Rheological percolation, gel-like behavior and electrical conductivity of multi- walled carbon nanotubes filled ethylene-vinyl acetate copolymer/acrylonitrile- butadiene rubber nanocomposites

Abstract

Rheological percolation, gel-like behavior and electrical properties of multi-walled carbon nanotubes (MWCNTs) filled ethylene-co-vinyl acetate/acrylonitrile-butadiene copolymer blends containing 0-7 wt% MWCNTs were studied. The Winter-Chambon criterion validity was evaluated for gelation of the system. The rheological and electrical percolation threshold, gel point (Pg), relaxation exponent (n), gel strength (Sg) and the fractal dimension (df) at the gel point were calculated. The formation of physical gel and rheological percolation threshold were both found to occur at 1 wt% MWCNTs concentration. Based on the df value determined, it was revealed that the system behaved similar to the one in which the excluded volume interactions were nearly screened. It was also found that the storage modulus (G') near the Pg followed a power law scaling relationship in the form G'=8257ε1.36 where ε=|P-Pg|/Pg is the distance from Pg. The electrical conductivity of the nanocomposites increased with the increase in MWCNTs loading after the nanofillers content surpassed a certain value. A schematic model was proposed to demonstrate electrical conduction with the increase in MWCNTs concentration. The excluded volume and hard core models were also employed to estimate the average aspect ratio of the nanofillers embedded in the system.