Abstract: With the insulation faults caused by bird damage, foreign object short circuits and extreme weather in transmission lines showing an increasing trend year by year, improving the insulation strength of the gap between transmission towers has become an urgent problem to be solved. This paper aims at the problems of insufficient performance of traditional insulating sheaths and difficult insulation protection on the ground potential side. Using bis-(4-hydroxyphenyl) disulfide as a chain extender and by regulating the molecular weight ratio of polypropylene glycol bis(2-aminopropyl ether), polyurea materials with dynamic disulfide bonds are synthesized. The chemical structure, microstructure, hydrophobicity, chemical resistance, thermal properties and breakdown strength of the material were studied byinfrared spectroscopy(FT-IR), contact angle measurement, SEM and differential scanning calorimetry. The results show that an increase in the content of PPG-2000 can significantly improve the hydrophobicity of the material(with a maximum contact angle of 97.1°) and reduce the water absorption rate(as low as 3.32%). In addition, the breakdown strength is 20.03 kV/mm when the molar ratio is 1.5∶0.5. Further gap simulation tests show that a 4.5 mm thick coating can increase the breakdown voltage of the tower gap by 4.8%. This research provides a new type of polyurea material design and experimental basis for insulation strengthening on the ground potential side of transmission lines, which has important engineering application value.

Key words: transmission tower gap, polyurea, disulfide bond, contact angle, water absorption rate, breakdown strength