可交联聚酰亚胺膜的制备及其气体分离性能研究

发布时间：2018-03-19 23:00

  本文选题：聚酰亚胺　切入点：碳纳米管　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：如何将CO_2从其他混合气体中有效的分离出来,是化工和环境等领域中的重要分离过程。与传统的分离过程(如吸收、吸附)相比,膜的CO_2吸收过程具有高效率、低成本、低耗能、高灵活性等优点[102-103]。聚酰亚胺不但具有优异的综合性能,还兼具较强的气体选择性。但是,由于聚酰亚胺主链上含有刚性较大的芳环结构,且链间存在较强的分子间作用力,导致其自由体积比较小,并且其在高压下易塑化的缺点,使气体分离性能下降的同时也增加了运作成本,这些都极大的限制了聚酰亚胺膜材料在气体分离膜领域的广泛应用。交联是解决聚酰亚胺塑化问题和提高膜气体分离性能的新兴改性方法,交联网络的形成可以适当地降低分子链段的运动能力,提高气体选择性,并且交联改性通常会增加聚酰亚胺抗塑化性能,使聚酰亚胺在高压冷凝性气体或苛刻操作环境中分离时具有更好性能。填加无机粒子的混合基质膜是改性高分子材料近几年来的研究热点,碳管纳米级别的管径和光滑孔道结构为气体分子的扩散提供尺寸可控的良好通道,成为提高膜气体分离性能理想的纳米无机填料。本论文从聚酰亚胺分子结构的设计出发,引入大自由体积三氟甲基,引用光引发剂实现聚合物光交联,填加多壁碳纳米管制成混合基质膜。首先,设计合成了含烯丙基二胺单体3,3′-二烯丙基-4,4′-二(4-氨基-2-三氟甲基苯氧基)联苯(DBDA),并利用DBDA与4,4'-二氨基二苯醚(ODA)和六氟二酐(6FDA)合成聚合物,并对其进行了红外、核磁和质谱等结构表征,结果表明合成得到了设计的目标产物。聚合物玻璃化转变温度随着烯丙基含量的增加而下降。且随着温度的升高出现第二个损耗角正切峰,表明烯丙基发生交联反应。合成聚酰亚胺有优异的热稳定性,机械性能。将引发剂加入聚合物中,采用紫外辐照法促使聚合物交联。光交联后FTIR谱图中1678 cm-1处的碳碳双键红外吸收峰消失;DMA测试表明,交联聚合物Tg均升高,增加幅度约4-9℃,且第二个损耗角正切峰强度降低,证明交联反应的发生。交联后聚合物热稳定性和机械性能均有所提高。选取50%PI填加1wt%MWCNT制备混合基质膜CNT50%PI和交联混合基质膜C-CNT50%PI。因为碳管的加入降低了链段运动能力,聚合物50%PI填加碳管后Td5%和Tg均提高;CNT50%PI经过交联处理后,Tg和Td5%进一步升高,以上结果是由于交联后形成的三维网络结构限制聚合物分子链运动,提高聚合物Tg和热稳定性。光交联形成的三维网络结构使CO_2和N_2的渗透系数减小,但CO_2/N_2的选择系数提高;MWCNTs拥有纳米级别的管径和光滑孔道结构为气体分子的扩散提供尺寸可控的良好通道,50%PI填加1wt%MWCNTs后,其对CO_2和N_2的渗透系数分别提高42%和52%,且CO_2/N_2选择系数几乎不变,从而提高工业操作效率。
[Abstract]:How to effectively separate CO_2 from other mixed gases is an important separation process in the fields of chemical industry and environment. Compared with the traditional separation process (such as absorption, adsorption), the CO_2 absorption process of the membrane has high efficiency and low cost. The advantages of low energy consumption and high flexibility [102-103]. Polyimide not only has excellent comprehensive properties, but also has strong gas selectivity. However, because of the rigid aromatic ring structure in the main chain of polyimide, The existence of strong intermolecular force between chains leads to a small free volume, and it is easy to be plasticized at high pressure, which decreases the gas separation performance and increases the operating cost. These have greatly limited the wide application of polyimide membrane materials in the field of gas separation membrane. Crosslinking is a new modification method to solve the problem of polyimide plasticization and improve the gas separation performance of the membrane. The formation of crosslinking network can reduce the mobility of molecular segment, improve gas selectivity, and the crosslinking modification usually increases the plasticization resistance of polyimide. The polyimide has better performance when it is separated in high pressure condensable gas or harsh operating environment. The mixed matrix film filled with inorganic particles is the research hotspot of modified polymer materials in recent years. The diameter and smooth pore structure of carbon nanotubes provide a good channel with controllable size for the diffusion of gas molecules and become the ideal nano-inorganic fillers for improving the gas separation performance of the membrane. In this paper, the molecular structure of polyimide is designed. Introducing large free volume trifluoromethyl, using photoinitiator to realize photocrosslinking of polymer, adding multi-wall carbon nanotubes to prepare mixed matrix membrane. A monomer containing allylenediamine, 3Amino-diallyl-4Amino-difluoro-2-trifluoromethylphenoxy), was designed and synthesized. The polymers were synthesized by using DBDA and 4 ~ (4) -diaminodiphenyl ether (ODAA) and hexafluorodianhydride (6) FDAs, and their infrared spectra were studied. The results of NMR and MS showed that the target product was obtained. The glass transition temperature of polymer decreased with the increase of allyl content, and the second tangent peak of loss angle appeared with the increase of temperature. The results show that the crosslinking reaction of allyl group takes place, the synthesis of polyimide has excellent thermal stability and mechanical properties, and the initiator is added to the polymer, The UV irradiation method was used to promote the crosslinking of polymers. The results of UV-DMA measurements of infrared absorption peaks of carbon and carbon double bonds at 1678 cm-1 showed that TG of the crosslinked polymers increased by about 4-9 鈩，

本文编号：1636378