An original combined method for electrical conductivity measurement of polymer composites under extensional deformation

Abstract

International audienc

A model for the electrical conductivity variation of molten polymer filled with carbon nanotubes under extensional deformation

“…The network destruction is more complex and is intimately linked to the filler network structure. In fact, it has been observed that under shear deformation at large shear rates [16] or under extensional deformation [17], the agglomerates are stretched and orient in the deformation direction. The aggregates network morphology changes in response to strains and, more precisely, its response is linked to its initial morphology [15,18,19].…”

Electrical conductivity under shear flow of molten polyethylene filled with carbon nanotubes: Experimental and modeling

“…[ 31 ] For example, in elongation, the CNTs are strained apart from each other, destructing fillers connections hence triggering a conductor to insulator transition. [ 20 ] Conversely, in the case of shear deformation, both increase and decrease in conductivity can be achieved. During a shear experiment, the effective concentration evolves monotonically depending on the initial network structure and the applied deformation.…”

“…[ 16 ] Electrical properties rely on a continuous network composed by contacts between small aggregates and individual CNTs. [ 17‐20 ] A contact here is considered an electrical contact, which means an electrical charge transfers between CNT by any mechanism (including tunnel effect). [ 21‐23 ] This complex grid can be modified during processing steps (thermoforming, mold injection, extrusion, and so on) by the applied mechanical deformation.…”

“…[ 21‐23 ] This complex grid can be modified during processing steps (thermoforming, mold injection, extrusion, and so on) by the applied mechanical deformation. [ 20, 24‐26 ] For cost reasons but also in‐use mechanical properties, a very low CNT content is desired but this leads to electrical properties very dependent on processing steps and turns the manufacturing of conductive polymer composites into an industrial challenge. [ 27 ]…”

“…They assumed that CNTs, whether they are regrouped as agglomerates or just individual, take part in the sample's electrical conductivity as long as they are connected to the interconnected network. [ 20 ] In other words, more than counting CNTs that are connected to each other by contacts, the model was developed by considering an efficient part of the volume fraction of CNTs and a non‐efficient part. The efficient part contains the CNTs incorporated in the percolation network (providing an electrical path from one surface of the material to the other).…”