Stochastic percolation model for the effect of nanotube agglomeration on the conductivity and piezoresistivity of hybrid nanocomposites

Abstract

Agglomeration is a common occurrence in polymer nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNP) as fillers and usually leads to a reduction of electrical and mechanical properties of the composites. In this paper, we utilize a two-dimensional Monte Carlo percolation model for monofiller and hybrid nanocomposites to examine the effect of CNT agglomeration on electrical and electromechanical behavior of the nanocomposites. We generate microstructures of tunneling network with different agglomerate content, agglomerate morphology (equiaxed to rope-like), and agglomerate filler density to parametrically study the effects of agglomeration on percolation, conductivity and piezoresistivity. Electron tunneling in the network is modeled as the primary mechanism for electrical percolation. Our models indicate that high level of agglomeration leads to a systematic increase of the percolation threshold with a decrease of the conductivity, while low agglomeration level with low filler density within agglomerates improves the percolation and conductivity behavior. The addition of GNP as second filler in hybrid composites leads to an improvement in conductance and piezoresistivity despite the presence of CNT agglomeration.