Study of a Polymer Composite with Carbon Nanotubes and a Mixed Filler Using a Composite Piezoelectric Oscillator at a Frequency of 100 kHz

This article presents an investigation of the thermomechanical properties of silicone elastomer-based polymer composites modified with carbon nanotubes (CNTs) and mixed fillers (CNTs, bronze, graphite). The primary technique employed was the composite piezoelectric oscillator (CPO) method at approximately 100 kHz. This approach enabled precise measurements of the polymers’ forced oscillation frequency and logarithmic damping decrement (internal friction) across a wide temperature range (80–300 K). The application of this method is novel for this specific class of materials. Scanning electron microscopy confirmed the uniform distribution of the fillers within the polymer matrix. Differential scanning calorimetry (DSC) showed that the fillers modify the thermal stability of the composite. The systematic decrease in the enthalpy of the endothermic decomposition peak suggests a retardation of degradation kinetics, most likely due to a barrier effect of the filler network. Electrical measurements revealed a distinct contrast: the hybrid composite exhibited a frequency-independent conductivity plateau (~1.8 × 10−1 S/m), confirming a robust percolating network, unlike the strong frequency dependence observed for the CNT-only composite. Research shows that the fillers effectively suppress relaxation processes linked to crystallization (205–215 K) and glass transition (165–170 K), as evidenced by a significant reduction in the amplitude of the corresponding internal friction peaks. The most pronounced effect was observed in the composite with mixed fillers, attributable to a synergistic effect between constituents. Furthermore, amplitude-dependent internal friction was found to occur predominantly below the glass transition temperature. The primary objective of the present study is to investigate the dynamic mechanical and damping behavior of CNT-filled silicone composites with mixed fillers under high-frequency loading, using the CPO method. These findings demonstrate the potential for tailoring the stiffness and damping characteristics of these composites for advanced applications in soft robotics and portable electronics.