静电直写聚偏氟乙烯纤维膜结构设计及应用

Structure Design and Application of Polyvinylidene Fluoride Fibrous Membrane by Electrostatic Direct-Writing

以聚偏氟乙烯(PVDF)为成膜聚合物,N,N-二甲基乙酰胺(DMAc)/丙酮为混合溶剂制得纺丝液,采用静电直写技术制备了具有规整孔结构的PVDF多孔纤维膜。通过AutoCAD设计了不同膜孔间距的孔形貌,研究了溶剂组成对PVDF纺丝液流变性能和纺丝成纤性能的影响。结果表明,挥发性丙酮的加入有效地降低了纺丝液黏度,同时也提高了PVDF纤维膜的固化速率,有利于静电直写纤维膜的固化成形。此外,当电场电压3.5 kV、接收距离10 mm、挤出速率0.25 mL/h,直写5层时,所得PVDF纤维膜具有较好的规则孔形状和球晶次级结构。通过扫描电镜、静态水接触角、力学性能、渗透通量等测试分析,当设置孔间距为0.3 mm,所得PVDF纤维膜静态水接触角为117°,用于油水分离通量达1111.08 L/(m^2·h)(高10 cm油水自身质量),分离效率高于98%。

Polyvinylidene fluoride(PVDF)porous flat-sheet membranes with regular pore structure were fabricated by direct-writing technique.Especially,the spinning solution was prepared by using PVDF as membrane material,and DMAc/acetone as mixed solvent.Pore structure with different geometric parameters(pore shape and pore size)was designed by AutoCAD.Effects of solvent composition on rheological properties and spinnability of PVDF spinning solution were investigated.Results show that the addition of volatile acetone effectively reduces the viscosity of PVDF spinning solution,and also increases the curing rate of PVDF membrane,which is beneficial to the formation of fibrous membrane during the direct-writing process.In addition,when the voltage is 3.5 kV,the receiving distance is 10 mm,and the extrusion rate is 0.25 mL/h,the obtained PVDF fiber membrane exhibits regular pore shape and a secondary structure of porous spherulite.When the DMAc/acetone volume ratio is 4∶1,the pore shape of membrane is square.And when the pore size is set to 0.3 mm and the printed layers are 5,the obtained PVDF fiber membrane has a static water contact angle of 117°,and the oil contact angle is nearly 0°.The PVDF fiber membrane has a tensile strength of 399.8 kPa and an elongation at break of 17.37%,showing good mechanical properties.In addition,the kerosene oil fulx reaches 1193.66 L/(m^2·h)under very low operating pressure(-0.01 MPa).It was used in the oil-water separation process almost at self-weight(height of 10 cm),the PVDF membrane has a stable oil flux of 1066.67 L/(m^2·h),with a separation efficiency of 98.27%.After being used for 10 times,the oil-water separation efficiency remains about 98%,showing excellent cycle performance.