高阻醇PVDF/超支化聚酰胺共混质子交换膜的制备及性能

Preparation and Properties of High Methanol-Permeation Resistivity PVDF/Hyperbranched Polyamide Hybrid Proton Exchange Membrane

为了制备应用于直接甲醇燃料电池的高阻醇质子交换膜,采用溶液浇铸法,将聚偏氟乙烯(PVDF)与自制的超支化聚酰胺(HBPA)按质量比1∶1,1∶2,1∶3和1∶4制备成共混膜用作质子交换膜,分别编号为PH1-1,PH1-2,PH1-3和PH1-4。在共混过程中,PVDF中的氟基基团(—F)与HBPA中的端羧基基团(—COOH)之间形成了分子间氢键,大量氢键的形成在共混膜中构建出网状交联结构。测试了共混膜的甲醇渗透性能、质子电导率、吸水率和溶胀率、拉伸性能及热稳定性等重要性能。结果表明,构建的网状交联结构有效阻止了甲醇的渗透,使4种共混膜表现出良好的阻醇性能,其中共混膜PH1-1的甲醇渗透率低至5.41×10^(-7)cm^(2)/s,比商用Nafion 117膜低一个数量级,其拉伸强度高达38.24 MPa,是商用Nafion 117的两倍多。PH1-4共混膜的质子电导率最大,80℃时达到2.96×10^(-2)S/cm。采用相对选择性作为衡量质子电导率和甲醇渗透性的综合指标,发现PH1-4在4种膜中表现最佳。由此可见,适当设计和构建网状交联结构能有效提高质子交换膜的阻醇性能,并可对其它性能进行调控。

In order to prepare high-permeation resistivity proton exchange membrane for direct methanol fuel cell(DMFC),PVDF and self-made hyperbranched polyamide(HBPA)were blend at the mass ratio of 1∶1,1:2,1:3 and 1:4 by solution-casting method for preparing hybrid membranes as proton exchange membranes,which were designated as PH1-1,PH1-2,PH1-3 and PH1-4,respectively.In the process of blending,network cross-linked structure in the hybrid membrane was constructed because of the numerous inter-molecular hydrogen bonds between fluoro group(—F)in PVDF and carboxyl end group(—COOH)in HBPA.The methanol permeability,proton conductivity,water uptake,volume swelling,tensile properties and thermal stability of the hybrid membranes were investigated.The results exhibite that the construction of the network cross-linked structure in membrane effectively prevents the permeation of methanol,and the four hybrid membranes show good methanol resistivity.The methanol permeability of the PH1-1 membrane is as low as 5.41×10^(-7) cm^(2)/s,which is one order of magnitude lower than that of commercial Nafion 117 membrane,and the tensile strength of the PH1-1 membrane is up to 38.24 MPa,which is more than 2 times higher than that of the Nafion 117 membrane.The proton conductivity of PH1-4 membrane is the best in four hybrid membranes,which is 2.96×10^(-2) S/cm at 80℃.Relative selectivity is used as a comprehensive indicator to measure proton conductivity and methanol permeability,it is found that PH1-4 exhibits the best relative selectivity of these four hybrid membranes.Therefore,proper design and construction of the network cross-linked structure in proton exchange membrane not only improve effectively the methanol resistivity,but also regulate other properties of proton exchange membrane.