高性能聚酰亚胺氧气/氮气分离膜的设计与制备

Design and synthesis of high performance O_(2)/N_(2) separation membranes based on novel polyimide

以9,9-双(4-氨苯基)芴(FDA)、4,4′-(六氟异亚丙基)二邻苯二甲酸酐(6FDA)和均苯四甲酸酐(PMDA)为单体采用高温一步法制备了一种三元聚酰亚胺6FDA/PMDA-FDA.通过核磁和红外光谱验证了产物的结构.该聚酰亚胺具有良好的溶解性和热稳定性.通过使用非溶剂诱导相分离(NIPS)法控制相转化时间来调控不对称膜的活性层厚度,然后再在该膜表面涂覆聚二甲基硅氧烷(PDMS)涂层来制备复合膜.通过扫描电镜确定了活性层厚度,用EDS测试了PDMS涂层的厚度和分布.分别测试了聚酰亚胺基膜、各向异性膜和复合膜的氧气/氮气分离性能,结果表明,在30 s相转化时间得到的M3拥有最佳的气体渗透性,其氧气的通量达到了25 GPU,氧气/氮气选择性达到5.4,其复合膜的氧气通量达到17.8 GPU,氧气/氮气选择性达到7.0,在膜法富氧方面显示出应用前景.

A novel polyimide was synthesized from 9,9′-fluorene-4,4′-diamine,pyromellitic dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride by a one-pot high temperature method.The resulting polyimide(6 FDA/PMDA-FDA)was confirmed by ^(1)HNMR and FTIR.This PI showed good solubility,and thermal stability.The anisotropic membrane was obtained by non-solvent induced phase separation(NIPS)method,and the thickness of the skin layer was controlled by the evaporation time of the casting solvent before dip into water.The anisotropic membrane was thereafter coated with a thin layer of PDMS,the thickness of the active layer,composite layer and the distribution of the silicon were analyzed by SEM/EDX.The resulting membrane of M3 exhibited an O_(2) flux of 25 GPU and O_(2)/N_(2) selectivity of 5.4.Additionally,the flux of O_(2) for C3 is 17.8 GPU and the O_(2)/N_(2) selectivity reaches as much as 7,indicating a good potential for O_(2) enrichment from air.