Synergistically enhanced dielectric, mechanical, and thermal properties of Ti3C2Tx MXene/millable polyurethane composite films for flexible electronics

The rapid advancement of flexible electronics is driving an urgent demand for polymer-based composites that synergistically possess high dielectric performance and superior mechanical properties. This study presents Ti 3 C 2 T x MXene/millable polyurethane (MPU) composite films fabricated via a combined mixing and hot-pressing approach, with a systematic investigation into the effects of MXene content on their properties. The dielectric constant increased linearly with filler content, attaining a value of 11.71 at 1 kHz for the composite with 12 wt% filler. An optimal balance was achieved at 8 wt% loading, yielding a dielectric constant of 11.13 (a 17.3 % enhancement over the neat MPU matrix value of 9.49) coupled with a low dielectric loss of 0.037. The breakdown strength peaked at 69.5 kV/mm for the 6 wt% composite (a 21.5 % improvement) and remained high at 60.2 kV/mm for the 8 wt% composite (a 5.2 % increase). Mechanical properties were significantly enhanced, with the elongation at break reaching a maximum of 682.7 % (94.8 % increase) and 614.1 % (75.3 % increase) at 10 wt% and 8 wt% loadings, respectively. Thermal stability was also enhanced, as evidenced by a 14.4 °C increase in the temperature for 5 % weight loss (to 276.1 °C) for the 10 wt% composite. Microstructural analysis revealed that the uniform dispersion of MXene enhanced interfacial polarization, the hot-pressing-induced orientation of lamellar planes elongated the electrical tree path, and a hydrogen-bonding network formed between the surface functional groups (–O, –OH) of MXene and MPU synergistically improved interfacial stress transfer and thermal stability. This work demonstrates the synergistic optimization of electrical, mechanical, and thermal properties via gradient filler content control, offering a novel strategy for designing high-performance flexible electronic materials.