Development of Silicone Rubber-Multiwalled Carbon Nanotube Composites for Strain-Sensing Applications: Morphological, Mechanical, Electrical, and Sensing Properties

This study presents a comprehensive investigation on the fabrication and characterization of piezoresistive elastomeric strain sensors using multiwalled carbon nanotubes (MWCNTs) incorporated into a silicone rubber matrix. Through meticulous experimentation and theoretical modeling, the study elucidates the intricate relationship between MWCNT concentration, mechanical properties, and electrical conductivity within the composite materials. The research reveals that composite formulations with MWCNT concentrations slightly above the percolation threshold exhibit superior strain-sensing properties. Specifically, composites containing 2 phr of MWCNTs demonstrate a remarkable gauge factor of 225, indicating enhanced sensitivity compared with higher MWCNT loadings. Mechanical testing using a tensile testing machine elucidates the complex interplay between MWCNT loading and tensile properties. However, subsequent enhancements in tensile properties with increasing MWCNT content suggest improved dispersion and reinforcing effects, highlighting the potential for tailored mechanical performance. The investigation of DC conductivity demonstrates a significant increase with rising MWCNT concentrations, indicative of the formation of conductive networks as MWCNTs reach the percolation threshold. Enhanced charge transport and constructive interface interactions facilitate efficient electron flow through the composite, which is crucial for applications requiring electrical conductivity. Moreover, the analysis of dielectric permittivity reveals its concentration-dependent increase, attributed to the large surface area of MWCNTs promoting stronger interactions with the matrix and enhanced polarization under electric fields. Drastic changes in AC conductivity at lower frequency levels within the percolation region suggest influences of dielectric relaxation, polarization effects, and formation of conductive paths. This study underscores the potential of MWCNTs-silicone rubber composites as versatile materials for advanced strain-sensing applications, offering tunable mechanical and electrical properties tailored to specific requirements.