Enhanced electromechanical behaviours of epoxidized natural rubber composites via constructing non-covalent and covalent bonds by using tannic acid and Si747

Abstract

Dielectric elastomer actuators (DEAs) are attractive for use in energy harvesting devices and soft robotics. In this study, barium titanate (BaTiO3) nanoparticles (NPs) were modified by tannic acid (TA) and 3-mercapto-propyl-ethoxy-bis(tridecyl-pentaethoxy-siloxane) (Si747) (denoted as BaTiO3-TA-Si747) via non-covalent and covalent modification. Then the as-prepared BaTiO3-TA-Si747 were incorporated into the epoxidized natural rubber (ENR) matrix (denoted as BaTiO3-TA-Si747-ENR) to prepare ENR DEA, aiming at obtaining high actuated strains at a low electric field. The TA and Si747 exhibited the partial polymeric flexibility on the surface of BaTiO3 NPs, and Si747 participated in the cross-linking reaction of ENR, resulting in a low Young's modulus and a high sensitivity coefficient of the BaTiO3-TA-Si747-ENR composites. Furthermore, TA and Si747 enhanced the interfacial interaction and compatibility between BaTiO3 NPs and the ENR matrix, which decreased the dielectric loss of the ENR composites and increased the efficiency of the energy conversion. A high actuated strain of 14.18% at 57.2 kV/mm was demonstrated by the 10 phr BaTiO3-TA-Si747-ENR composite, whereas pure ENR exhibited a value of 10.42% at 51.4 kV/mm. The combination of non-covalent and covalent surface modification using TA and Si747 is highly efficient, and it is expected to be applied at a large scale in industrial production.