Copolyester nanocomposites based on carbon nanotubes: reinforcement effect of carbon nanotubes on viscoelastic and dielectric properties of nanocomposites

Abstract

Nanocomposites based on an amorphous copolyester, poly(ethylene glycol-co-cyclohexane-1,4dimethanol terephthalate) and carbon nanotubes were fabricated using a simple melt processing technique. The reinforcement effect of carbon nanotubes in the copolyester was investigated experimentally using different approaches based on dynamic mechanical analysis, rheology and dielectric analysis. The nanocomposites show a mechanical reinforcement effect with significant increase in the stiffness especially in the rubbery regime with increasing nanotube content. An increase in T g and a decrease in damping are seen, which are derived from the presence of a percolating superstructure of the filler. Rheological experiments show an increase in storage modulus up to four orders of magnitude. Viscolelastic characterization shows that the percolation threshold is at 3 wt% of nanotubes. Dielectric relaxation spectroscopy confirms the presence of this percolating structure. We conclude that the responses of both rheological and electrical properties are different, although both are related to the formation of a percolating network superstructure of the filler.

Different filler effect of carbon nanotube and graphene nanoplatelet in the poly(arylene ether nitrile) matrix

“…However, when the GN content is over 1 wt%, the flow regime of PEEN/GN composites is significantly altered at low frequencies and a pseudo‐solid‐like behavior is more visible. This phenomenon has also been observed in both polymer/CNT and polymer/GN systems, and is mainly due to the existence of interactions between the fillers and polymer matrices , . With addition of more CNTs and GNs, however, the dependence on low frequency weakens and the slope of G ′ becomes flat.…”

“…Figure shows the complex viscosity (η*) of neat PEEN and PEEN composites with different nanocarbon contents. As can be seen in Figs (a) and (b), the η* of neat PEEN shows little frequency dependence and behaves almost like a Newtonian fluid, since the polymer chain is fully relaxed at all frequencies , . As the filler content increases, the slope of η* slightly increases, but a dramatic increase happens when CNTs are over 1 wt% or GNs are above 0.5 wt%.…”

“…More importantly, as can be observed in Figs (a)–(c), at low frequencies the sudden η* increase in the PEEN/CNT composites happens at 2 wt% CNT loading, but for PEEN/GN composites 1 wt% GN content exhibits the marked η* increment. The sudden η* change at low frequencies indicates a transition from viscoelastic liquid to solid‐like behavior, and this transition behavior is attributed to the formation of a percolated structure by the fillers , …”

“…Generally, the thermal properties of polymer/filler composites can reflect the inner movements of the polymer chains affected by the fillers . Moreover, oscillatory shear rheology is of practical and basic importance since it is related to composite processing, dynamics, the structure–property relationship and the interaction between filler and polymer in composite systems , . Rheological behavior at high frequencies can be employed to estimate the influence of fillers on the processing properties, while the low frequency behavior is sensitive to the structure of the composites, which can be used to obtain information about the percolation state of fillers and interactions between fillers and polymers within the composites.…”

The properties (rheological, dielectric, and mechanical) and microtopography of spherical fullerene‐filled poly(arylene ether nitrile) nanocomposites

“…5 To date, nanocarbons of quasi-one-dimensional carbon nanotube (CNT) and two-dimensional graphene nanosheet (GN) have been mostly used to prepare polymer nanocomposites and their mechanical, thermal, electrical, morphological, especially dielectric, and rheological properties were studied. 8 On the contrary, zero-dimensional fullerene with a special hollow cage structure can be used to prepare low dielectric constant materials. In addition, the general results found that there is a dielectric transition regarding GN, which is usually larger than the rheological percolation threshold, but for CNT the dielectric transition has not been observed.…”