Search

Magnetorheological elastomers (MREs) are smart materials whose mechanical properties can quickly respond to changes in the external magnetic field. This phenomenon is known as the magnetorheological (MR) effect and is the key to the application of magnetorheological elastomers. Previous studies have found that the interface between magnetic particles and elastomers is a critical factor that influencing the MR effect of MREs. To improve the interfacial interaction between silicone rubber (SR) and carbonyl iron (CI) particles, in the MREs considered in this work, CI particles were subjected to surface modification through polydopamine (PDA) deposition and n-dodecyltrimethoxysilane (DTMS) grafting. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the successful deposition of PDA@DTMS coating layer with a thickness of about 30.6 nm. The tensile strength of anisotropic MREs increased by 31.5% after surface modification of CI particles. The study of magnetic field induced changes in viscoelastic properties showed that CI-PDA@DTMS based MREs exhibited a superior MR effect to the CI-based MREs.

In this work, polyphenolic extract from walnut green husks (denoted as walnut polyphenols), which is an abundant agroindustrial residue/waste, was used to modify barium titanate (BT) particles in the preparation of silicone rubber (SR) based dielectric elastomer (DE) composites with enhanced electromechanical performance. By employing walnut polyphenols modification, the dispersibility of BT particles in the SR matrix and the compatibility between BT and SR were greatly improved, which resulted in enhanced mechanical performance of the DE composites. Dielectric property measurement showed that DE composites containing walnut polyphenols modified BT particles (WNBT) had higher dielectric constants and lower dielectric losses than that of DEs with unmodified BT particles. Furthermore, it was found that the walnut polyphenols modification resulted in decreased dielectric loss tangent of the DE composites, suggesting an improved compatibility between the modified BT particles and SR. Finally, the static and dynamic electromechanical performance of the DE composites were evaluated. The SR/5% WNBT composite achieved the highest actuated area strain of 38% among the SR based composites used in this work. Moreover, the actuated area strain of SR/WNBT composites exhibited excellent electromechanical stability during the application of cyclic voltage signals.