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Epoxy composite insulating materials doped with 0%, 1%, and 10% of modified nano Al2O3 were prepared and conducted thermal ageing tests at 150℃, and their thermal ageing characteristics and mechanism were studied through dynamic thermal mechanical testing, scanning electron microscopy testing, and linear thermal expansion testing. The results show that an inhomogeneous ageing structure is formed in epoxy composite insulating material during thermal ageing, and the thickness of surface ageing layer is related to the content of nano Al2O3. When the doping mass fraction of nano Al2O3 is 1%, the thickness of surface ageing layer is the smallest, and the nanoparticles are well dispersed and closely embedded in the epoxy matrix. According to the free volume theory of glass transition, it is found that the free volume fraction of sample is the smallest when the doping mass fraction is 1%, the corresponding α main relaxation time of the epoxy matrix is the longest, and the molecular chain activity is the lowest. Adding an appropriate amount of modified nano Al2O3 into the epoxy resin can improve the cross-linking degree of molecular chain and reduce the free volume of system. Thereby the diffusion of oxygen in the material is weakened, and finally the inhomogeneous thermal ageing degree of the epoxy composite insulating material is reduced.
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| 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 |
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