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以不同结构的聚四氟乙烯(PTFE)平板膜为支撑层、聚二甲基硅氧烷(PDMS)为活性层,通过表面涂覆方法制备PTFE-PDMS复合膜,并用于渗透汽化过程,以实现乙醇-水混合溶液的分离;研究了支撑层结构及制膜参数对其分离性能的影响。结果表明,支撑层结构对复合膜分离因子几乎无影响,对孔径大孔隙率高的支撑层,制膜时,PDMS聚合物向支撑层中渗入过多会使复合膜的渗透通量降低。PDMS聚合物向支撑层渗透形成的过渡层是复合膜传质阻力的重要部分,且过渡层厚,复合膜的耐溶胀性好。综合考虑渗透通量及分离因子,复合膜优化制备条件是交联剂正硅酸乙酯的质量分数4%,交联温度80℃,交联时间为5 h。
Polytetramethylene (PTFE) plate membrane with different structure as supporting layer and polydimethylsiloxane (PDMS) as active layer were prepared by surface coating method and used in pervaporation process. The separation of ethanol-water mixed solution was carried out. The influence of the structure of support layer and membrane-forming parameters on the separation performance was studied. The results show that the structure of the support layer has little effect on the separation factor of the composite membrane. When the PDMS polymer penetrates too much into the support layer during the membrane formation, the permeation flux of the composite membrane decreases. The transition layer formed by the PDMS polymer infiltrating into the support layer is an important part of the mass transfer resistance of the composite film, and the transition layer is thick, and the swelling resistance of the composite film is good. Taking into account the permeate flux and separation factor, the optimized preparation conditions of the composite membrane are as follows: the mass fraction of tetraethyl orthosilicate (crosslinker) is 4%, the crosslinking temperature is 80 ℃ and the crosslinking time is 5 h.