Recently, dielectric elastomer actuators (DEA) have emerged as one of the most promising materials for use in soft robots. However, DEA needs a high operating voltage and high mechanical properties. By increasing the dielectric constant of elastomeric materials, it is possible to decrease the operating voltage required. Thus, elastomeric composites with a high dielectric constant and strong mechanical properties are of interest. The aim of this research was to investigate the effect of titanium dioxide (TiO2) content ranging from 0 to 110 phr on the cure characteristics, and physical, dielectric, dynamic mechanical, and morphological properties of acrylonitrile butadiene rubber (NBR) composites. The addition of TiO2 reduced the scorch time (ts1) as well as the optimum cure time (tc90) but increased the cure rate index (CRI), minimum torque (ML), maximum torque (MH), and delta torque (MH - ML). The optimal TiO2 content for maximum tensile strength and elongation at break was 90 phr. Tensile strength and elongation at break were increased by 144.8% and 40.1%, respectively, over pure NBR. A significant mechanical property improvement was observed for TiO2-filled composites due to the good dispersion of TiO2 in the NBR matrix, which was confirmed by scanning electron microscopy (SEM). Moreover, incorporating TiO2 filler gave a higher storage modulus, a shift in glass transition temperature (Tg) to a higher temperature, and reduced damping in dynamic mechanical thermal analysis (DMTA). The addition of TiO2 to NBR rubber increased the dielectric constant of the resultant composites in the tested frequency range from 102 to 105 Hz. As a result, TiO2-filled NBR composite has a high potential for dielectric elastomer actuator applications.
Keywords: acrylonitrile butadiene rubber; dielectric properties; mechanical properties; titanium dioxide.