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采用两步法制备了均苯型纯聚酰亚胺(polyimide,PI)薄膜,并对该薄膜、3M和杜邦公司生产的纯PI薄膜进行热激电流测试。结果表明:3M纯PI的γ峰对应峰温和陷阱能级相对较高,这可能是其较高的聚合度,导致分子链的运动困难造成的,自制纯PI过程中适当提高聚酰胺酸粘度,有利于提高聚合度进而改善其性能;3M和杜邦纯PI薄膜β峰对应峰温比自制PI的峰温高35 K,这也是3M和杜邦纯PI的聚合度高,导致侧基运动困难造成的。β峰与偶极取向松弛有关,非晶PI的β峰峰温大约为345 K,比玻璃化转变温度略小,此温度下大分子链迁移困难,只有如羰基等极性基团的迁移。另外,只有杜邦纯PI有αC峰,这与薄膜内的晶区或界面效应有关。
Pure polyimide (PI) films were prepared by a two-step process. The thin films, 3M and DuPont pure PI films were tested for the thermal shock current. The results showed that the peak temperature and the trap level of the γ peak of 3M pure PI were relatively high, which may be due to its high degree of polymerization, resulting in the difficulty of movement of the molecular chain. The polyamic acid viscosity, Which is conducive to increasing the degree of polymerization and thus improving its performance. The peak temperature corresponding to β peak of 3M and DuPont pure PI film is 35 K higher than the peak temperature of self-made PI, which is also caused by the high degree of polymerization of 3M and DuPont pure PI, . The β peak is related to the relaxation of the dipole orientation. The peak temperature of β peak of amorphous PI is about 345 K, which is slightly smaller than the glass transition temperature. The migration of macromolecular chains is difficult at this temperature, and only polar groups such as carbonyl groups migrate. In addition, only DuPont pure PI has an aC peak, which is related to grain boundaries or interfacial effects within the film.