In order to study the reliability of nitrile butadiene rubber (NBR) sealing element under the action of extremely low temperature and oil medium, the mechanical properties and microstructure of sealing rings in high-voltage transformers in extremely cold regions were studied. The mechanical characteristics, morphology change, chemical structure characteristics, and thermal response characteristics of the sealing ring after serviced for one year in extremely cold environment were obtained by tensile test, micron indentation test, scanning electron microscope (SEM), infrared spectrum (FTIR), and differential scanning thermal analysis (DSC). The results show that the elastic modulus and hardness of NBR sealing ring decrease in extremely cold environment, which leads to the loss of sealing effect. This is because the surface of sealing ring swell under the joint action of low temperature and oil medium, and micro-cracks appear. Oil immersion in NBR makes the molecular chain spacing increase, and the compliance of main chain of NBR is improved, meanwhile, the molecular structure of NBR changes due to the hydrolysis reaction of cyanide group.
| 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 |