Specific rheological and electrical features of carbon nanotube dispersions in an epoxy matrix

Low viscosity processing using hybrid CNT-coated silica particles to form electrically conductive epoxy resin composites

“…The viscosity is then observed to decrease by up to two decades while the stress remained essentially constant, before flow initiates at apparent yield stresses of ≈40 Pa and ≈250 Pa for the 0.17 and 0.33 wt.% loadings, respectively. This behaviour is once again indicative of the break-up of the CNT network, and similar observations have been reported for aqueous [22] and other epoxy [21] CNT suspensions. In contrast, the grafted CNTs of the SG6_3 particles remain strongly attached to the substrate and are relatively short.…”

“…Similar modulus behaviour, which is typical of a strong gel [22], has been reported for other CNT suspension [21,22,27]. In the case of SG6_3 suspensions, G′′ always dominates G′ (Figure 6b) indicating that these suspensions exhibit only viscous behaviour even at a CNT loading of 1.65 wt.…”

“…In contrast, the two NC suspensions containing discrete, nongrafted CNT exhibit viscosities that are between 1 and 2 orders of magnitude higher at 10 -1 s -1 and which decrease sharply as the shear rate increases. Similar large increases in viscosity at low shear rates resulting from CNT addition have been observed for suspensions in other epoxy resins [18][19][20][21] and water [22], and are attributed to the formation of a percolated network between the CNTs. As the shear rate was increased to > 200 s -1 , the viscosities of the NC suspensions decrease and approach those of the epoxy and the SG6_3 suspensions; behaviour indicative of the break-up of the CNT network [18,20].…”

Evolution of carbon nanotube dispersion in preparation of epoxy-based composites: From a masterbatch to a nanocomposite

“…This, together with a loss modulus (G&) remaining lower than G" all over the swept frequency range, indicates the presence of a network of entangled CNT clusters with a pseudo-solid-like behaviour. This situation is quite comparable to the cases where a solid-like gel network is emerged following an increase in the nanofiller content as observed in [21,30]. In contrast, the diluted 'N' resin system represents the typical hallmarks of a liquid-like material with a perfectly linear G&(!)…”

“…Furthermore, the storage modulus (G") of the resin system 'A' (solid circles) develops a plateau at low frequencies (!'0). A frequency independent rubbery plateau of G" is caused by highly interacting nanotubes, and is a well-known characteristic of a network or a structured entanglement in the suspending medium [21,30,31]. This, together with a loss modulus (G&) remaining lower than G" all over the swept frequency range, indicates the presence of a network of entangled CNT clusters with a pseudo-solid-like behaviour.…”