Frequency-dependent dielectric and impedance properties of TPU-graphene nanocomposites

The development of multifunctional polymer nanocomposites with tunable electrical properties is vital for nextgeneration flexible electronics applications. In this study, we present a systematic investigation into the effects of graphene content on the dielectric, morphological, mechanical, and thermal properties of thermoplastic polyurethane (TPU) nanocomposites. Comprehensive characterization was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile testing, thermogravimetric analysis (TGA), and frequency-dependent dielectric and impedance measurements. TPU films with varying graphene contents (0 %, 3 %, 5 %, 7 %, and 10 %) were fabricated via solvent casting. The results show that adding more graphene increases the interfacial polarization and helps form conductive pathways in the TPU matrix. At higher graphene concentrations, dielectric and impedance results clearly show a transition from capacitive (energystoring) to conductive (current-carrying) behavior in the nanocomposites. The analysis reveals that important electrical parameters including capacitance (C), dielectric constant (epsilon '), dielectric loss (epsilon ''), loss tangent (tan [[___]]#948;), impedance (Z), electric modulus (M*), phase angle (theta) at related parameters are all significantly influenced by the amount of graphene added to the TPU matrix. Additionally, the study shows that graphene not only improves the microstructure and mechanical strength of TPU composites but also enables control over their electrical and dielectric responses. These findings provide valuable insights for designing flexible and high-performance nanocomposite materials suitable for capacitors, capacitive sensors and energy storage devices.