In this paper, the effects of properties of chopped fiber on the breakdown strength, conductivity, trap characteristics, and mechanical properties of meta-aramid paper were studied. The results show that based on the reference sample of which the fiber diameter is 25 μm, fiber length is 6 mm, crystallization temperature is 300℃, and the ratio of precipitated fibrids and chopped fibers is 7:3, when the fiber diameter increases to 45 μm, the embedding degree of chopped fibers decreases, interface pores appear, and the breakdown and tensile strength of aramid paper can decrease by 16% and 24%, respectively. When the length of fiber increases to 18 mm, chopped fiber morphology shows coiling-type thus forming the "hard-form" interface, the breakdown strength of aramid paper decreases by 63%, while the tensile strength shows little change. When the crystallization temperature decreases to 230℃, the structural stability of chopped fibers reduces, which causes their melting under hot-pressing process, and the breakdown strength and tensile strength decreases by 36% and 50%, respectively. With the increase of proportion of chopped fiber, the breakdown strength of aramid paper increases at first and then decreases, which is along with the change of paper compactness, while the tensile strength of aramid paper increases monotonically with the increase of chopped fiber content, which reflects the necessity of chopped fibers for the stable molding of aramid paper and the weakening effect of excessive chopped fibers on electrical insulation. In addition, the aramid papers with low breakdown strength show a higher conductivity and a shallower trap depth, which can be regarded as reference indexes for the insulation performance of meta-aramid papers.
| 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 |