聚全氟乙丙烯中空纤维膜制备及其膜蒸馏过程*

以聚全氟乙丙烯(FEP)为成膜聚合物, 采用熔融纺丝-拉伸法制备FEP中空纤维膜, 研究了后拉伸倍数对FEP中空纤维膜结构与性能的影响。结果表明, 初生FEP中空纤维膜结构较为致密, 拉伸后出现微孔结构。随着拉伸倍数的提高膜的孔隙率和氮气通量明显增大, 而液体渗透压(LEP)有所降低。将所得FEP中空纤维膜用于减压膜蒸馏(VMD)研究, 并将其与常规熔融纺丝-拉伸法聚丙烯(PP)中空纤维膜比较。结果表明, 所得FEP中空纤维膜的疏水性能、液体渗透压力和力学强度均优于PP中空纤维膜。较强的疏水性能使其稳定运行而不被液体渗透, 脱盐率稳定在99%以上。同时, FEP中空纤维膜具有较大的内径(0.74 mm), 在保证较高脱盐率前提下可采用内压式减压膜蒸馏, 且真空膜蒸馏通量随着进料温度的升高显著增高。

FEP Hollow Fiber Membrane and Its Membrane Distillation Process

The influence of draw ratio on the structure and properties of poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) hollow fiber membrane which was fabricated by melt-spinning stretching (M-S) method was investigated in this article. The primary FEP hollow fiber membrane structure was compact while the porous structure occurs after stretching. Furthermore, the increase of membrane draw ratios induced the obvious increase of membrane porosity and the N₂ flux while the decrease of the liquid entrance pressure (LEP). Meanwhile, the FEP hollow fiber membrane was applied to the vacuum membrane distillation (VMD) process to compared with M-S PP hollow fiber membrane which was the commercial product. The results show that the hydrophobic properties, LEP and mechanical strength of FEP hollow fiber membrane was better than PP hollow fiber membrane. The strong and stable of hydrophobic properties enabled the FEP membrane unpenetrated, which kept the desalination rate maintain up to 99%. The larger inner diameter (about 0.74 mm) of FEP hollow fiber membrane induced the use of internal pressure VMD type which brought about the higher VMD flux when the feed temperature increased.