The application of conventional polyimide in the insulation structure of rail transit traction motors is prone to corona breakdown failure, which seriously affects the reliability and safety of the motor's long-term operation. In this paper, three corona-resistant polyimide materials were prepared by using 4,4′-diaminodiphenyl ether (ODA) as the diamine, pyromellitic dianhydride (PMDA) as the dianhydride, and nano-alumina surface treated with different silane coupling agents as the inorganic filler. The impact of various coupling agents on their surface morphology, mechanical properties, corona-resistant lifetime, and electrical breakdown performance were investigated. The results show that the surface treatment with silane coupling agents can improve the dispersibility of alumina in the polyimide matrix, reduce the agglomeration of nano-alumina, and enhance the corona-resistant properties of the polyimide material, while its excellent mechanical properties are maintained. Among them, the dispersion stability of nano-alumina surface treated with bis-amino silane coupling agent is the best, and the prepared corona-resistant polyimide material also has the best surface morphology and comprehensive performance. The corona-resistant time is 25 min and 120 min, respectively under 3 kV and 2 kV, the tensile strength reaches 167 MPa, and the elongation at break is 29.5%.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |