Abstract

The aim was to prepare copolyimide (BPDA/PMDA-PDA) films of low thermal expansion coefficient by incorporating 1,2,4,5-benzenetetracarboxylic anhydride (PMDA) into polymer backbones 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)/p-phenylenediamine (PDA). FTIR and WAXD were used to explore the chemical and physical microstructure of the PIs films. DMA, TMA and TGA were used to characterize the mechanical and thermal performance of the PIs film respectively. The results show that the smectic structure of the film was destroyed by introducing rigid PMDA groups. The free volume fraction of polymers reached its maximum value when 40 wt % PMDA was added. The glass transition temperature of the polymers increased from 330 to 430°C and the thermal decomposition temperature declined slightly with the addition of PMDA. The inflection point in thermal expansion coefficient (CTE) of the BPDA-PDA polymers in TMA test reached as high as 470°C. The glass transition temperature of the polymers increased but the service temperature range narrowed with the addition of PMDA. The optimized PMDA concentration to obtain a best CTE was 5% as was revealed by the experimental results. The insights obtained from the experiments indicated that excessive introduction of PMDA into the polymers could increase the glass transition temperature significantly. However, the operating temperature range may be reduced. This research could offer practical and valuable references to the application for co-PI films.

中文翻译：

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1,2,4,5-苯四甲酸酐与3,3',4,4'-联苯四甲酸二酐/对苯二胺复合制备的Co-PI薄膜的结构-性能关系

摘要

目的是通过将 1,2,4,5-苯四甲酸酐 (PMDA) 掺入聚合物主链 3,3',4,4'-联苯四甲酸二酐 (双酚A)/ p-苯二胺 (PDA)。FTIR 和 WAXD 用于探索 PIs 薄膜的化学和物理微观结构。DMA、TMA和TGA分别用于表征PIs薄膜的机械和热性能。结果表明，刚性PMDA基团的引入破坏了薄膜的近晶结构。当添加 40 wt% PMDA 时，聚合物的自由体积分数达到最大值。随着 PMDA 的加入，聚合物的玻璃化转变温度从 330 摄氏度上升到 430 摄氏度，热分解温度略有下降。BPDA-PDA聚合物在TMA测试中的热膨胀系数（CTE）拐点高达470℃。随着 PMDA 的加入，聚合物的玻璃化转变温度升高，但使用温度范围变窄。如实验结果所示，获得最佳 CTE 的优化 PMDA 浓度为 5%。从实验中获得的见解表明，向聚合物中过量引入 PMDA 会显着提高玻璃化转变温度。但是，工作温度范围可能会降低。该研究可为co-PI薄膜的应用提供实用且有价值的参考。