Figure 2. High-resolution transmission electron micrographs of the
graphene-carbon nanotube hybrid material for the production of
fiber-reinforced polymer composites.
The effect of the weight fraction of the graphene-carbon nanotube hybrid
material on the modulus of elasticity is illustrated in Figure 3 for the
fiber-reinforced polymer composite. Intense research has been focused on
polymer nanocomposites because of their potential to dramatically
enhance properties relative to neat polymer and to yield multifunctional
materials [53, 54]. Carbon nanotubes have been extensively studied
as nanofillers because of their low density, high aspect ratio, and
excellent mechanical, electrical, and thermal properties [55, 56].
However, major challenges remain in the development of polymer-carbon
nanotube nanocomposites, especially as related to carbon nanotube
dispersion via industrially scalable, environmentally friendly methods
and understanding the relationship between dispersion and optimum
properties [57, 58]. Several strategies have been studied to achieve
well-dispersed polymer-carbon nanotube nanocomposites, including melt
mixing, polymer-carbon nanotube blending in solvent, and in situ
polymerization [59, 60]. Use of melt mixing alone often leads to
limited carbon nanotube dispersion in polymer. Blending polymer and in
situ polymerization methods can lead to better dispersion, but the
former is not environmentally friendly and both methods have limited
applicability and scalability. One or more mechanical or physical
properties of the graphene-carbon nanotube fiber-reinforced polymer
composite are enhanced, including but not limited to increased Young’s
modulus and increased yield strength, electrical conductivity, thermal
stability and crystallization rate, as compared to the corresponding
neat polymer. For example, the modulus of elasticity of the composite is
enhanced as compared to the corresponding neat polymer. The method of
preparing the composite comprises providing a polymer component and a
graphene-carbon nanotube mixture; applying a mechanical energy thereto
through solid-state shear pulverization in the presence of cooling at
least partially sufficient to maintain such a polymer component in a
solid state, such pulverization at least sufficient to provide a
pulverization product comprising a graphene-carbon nanotube component at
least partially homogeneously dispersed therein; and melt-mixing such a
pulverization product, to provide a graphene-carbon nanotube
fiber-reinforced polymer composite. Crystallization kinetic effect can
be selected from increased rate of isothermal crystallization and
decreased distribution of crystallization time. Solid-state shear
pulverization and melt-mixing can be at least partially sufficiently to
affect a mechanical and physical property of such a mixture, such a
property as can be selected from Young’s modulus, yield strength,
electrical conductivity, and thermal stability. Dispersion can be
characterized by field-emission scanning electron microscopy and the
absence of agglomeration at micron-length scales under microscopy
conditions.