Dynamic electrical and mechanical properties of epoxy/silver nanowires composites

Abstract

The aim of this work is to study electrically conductive composites from an epoxy matrix loaded with silver nanowires (AgNWs). Dynamic mechanical analysis (DMA) and dynamic dielectric spectroscopy (DDS) were used to study the molecular mobility of the epoxy matrix and its epoxy/AgNWs composites. The influence of the epoxy/amine ratio on the macroscopic properties was analyzed. The loss modulus of the epoxy matrix highlights two major relaxations, β and α. The β relaxation is due to the localized mobility initiated by hydroxyl groups. The α trelaxation is the anelastic effect liberated at the glass transition. The introduction of a small amount of AgNWs (<8 vol%) has practically no influence on the mechanical properties of the glassy state. For the rubbery state, AgNWs cause an increase in the storage modulus as a function of the filler content. The loss modulus profile is modified: The 0.25emω relaxation due to heterogeneities of the 3D network is observed independently from the hydration level of composites. The magnitude of the α mode is increased due to the stick–slip phenomenon. Moreover, it is shifted toward lower temperatures upon the introduction of AgNWs. In other words, the activation enthalpy decreases for both modes. Electrical study through DDS and conductivity measurement of epoxy/AgNWs composites shows the consequence of a lower relative degree of conversion caused by the insertion of AgNWs. Epoxy/AgNWs composites allow us to obtain one of the highest values of the electrical conductivity for polymer‐based composites without any drastic evolution of mechanical properties.

One‐step elaboration of flexible transparent conductive electrodes from silver nanowires/polymer nanocomposites

“…22 The percolation threshold ( p c ) corresponds to the large shift in electrical conductivity and occurs above this critical concentration of conductive particles. The percolation threshold value is linked to the aspect ratio 5,23 for the same dimensionality of the percolated network. This relationship between AgNWs morphology and electrical properties has been reported in the literature 5,6,[23][24][25][26][27] and has conclude that ultra-long AgNWs has a preponderant role to reduce the number of wires needed to create a conductive network thereby lowering the percolation threshold.…”

“…The percolation threshold value is linked to the aspect ratio 5,23 for the same dimensionality of the percolated network. This relationship between AgNWs morphology and electrical properties has been reported in the literature 5,6,[23][24][25][26][27] and has conclude that ultra-long AgNWs has a preponderant role to reduce the number of wires needed to create a conductive network thereby lowering the percolation threshold. For this reason, the effective aspect ratio was introduced to take in account this point.…”

“…For this reason, the effective aspect ratio was introduced to take in account this point. 5,23 The global percolating network was obtained with the mix of long and short nanowires. The effective aspect ratio is the more accurate parameter to describe the role of the morphology on electrical properties like the percolation threshold.…”

“…The universal exponent t value, confirmed that particles are oriented in a plane (two-dimensional system). Through an extrapolation of excluded volume, Balberg demonstrated that for 2D systems, the charge rate of conductive particles at the percolation threshold multiplied by their aspect ratio is equal to a constant value 5,23 :…”