Superposition approach for description of electrical conductivity in sheared MWNT/polycarbonate melts

Abstract

The theoretical description of electrical properties of polymer melts, filled with attractively interacting conductive particles, represents a great challenge. Such filler particles tend to build a network-like structure which is very fragile and can be easily broken in a shear flow with shear rates of about 1 s–1. In this study, measured shear-induced changes in electrical conductivity of polymer composites are described using a superposition approach, in which the filler particles are separated into a highly conductive percolating and low conductive non-percolating phases. The latter is represented by separated well-dispersed filler particles. It is assumed that these phases determine the effective electrical properties of composites through a type of mixing rule involving the phase volume fractions. The conductivity of the percolating phase is described with the help of classical percolation theory, while the conductivity of non-percolating phase is given by the matrix conductivity enhanced by the presence of separate filler particles. The percolation theory is coupled with a kinetic equation for a scalar structural parameter which describes the current state of filler network under particular flow conditions. The superposition approach is applied to transient shear experiments carried out on polycarbonate composites filled with multi-wall carbon nanotubes

Viscoelastic melt rheology and time–temperature superposition of polycarbonate–multi-walled carbon nanotube nanocomposites

“…Several authors have specifically studied the properties of PC-MWCNT composites, focusing on the melt rheology (Pötschke et al 2002;Du et al 2004;Abdel-Goad and Pötschke 2005;Sung et al 2005;Alig et al 2008), the mechanical response (Eitan et al 2006;Fornes et al 2006;Satapathy et al 2007), and the electrical properties (Du et al 2004;Sung et al 2006;Alig et al 2008;Saphiannikova et al 2012). Some authors have employed a combination of characterisation methods, such as the simultaneous electrical and rheological measurements of Alig et al (2008) and Zeiler et al (2010).…”

Thermally Drawn Elastomer Nanocomposites for Soft Mechanical Sensors

“…[ 34,43 ] It is known to be strongly dependent on the processing conditions, most importantly the temperature as it alters significantly the viscosity of the polymer and thus the shear forces acting on the filler aggregates. [ 44 ] As presented in Figure 1d, above the crossover temperature, the complex viscosity of SEBS rapidly decreases with increasing temperature, and transitions from 1.6 × 10 5 Pa s at 110 °C to 1.5 × 10 4 Pa s at 160 °C. Therefore, by increasing the drawing temperature, stresses transferred to the filler network may be lower, reducing the probability of conductive pathways destruction, and therefore preserving the network integrity.…”

Effect of ultrasonic treatment on the properties of multiwalled carbon nanotubes – polymethylmethacrylate composites: Effect of applied voltage and pressure on conductivity of the composites

“…A significant deviation of the percolation threshold either to larger or to smaller values indicates CNT structuring in the composites (existence of preferable nanotube orientation, presence of aggregates, surface filling of the matrix structural elements as in ceramic matrices, etc.) or the interaction of the composite matrix with the CNT surface resulting in partial blocking of contacts between individual nanotubes (as in polymer matrices) [15][16][17]. Coagulation technique is one of the methods used for production of composites with MWCNTs.…”