Study On Melt-spinning Polyurethane Based Hollow Fiber Membrane

Based on the principle of polymer blend phase separation and the way of washing-out additive to form the micro-voids,PEG as additive,PU/PVDF hollow fiber membrane was produced with the method of melt-spinning.And base on that, adding diluent,the PU/CaCO₃ hollow fiber membrane was produced in low spinning temperature.The compatibility of the polymer was discussed,then choose the disperse phase; analyzed the content of the disperse phase work on interfacial micro-voids and the spinning;researched the drawing and PEG impact on the configuration of the PU/PVDF hollow fiber membrane.Further probe into reduced the spinning temperature by diluent,discussed the affection of the cooling temperature,finalize the design by heat,and the molecular weight of additive to the structure and performance of the PU/CaCO₃ hollow fiber membrane.First,the microstructure of membrane was observed,the results showed that: because of the bad compatibility between PU and PVDF,the interfacial micro-voids were formed by drawing,and after washing out the PEG,the non-interfacial micro-voids were formed,also it can increased the size of interfacial micro-voids.The PU/PVDF hollow fiber membrane possessed interfacial and non-interracial micro-voids.To the PU/CaCO₃ hollow fiber membrane,twenty thousand molecular weight of additive was good to form more penetrated micro-voids than fifty thousand molecular weight,and the content of additive increased,on the surface of membrane the number and size of micro-voids increased.Also,the properties of the hollow fiber membrane were also studied.By testing the porosity rate,the flux and retention,and so on,the results showed that because of its non-penetrated micro-voids,non-drawing PU/PVDF hollow fiber membrane did not have flux,after drawing of membrane,the flux and porosity rate increased,but not increased straightly.The flux of non-drawing PU/CaCO₃ hollow fiber membrane was small,and increased straightly when the drawing increased,after finalized the design of membrane by heat,the flux reach to 200L/m².h and declined slowly.Further,the PU hollow fiber membrane produced by melt-spinning,its break force higher than which was produced DIPS,and its initial module lowness,its break elongation rate can reach to 800%,so the membrane was sensitivity to pressure, following the pressure increased or decreased,the structure,flux and retention of membrane responded to the pressure.Compared with PU/PVDF hollow fiber membrane,PU/CaCO₃ hollow fiber membrane possessed better pressure-response, and increasing the drawing,the membrane exhibited pressure-response well, extending the working time,the pressure-response of membranes tended to stably.