| Polyvinylidene fluoride(PVDF)hollow fiber membrane was widely used in ultrafiltration,membrane distillation of membrane separation technology due to its excellent properties.But the hollow fiber membrane was broken esaily under the impact of water flow or airflow and strong disturbance of operating environment,and shortened useful life of the membrane module and greatly limited the wide application of hollow fiber membrane,therefore it was significant to develop high-strength hollow fiber membranes.A composite membrane structure and the new preparation were designed in the article.A outside-inside membrane having a high tensile strength by using a self-designed spinning spinneret with a special structure was prepared.Compared with the circular outer pressure membrane,the blossom geometry membrane had a larger outer surface area,which could improve the penetration efficiency of the hollow fiber membrane.Firstly,it was discussed the effect of spinning nozzle parameters on morphology and properties of composite membrane,such as needle type,center distance of the spinneret orifice,needle position and needle length.And through the test of pure water flux,anti-crushing ability,maximum pore size and maximum load,it was obtained the preparation parameters of the optimal performance of the composite membrane:it was used the spinning parameter of a spinnerent of vertical needle,a center distance of the nozzle bore of 4 mm,a needle position ratio of 1:2,and a needle excending length of 5 mm,and prepared the composite menmbrane with PVDF fiber in the middle of three boers and uniform film thickness.The membrane crushing resistance and the bursting pressure are optimized without affecting the membrane permeability.Based on the optimal parameters of the spinneret,it was discussed the effects of spinning parameters on the properties of the composite membrane,such as water inlet distance and winding speed of the spinning process.The experimental results show that it xwas the optimal performance when the water inlet distance was 11 cm,the winding speed was 20.7m/min,the prepared composite membrane had a pure water flux of 245 L·m-2·h-1,a crushing resistance of 0.230 MPa,a maximum pore diameter of 0.160?m,and a bursting pressure of 0.385 MPa.Then,it was discussed the effects of different film wall thickness on the composite membrane based on the basis of the optimal spinning process.It was found that when the film wall thickness was increased,the pure water flux was decreased and the crush resistance and fracture pressure was increased of the composite membrane.The smaller the thickness of the membrane wall could improve membrane mass transfer efficiency,but the composite membrane was difficult to form.Therefore,the composite membrane with a membrane wall thickness of 230?m had the best permeability and mechanical strength under the premise of ensuring the stability of the composite membrane molding process.Finally,it was compared the three types of hollow fiber membranes of single-bore,three-bore and fiber reinf'orced by the basic properties such as pure water flux,maximum pore size,fracture pressure and fracture strength.The results was showed that compared with single-bore and three-bore membrane,the fiber-reinforced PVDF membrane hacd a slight decrease in pure xwater flux and a minor changes in maximum pore size and brust pressure of the membrane,but the breaking stren."gth of the composite membrane was about 12 times higher than that of the single-bore membrane,reaching 23.64N.Therefore,the breaking strength of the composite membranes was significantly improved by adding PVDF fibers without affecting permeability of the membranes. |
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