Scaling behavior of the elastic properties of non-dilute MWCNT-epoxy suspensions

In this paper, the network structure of multiwalled carbon nanotube (MWCNT)-epoxy suspensions was investigated under the influence of flow history and temperature using the scaling behavior of the linear viscoelastic properties of the concentrated suspensions above their gel point. It is shown that the suspensions have a self-similar fractal structure with the dimension of about 2.15, characteristic of weakly flocculating suspensions and their elasticity originates from inter- and intra-floc links of nanotubes. From the scaling behavior of the flow-induced storage modulus and the critical strain for the limit of linearity, it is shown that the fractal dimension and so the superstructure of the network did not change significantly under the influence of the flow history due to the initial compact structure of the network before pre-shearing. The time-temperature superposition principle was verified for the CNT suspensions and the shift factor was accounted for by an Arrhenius equation. The reduced storage and loss moduli of the suspensions using the complex modulus of the neat epoxy were shown to increase with temperature revealing more inter-particle interactions as the temperature was raised. However, it was impossible to conclude on the changes of the fractal dimensions with temperature.