Styrene-butadiene rubber-based nanocomposites toughened by carbon nanotubes for wide and linear electromechanical sensing applications

The contribution from specific interactions between rubber and filler sometimes plays a crucial role in the mechanical reinforcement and electromechanical sensitivities of rubber composites. This research explores the physical, mechanical, and electromechanical properties of styrene-butadiene rubber (SBR) composites reinforced with carbon nanotubes (CNTs). Mechanical, thermodynamic, and scanning electron microscopy studies reveal that CNTs primarily enhance the mechanical properties through physical interactions with the rubber. Notably, pi-stacking interactions between the aromatic pi-electrons in SBR and the delocalized pi-electrons in CNTs contribute to significant improvements in mechanical strength. For instance, adding 4 phr (per hundred grams of rubber) of CNTs results in an impressive 871% increase in fracture toughness compared to unfilled rubber. These composites also exhibit remarkable stress and strain improvements even with small amounts of CNTs, making them suitable for robust strain sensing applications. Specifically, the composite containing 3 phr of CNTs demonstrates superior strain sensitivity (2.87 < GF < 48.62), a wide detection range (0% < Delta epsilon < 187%), and excellent linearity (0.927 < R-2 < 0.995). Lower CNT content enhances sensitivities but reduces overall linearity, while higher CNT content improves linearity but decreases sensitivity. Moreover, these composites perform exceptionally well under compressive forces, even at a 0.5 N applied force. Given their excellent response to mechanical forces and strain, these composites hold promise for applications like electronic skin, strain sensors, and energy-harvesting devices.Highlights Carbon nanotubes (CNTs) were used as reinforcing fillers in SBR composites. CNTs significantly improve physical, mechanical, and electrical properties. Primarily, pi-stacking may be involved in enhancing these properties. The composites exhibit strong strain and force-sensing capabilities. These composites could be valuable for wearable electronics in the future.