Preparation of waterborne epoxy resin based graphene sensor and its smart properties

To meet the demand for new sensors in the intelligent transformation and upgrading of engineering structures, using waterborne epoxy resin (WER) as the matrix, reduced graphene oxide (RGO) as the conductive filler, and cellulose nanofiber (CNF) as the dispersant, RGO-CNF/WER sensor was prepared using a solution blending method. The mechanical, electrical and smart properties were tested and analyzed, and a smart response model considering strain rate effects was established. The results indicated that CNF can effectively carry RGO for uniform dispersion in water, assisting in the formation of a three-dimensional conductive network in WER. The percolation threshold of RGO is about 0.15%. The sensor can withstand over 70% tensile strain, and its initial strain resistance response is unstable. After about 4 pre-stretching cycles, the conductive network tends to be perfected, showing good repeatability and recoverability. When the strain of the sensor is less than 4%, the resistance change rate is positively correlated with the strain, and the sensitivity coefficient can reach 32. After the strain exceeds 4%, the resistance change rate increases exponentially. The response strength of strain resistance increases with the increase of strain rate.