Study on Dielectric Properties of Nanoclay-Modified Disulfide-Containing Polyurea Composites

To address the frequent faults (e.g., bird-related hazards, wind deviation) of transmission lines under extreme environments and the limitations of traditional insulating materials (insufficient dielectric properties, poor interface compatibility, etc.), this study synthesized a disulfide-containing polyurea (DPU) with dynamic covalent bonds and prepared Halloysite nanotubes (HNTs) modified by aminopropyltriethoxysilane (APTES) to form the HNTs/DPU composite. Methods included characterizations like Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and performance tests such as contact angle measurement, breakdown strength, arc resistance, dielectric constant tests, and a tower gap breakdown test. Results showed that APTES modification enhanced interface compatibility, leading to a uniform and dense microstructure. Compared with commercial polyurea (CPU) and commercial insulating sheath (CIS), HNTs/DPU exhibited superior performance: higher glass transition temperature (Tg) and thermal stability, excellent hydrophobicity, improved breakdown strength and dielectric constant, longer arc resistance time by blocking microcrack propagation, and optimal insulation effect at 4 mm coating thickness in the tower gap test with a significantly higher breakdown voltage. In conclusion, HNTs/DPU provides a new technical solution for transmission line insulation protection under extreme conditions, with comparative data demonstrating advancements over existing materials.