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including water, DMSO, and NMP. This work shows that solvent choice can have a
dramatic effect on the mechanical properties of CNTs-polymer composites [90]. Also,
a critical CNTs concentration has defi ned as optimum improvement of mechanical
properties of nanotube composites where a fi ne network of fi ller formed [91]. There
are other effective parameters in mechanical properties of nanotube composite such
as size, crystallinity, crystalline orientation, purity, entanglement, and straightness.
Generally, the ideal CNT properties depend on matrix and application [92].The vari-
ous functional groups on CNT surface enable to couple with polymer matrix. Strong
interfacial interaction creates effi cient stress transfer. As previously pointed out, stress
transfer is a critical parameter to control the mechanical properties of composite. How-
ever, covalent treatment of CNT reduce electrical [93], and thermal [94, 95] properties
of CNTs. These reductions affect on ultimate properties of CNTs.
Polymeric matrix may wrap around CNT surface by non-covalent functionaliza-
tion. This process causes improvement in composite properties through various specif-
ic interactions [96]. In this context, Gojny et al. [97] evaluated electrical and thermal
conductivity in CNTs/epoxy composites. Figures 7.4 and 7.5 show respectively elec-
trical and thermal conductivity in various fi ller content including carbon black (CB),
SWNT, DWNT, and functionalized MWNT. The experimental results represented that
the electrical and thermal conductivity in nanocomposites improve by non-covalent
functionalization of CNTs.
Figure 7.4.
Electrical conductivity of the nanocomposites as function of filler content in weight
percent.
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