Shear induced electrical behaviour of conductive polymer composites

Abstract

Abstract. The time-dependent electrical resistance of polymethylmethacrylate containing carbon black was measured under oscillatory shear in the molten state. The electrical signal was oscillating exactly at the doubled frequency of the oscillatory shear deformation. Moreover, the experimental results gave a hint to the development of conductive structures in polymer melts under shear deformation. It was shown that the flow induced destruction of conductive paths dominates over the flow induced build-up in the beginning of the shear deformations. However, for longer times both competitive effects reach a dynamic equilibrium and only the thermally induced build-up of pathways influences the changes in the composite resistance during the shear. Furthermore, the oscillating electrical response depends clearly on the deformation amplitude applied. A simple physical model describing the behaviour of conductive pathways under shear deformation was derived and utilized for the description of the experimental data.

Mapping the Electrical Conductivity of Poly(methyl methacrylate)/Carbon Black Composites Prior to and after Shear

“…Conductive polymer composites (CPCs), consisting of an insulating polymer and electrical conductive fillers such as carbon black (CB) or carbon nanotubes, have been intensively studied because of their unique electrical and mechanical properties. − Recently, there has been increasing interest in so-called coupled rheological and electrical experiments because the electrical properties of CPCs are very sensitive to the changes of the conductive structure induced by mechanical deformation. − Furthermore, the electrical properties of CPCs depend on the size and shape of the fillers as well as their spatial distribution in the polymer matrix. , Moreover, because of the strong intermolecular van der Waals interactions among the CB aggregates, which lead to the formation of conductive structures, it is rather difficult to disperse CB in a polymer matrix in a uniform fashion. Accordingly, it remains a question of whether there is a certain dependence of the electrical conductivity on the radial position for disklike CPC samples prior to shear and after exposure to shear.…”