Nanocarbon Black and Molybdenum Disulfide Hybrid Filler System for the Enhancement of Fracture Toughness and Electromechanical Sensing Properties in the Silicone Rubber-Based Energy Harvester

Recently, hybrid fillers have been found to be more advantageous in energy-harvesting composites. This study investigated the mechanical and electromechanical performances of silicone rubber-based composites made from hybrid fillers containing conductive nanocarbon black (NCB) and molybdenum disulfide (MoS₂). A hybrid filler system containing only 3 phr (per hundred grams of rubber) MoS₂ and 17 phr NCB provided higher fracture strain, better tensile strength, and excellent toughness values compared to the 20 phr NCB-only-filled and 5 phr MoS₂-only-filled rubber composites. The chemical cross-link densities suggest that NCB promoted the formation of cross-links, whereas MoS₂ slightly reduced the cross-link density. The higher mechanical properties in the hybrid filler systems suggest that the filler particles were more uniformly distributed, which was confirmed by the scanning electron microscope study. Uniformly distributed filler particles with moderate cross-link density in hybrid filler systems greatly improved the fracture strain and fracture toughness. For example, the hybrid filler with a 17:3 ratio of NCB to MoS₂ showed a 184% increment in fracture toughness, and a 93% increment in fracture strain, compared to the 20 phr NCB-only-filled composite. Regarding electromechanical sensing with 2 kPa of applied cyclic pressure, the hybrid filler (17:3 CB to MoS₂) performed significantly better (~100%) than the 20 phr NCB-only compound. This may have been due to the excellent distribution of conducting NCB networks and piezoelectric MoS₂ that caused symmetric charging–discharging in the toughened hybrid composite. Thus, hybrid composites with excellent fatigue resistance can find dynamic applications, such as in blood pressure measurement.