Flexible and stretchable conductive materials represent an emerging class of advanced functional materials. Among them, rubber–carbon composites have attracted considerable attention for their potential in fabricating flexible, stretchable conductive systems. Carbon fiber (CF), as a representative carbon material, offers advantages such as large aspect ratio and the ability to form effective conductive networks through interconnection. However, commercially available CF is predominantly supplied in bundled form. During compounding with conventional rubber matrices, high shear forces are typically required to achieve uniform dispersion, often leading to severe CF breakage and a consequent decline in the electrical conductivity of the composite. In this study, a low-viscosity, self-crosslinking, two-component room-temperature vulcanizing liquid silicone rubber (LRTV) was employed as the matrix. To overcome the dispersion issues of bundled CF, short-cut CF bundles were treated with air plasma to induce CF fluffing, thereby improving their uniform distribution within the LRTV matrix. Additionally, surface modification of carbon black (CB) with silane coupling agents was performed to eliminate the adverse effect of oxygen-containing functional groups on composites, which had been found to inhibit the self-crosslinking process of LRTV. Using a simple and reliable injection molding process, high-performance flexible and stretchable conductive composites were successfully prepared. The synergistic influence of CF and CB on the electrical conductivity of the composites was systematically investigated. Results showed that the electrical conductivity of the composites was highly sensitive to CF content. At a fixed CB content of 3 wt%, increasing the CF content from 1 wt% to 4 wt% led to a six-fold enhancement in conductivity. In contrast, varying CB content had a minimal impact. At a fixed CF content of 3 wt%, increasing the CB content from 1 wt% to 5 wt% only increased the conductivity by 0.11 S/m. Further studies on the electrical response of the composites under large-strain cyclic deformation revealed that samples with 1 wt% CF and 3 wt% CB exhibited periodic fluctuations in conductivity in response to deformation, demonstrating promising potential for applications in flexible sensors. On the other hand, the composite containing 4 wt% CF and 3 wt% CB exhibited a smooth conductivity profile with minimal variation, indicating its suitability for flexible conductor applications. This work presents a novel strategy for the development of flexible and stretchable conductive electrodes or sensor materials, offering new opportunities in wearable electronics.

Keywords: stretchable conductive, composites, silicone rubber, carbon materials.