes are extremely
difficult to separate, and can slide past each other with very little effort. Such
mobility has cast some doubt on the use of randomly-dispersed CNTs as effective
reinforcement in nanocomposites, and is one of the reasons given as to why
nanocomposites have not yet achieved the theoretical predictions for their potential
[24].
Despite these difficulties, many have attempted to use CNTs to reinforce both
stiff and compliant matrices. While there exist some reports on the topic of their
use in reinforcing metals [25] and metal-oxides [26], the vast majority of work using
CNTs as mechanical reinforcement in composite materials has been by the way of
polymer matrices. The first report of CNTs in a polymer matrix was in 1994, where
Ajayan et al. showed that the cutting of an epoxy∕CNT composite could result in the
alignment of the CNTs embedded in the matrix [27]. Four years later, Wagner and
co-workers reported the first mechanical properties of a CNT∕polymer composite
by spreading a urethane∕diacrylate oligomer on a dried film of MWNTs prior to UV-
curing [28]. It wasn’t until the following year when Jia et al. attempted to create a
bulk composite by dispersing as-grown CNTs in a poly (methyl methacrylate) matrix
through mixing [29]. Despite sufficient stirring, they reported large clusters of CNTs
due in part to the reasons described previously regarding agglomeration.
Compounding the problems due to agglomeration, even dispersion in a
matrix is also somewhat hindered by the viscosity of the medium. Methods such as
ball mixing and extrusion have been reported as means by which to more-evenly