双层同步纺丝法制备PVDF中空纤维微滤膜时温度对膜结构和性能的影响

Effect of tempreture on the structure and properties of PVDF hollow fiber membrane prepared by double-layer synchronous spinning

采用复合热致相分离(c-TIPS)法首次利用三孔喷丝头进行双层同步纺丝,以PEG-200同时作为芯液和外涂层液,制备了内、外表面均开放多孔的聚偏氟乙烯(PVDF)中空纤维微滤膜,并将其应用于直接接触式膜蒸馏(DCMD)中.结果表明,双层同步纺丝法在提高膜机械强度的同时,还能保证较高的膜通量和运行稳定性.主要讨论了芯液和外涂层液温度对膜结构及性能的影响.高温的芯液和外涂层液有利于PVDF结晶,并形成大的球晶,但膜孔径较大,膜容易润湿.适当降低芯液和外涂层液温度,能有效降低膜孔径,当芯液和外涂层液温度分别为60和40℃时,膜通量达33 kg/(m^2·h),且具有较好的运行稳定性,制备的中空纤维膜拉伸强度和膜的断裂伸长率分别达到6.85 MPa和120.2%,可用于膜蒸馏.

In this study, PEG-200 was employed as the bore and outer fluids, polyvinylidene fluoride(PVDF) hollow fibers with open inner and outer surfaces were fabricated via complex thermally induced phase separation(c-TIPS) method. It’s the first time to use double-layer synchronous spinning with triple spinnerent to fabricated PVDF hollow fibers and then tested in direct contact membrane distillation(DCMD). The resules show that mechanical strength improving of the membrane while ensuring high membrane flux and stability via double-layer synchronous spinning method. In double-layer synchronous spinning, PEG-200 was used as both inner bore liquid and outer coating. The effects of inner bore liquid/outer coating temperature on the structure and properties of hollow fiber membranes were discussed. The inner bore liquid and outer coating at high temperature are beneficial to the formation of large spherulites, but the membrane has larger pore size and is easy to wet. The pore size of the membrane can be effectively reduced by properly lowering the temperature of inner bore liquid and outer coating. When the temperature of inner bore liquid and outer coating is 60 and 40 ℃ respectively, the flux of the membrane reaches 33 kg/(m^2·h) and the stability is good. The tensile strength and elongation at break of the prepared hollow fiber membrane are 6.85 MPa and 120.2% respectively, which can be used in membrane distillation.