聚酰亚胺/聚丙烯腈共混黑膜的制备及其结构与性能

Preparation of Polyimide/Polyacrylonitrile Blend Black Films and Study of Their Structure and Properties

采用共混的方法制备聚酰胺酸/聚丙烯腈(PAA/PAN)共混溶液.其中2种PAA溶液分别由二酐(3,3′,4,4′-联苯二酐(BPDA)与均苯四甲酸二酐(PMDA))和二胺(对苯二胺(PDA)与4,4′-二氨基二苯醚(ODA))均聚或共聚而得,N,N-二甲基乙酰胺(DMAc)为溶剂,PAN溶于DMAc中制成溶液后与PAA溶液混合,涂膜后热处理制得聚酰亚胺(PI)/PAN共混薄膜.分析了PAA和PAN在热处理过程中的变化,以及PAN的加入量对共混薄膜的结构与性能的影响.结果表明,在热处理过程中,PAA完成了亚胺化成为PI,而PAN完成了预氧化,形成了稳定的梯形结构,制备出具有良好力学性能、黑色、不透光的薄膜,但是随着PAN含量的增加,体系发生明显的相分离,薄膜力学性能有所下降,(BPDA/PDA/ODA)PI中加入10%的PAN和(PMDA/ODA)PI中加入20%的PAN时能获得具有良好力学性能的黑色、低透光率的薄膜.

Black films play an important role in optics, electronics and other high-tech areas. This study aimed to produce a type of blend film that exhibits excellent mechanical properties and low transmittance. Blends of solutions were prepared by mechanical mixing a solution of poly（amic acid） （PAA） with that of polyacrylonitrile （PAN）. Two types of PAA were synthesized, from BPDA/PDA/ODA and PMDA/ODA. The black films of PI/PAN were obtained by casting the solution blend onto a glass and followed by a thermal treatment. The blend films were withdrawn from the oven set at different temperatures. From these blend films, it was clearly observed that the color of the blend films changed from yellow to black. The effect of PAN content on their properties, structure and phase separation between PI and PAN were studied in detail. The blend films were characterized by Fourier transform infrared spectrometry, X-ray diffraction and universal materials tester. The results showed that imide rings were successfully formed and that the preoxidation of PAN was essentially complete. The mechanical strength decreased with increased PAN content, which was supported by the results from scanning electron microscopy （SEM） and UV-Vis light detector. The blend films were treated with a potassium hydroxide solution for 15 min. It was found that phase separation occurred between PI and PAN, revealed by observation of the surface and the cross-section morphology by SEM. With the increase in PAN content, the degree of phase separation also increased, which resulted in lower mechanical strength. This conclusion was also confirmed by the results of UV-Vis light detector. The transmittance of the blend films reduced because of the phase separation. In summary, the blend films of （BPDA/PDA/ODA）PI containing 10 wt% PAN and those of （PMDA/ODA）PI containing 20 wt% PAN exhibited excellent mechanical properties and low transmittance.