Elastomeric ethylene copolymers with carbon nanostructures having tailored strain sensor behavior and their interpretation based on the excluded volume theory

Abstract

Two ethylene/1-butene thermoplastic elastomer copolymers were melt mixed with either multiwalled carbon nanotubes (CNTs) or thermally reduced graphite oxide (TrGO) resulting in piezoresistive composite materials. The effect of the polymer matrix, carbon nanostructure and filler concentration on the electrical behavior of the sensors was analyzed. The percolation process confirmed the relevance of these parameters as different thresholds were found depending on both the matrix and the filler. For instance, composites based on TrGO presented higher percolation thresholds than those based on CNTs. Regarding the strain sensor behavior of the electrically conductive composites, by using a matrix with a low amount of 1-butene comonomer, higher resistance sensitivities were observed compared with the other matrix. Noteworthy, composites based on TrGO filler presented strain sensitivities one order of magnitude higher than composites based on CNT filler. These results are explained by the excluded volume theory for percolated systems. Based on these findings, polyethylene piezoresistive sensors can be designed by a proper selection of polymer matrix, filler concentration and carbon nanoparticles.