DC and AC Conductivity of Carbon Nanotubes−Polyepoxy Composites

Abstract

The dc and ac conductivities of carbon nanotubes-polyepoxy composites have been investigated from 20 to 110°C in the frequency range 10 -2 -10 6 Hz as a function of the conductive weight fraction p ranging from 0.04 to 2.5 wt %. The frequency dependence of the measured conductivity obeys the universal dynamic response (UDR): a dc plateau followed, above a critical frequency ωc,b yt h eω s power law with exponent s ∼ 0.6-1. The dc conductivity follows a percolation scaling law: σdc ∝ (ppc) t with pc ) 0.3 wt % and t ) 1.4-1.8, according to the temperature. σdc reached 10 -4 S/cm for 2.5 wt % CNTs content and increases with increasing temperature. Considering a biased random walk in three dimensions approach, we may explain the scaling law of ω c with p and its proportionality to σdc. The universality of ac conduction in carbon nanotubes-polymer composites is examined by the construction of master curves.

Effect of pre and Post-Dispersion on Electro-Thermo-Mechanical Properties of a Graphene Enhanced Epoxy

“…The presence of bromine caused the formation of ionic and covalent bonds with the matrix, improving the flexibility of the composites, and the electrical conductivity. However, some studies [25,[48][49][50] have shown that the surface functionalisation of GNP can also decrease the electrical properties of the nanocomposites compared to when unmodified GNP is used. As the electron displacement is known to occur mainly on the surface of graphene, highly functionalising the surface might increase the mechanical properties but decrease the electrical properties of the final product.…”

Relationship between dispersion metric and properties of PMMA/SWNT nanocomposites

“…Since the discovery of carbon nanotubes (CNTs) by Iijima [1], extensive studies have been conducted exploring their unique electronic, thermal, optical, and mechanical properties and their potential use in greatly enhancing the physical properties of polymer nanocomposites [2,3,4,5,6], as summarized in recent review articles [7,8]. The outstanding properties are in part attributed to their extremely high aspect ratio (lengthto-outer diameter ratio) of up to 1000.…”

Control of multiwall carbon nanotubes dispersion in polyamide6 matrix: An assessment through electrical conductivity

“…Apart from mechanical reinforcement [2,3], one of the key interests is to develop conductive polymer composites [4][5][6] preferably at low concentration of CNT utilizing their high aspect ratio (L/D) for numerous applications, which include antistatic devices, capacitors and materials for EMI shielding. However, with few exceptions [7][8][9] uniform dispersion of CNT in polymer matrix is restricted due to aggregate formation irrespective of the techniques employed for composite preparation. This is presumably due to (i) strong inter-tube van der Waals interaction and (ii) lack of interfacial interaction between the polymer and the CNT.…”

“…However, the electrical percolation threshold in polymer/CNT composites is found to be much higher in case of thermoplastic matrices [13,14] as compared to theoretically predicted percolation threshold considering L/D of CNT as one of the critical parameters which is otherwise found to be close to the predicted values in thermoset (epoxy, polyimide etc.) filled system [7][8][9]. Additional complexity arises in case of semi-crystalline matrices (polypropylene [14], polyethylene [15], polyamides [16]) where it is envisaged that the dispersion of CNT is significantly affected due to the crystallization induced phase separation and subsequent rejection of CNT by the advancing crystalline fronts.…”