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Polyimide films with high porosity were prepared using 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diamino-2,2′-dimethyl-biphenyl (mTB) as monomers. During the preparation process, pore-forming agent was added into the system, and the high-temperature thermal imidization of polyamide acid was controlled by the principle of thermo-induced phase separation. The micropore morphology, mechanical properties, and dielectric properties of the films were analyzed. The results show that the porosity of porous films reach 50%-60%. Under the frequency of 10 GHz, the dielectric constant and the dielectric loss factor of the sample PI-1-250-4 h is 2.14 and 0.002 8, respectively, while maintaining good mechanical properties and heat resistance. Due to the introduction of rigid biphenyl building blocks, the porous film still maintains a low coefficient of thermal expansion. The adhesive-free double-sided copper clad laminate, which prepared by combining the porous film with thermoplastic polyimide (TPI) and then pressing copper foil at high temperature, has good interface adhesion and solder resistance, and can apply to high-frequency and high-speed flexible copper clad laminates.
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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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