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Drawing technology is one of the important methods for preparing electronic-grade polyimide (PI) films used in flexible printed circuits (FPC). Compared to single chemical structure regulation methods, drawing technology offers higher flexibility and can effectively regulate the coefficient of thermal expansion (CTE) of different systems of PI films over a wide range. However, in the pursuit of high glass transition temperature (Tg), monomers with rigid property and hydrogen bond are often partially or fully employed, leading to reduced molecular chain mobility and impairing the drawing processability. This paper addressed the challenging contradiction between the high glass transition temperature (Tg) of polyimide (PI) films and their drawing processability. Taking pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA) as basic system, a series of homopolymer and copolymer PI films were designed and prepared by introducing p-phenylenediamine (p-PDA), 2,5-dimethy-phenylenediamine (DPD), and m-phenylenediamine (m-PDA). Through molecular simulation and experimental analysis, the effects of the main chain structure on its segment mobility and drawing process were studied systematically. The results show that the introduction of m-PDA can simultaneously improve the rigidity of PI molecular chains in the PMDA/ODA system below Tg and the mobility above Tg, thereby enabling it to have a high Tg and excellent drawing processability. By employing DMA for high-temperature drawing and orientation of this system film, PI film samples with high Tg (about 428℃) and CTE-adjustable (1.7×10-6-34.1×10-6℃-1) were successfully prepared.
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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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