Characterization of Graphene–Ethylene Propylene Diene Monomer/Butyl Rubber Hybrid Nanocomposite Strain Sensor

Abstract

This study focuses on developing an elastic nanocarbon-reinforced ethylene propylene diene monomer (EPDM)/butyl rubber (IIR—isobutylene isoprene rubber) hybrid nanocomposite strain sensors with enhanced conductivity for human motion detection applications. The multiwalled carbon nanotubes (MWCNTs) and graphene (GR) sheets were incorporated as reinforcements in the matrix using the solution blending technique to improve the sensing capabilities. The effect of different weight percent loading of GR has been investigated on the morphology and conductivity of GR/MWCNTs-EPDM/IIR hybrid nanocomposite, keeping the weight percent loading of MWCNTs constant. The FE-SEM analysis, TEM analysis, Raman spectroscopy, and FT-IR spectroscopy of the synthesized samples revealed the distributed formation of the GR/MWCNTs network along with good interfacial adhesion with the matrix. It is evident from the TEM images that MWCNTs bridged the gap between GR sheets, whereas GR formed interconnection sites between the MWCNTs. Thus, the hybrid nanofillers better promote the formation of local conductive paths leading to improved electrical conductivity at low percolation thresholds. The tensile strength and elongation at the break of the composite samples were also analyzed. The optimum tensile strength and elongation at break were obtained as 8.58 MPa and 78%, respectively, for the sample with 7.5 wt.% MWCNT and 5 wt.% GR reinforcement. The conductivity of the prepared specimen was examined using the 4-probe method. The results show that the conductivity of specimens with 5 wt.% and 7.5 wt.% GR increased by 68.75% and 154.16%, respectively, as compared to the specimen with 3.5 wt.% GR. This increase in conductivity can be attributed to the improvement in the percolation pathways. The resistance-time response and repeatability of the sensor were tested by doing manual folding for 1000 cycles. The performance of the hybrid nanocomposites makes it a promising candidate for strain sensor applications in human motion such as finger fold and wrist bend.