Strengthened, thermoreversible and conductive rubber with dual dynamic networks for strain sensors†

Endowing conductive composites with thermoreversible properties is important for improving the stability and extending the service life of the material and are in line with today's concept of green chemistry. In this study, thermoreversible conductive XNBR-based composites with excellent mechanical, reprocessable and conductive properties were prepared via a simple and feasible emulsion blending technique. Carbon black was used as a conductive filler, and epoxy resin and zinc chloride (ZnCl₂) were added as a crosslinking agent into carboxylated nitrile butadiene rubber (XNBR) through latex mixing. In particular, the –COOH group on the XNBR molecular chain forms β-hydroxy ester and ionic bonds with epoxy groups and Zn²⁺, respectively, constituting a dual dynamic network structure. The prepared rubber has a tensile strength of 10.81 MPa, an elongation at break of more than 300%, and a conductivity of up to 0.0102 S m⁻¹. Moreover, the composite has a high gauge factor (18.4) under fairly large strain (100%) and can accurately detect human activities, thus showing great potential as strain sensors. In addition, the tensile strength and electrical conductivity of the repeatedly processed material can reach 101% and 60%, respectively, of the original sample. Furthermore, based on its stretchability and conductivity, the composite is sensitively capable of capturing variation in strain, which shows great potential for application in strain sensors.