复合增强三孔中空纤维膜的制备

发布时间：2018-04-14 22:46

  本文选题：熔融纺丝法 + 非溶剂致相分离法　； 参考：《天津工业大学》2017年硕士论文

【摘要】：中空纤维膜因其较多的优点广泛应用于超微滤、膜蒸馏等过程中。但在规模化应用过程中发现,膜强度是影响膜系统稳定运行的主要问题。中空纤维膜在气流和水流的冲击下容易出现断丝的现象,膜组件使用寿命缩短,因此开发高强度的中空纤维膜具有很大的应用价值。为此,本文首先研究了熔融纺丝工艺与纤维结构和性能的关系,得到了高拉伸断裂强度PVDF纤维;其次将PVDF纤维与三孔中空纤维进行复合,制备高拉伸断裂强度的复合增强中空纤维膜。为得到高拉伸强度的聚偏氟乙烯(PVDF)纤维,通过正交实验和单因素实验,研究了熔融纺丝法制备PVDF纤维的工艺条件,并利用热分析(DSC)、红外光谱法(FTIR)、X-射线衍射(XRD)和拉伸实验研究了纤维的晶体结构、晶区取向和力学性能。研究结果表明,纺丝过程中影响纤维拉伸强度的因素主次顺序为:卷绕速率喷头温度入水距离;纤维拉伸强度随着冷拉伸倍数的增大而提高。利用熔纺PVDF纤维拉伸过程中产生的残余应力对其进行定长后处理,并对后处理过程中的最优工艺条件进行探索,从而得到拉伸强度优异的聚偏氟乙烯(PVDF)纤维。利用红外光谱(FTIR)、X-射线衍射(XRD)、差示扫描量热(DSC)分析了纤维的晶体结构、晶区取向和力学性能。研究结果表明,在残余应力作用下的后处理过程中纤维进一步发生了 α晶型向β晶型的转变,结晶度和晶区取向均有所提高,断裂强度提高明显,PVDF纤维在60 ℃的水浴下处理3小时可使断裂强度达到633 MPa,相比未处理前提高了 70 MPa。在三孔PVDF中空纤维膜的纺制工艺的基础上,通过对喷丝头的改造,将高拉伸断裂强度的聚偏氟乙烯(PVDF)熔纺纤维与三孔中空纤维膜进行复合,从而利用纤维的力学增强作用制备出高拉伸断裂强力的复合三孔中空纤维膜。通过对复合膜的超滤水通量、最大孔径、破裂压力、膜蒸馏通量等一系列基本性能测试,证明PVDF熔纺纤维在增强膜拉伸断裂强力的同时并未对膜的其他性能造成影响。
[Abstract]:Hollow fiber membrane is widely used in ultrafiltration and membrane distillation because of its advantages.However, in the process of large-scale application, it is found that the membrane strength is the main problem affecting the stable operation of the membrane system.The hollow fiber membrane is easy to break under the impact of air flow and water flow, and the service life of the membrane module is shortened. Therefore, the development of high strength hollow fiber membrane has great application value.Therefore, the relationship between the melt spinning process and the structure and properties of the fibers was studied, and the high tensile breaking strength PVDF fiber was obtained, and the PVDF fiber was combined with the three-pore hollow fiber.Composite reinforced hollow fiber membranes with high tensile fracture strength were prepared.In order to obtain high tensile strength polyvinylidene fluoride (PVDF) fiber, the technological conditions of preparing PVDF fiber by melt spinning method were studied by orthogonal experiment and single factor experiment.The crystal structure, crystal orientation and mechanical properties of the fiber were studied by thermal analysis, FTIR and X-ray diffraction (XRD) and tensile tests.The results show that the main and secondary factors affecting the tensile strength of the fiber during spinning are as follows: winding rate nozzle temperature inlet water distance, and the fiber tensile strength increases with the increase of cold drawing ratio.The polyvinylidene fluoride polyvinylidene fluoride (PVDF) fiber with excellent tensile strength was obtained by using the residual stress produced in the tensile process of melt-spun PVDF fiber to carry out the fixed length post-treatment and to explore the optimum process conditions in the post-treatment process.The crystal structure, crystal orientation and mechanical properties of the fiber were analyzed by FTIR X-ray diffraction (XRD) and differential scanning calorimetry (DSCS).The results show that during the post-treatment under residual stress, the transformation of 伪 -crystalline form to 尾 -crystalline form occurs further, and the crystallinity and orientation of the crystal zone are improved.The fracture strength of PVDF fiber increased obviously when treated in water bath at 60 鈩，

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