【作者】 赵治贞；

【导师】 袁晓燕；

【作者基本信息】 天津大学 ， 材料学， 2004， 硕士

【摘要】 本文采用聚偏氟乙烯(PVDF)的 N,N-二甲基甲酰胺和丙酮的混和溶液进行静电纺丝，讨论了混和溶剂的体积配比、溶液浓度、电压、接收距离和溶液流速等系统参数和过程参数对电纺过程和所得 PVDF 超细纤维的形貌及直径分布的影响，表征 PVDF 电纺膜的力学和热性能,以期在锂二次电池电解质隔膜等方面获得应用。 本文对电纺各种影响因素进行研究，用扫描电镜观察电纺所得的PVDF超细纤维的形貌。使用静止的接收屏，分别测定不同浓度和不同混和溶剂配比时溶液的表面张力、电导率和粘度，分析了以上两种因素及其它电纺过程参数的改变对电纺及超细纤维形貌的影响。结果表明，溶液浓度和混和溶剂配比的变化对电纺影响较为明显。当溶液浓度从 10%增大到 17%时，溶液粘度呈增加趋势，所得超细纤维的直径分布范围从 50nm-400 nm变为200 nm-500 nm。浓度为10%时，电纺得到珠丝形貌; 浓度为15%和17%时，所收集到的纤维形貌比较规整; 溶液浓度进一步增加，由于粘度迅速增大，在电纺过程中越来越不容易收集到超细纤维。随着丙酮在混和溶剂中的含量不断增加，溶液的电纺过程中喷射细流在接收屏上成片汇聚的现象明显减少；纤维膜的形貌逐渐变得清晰，纤维膜表面的珠丝逐渐减少，当丙酮在溶剂体系中体积比为 20%时，所得纤维膜中基本不出现珠丝，所得超细纤维的直径分布范围为40 nm-500 nm。电纺溶液的流速从 0.3 mL/h 增大到 0.5 mL/h 时，所得纤维的形貌变化不明显，所得超细纤维的直径分布范围均集中在100 nm-400 nm 之间。电压从5 kV 增大到10 kV时，静电纺丝过程和纤维形貌变化不明显，所得超细纤维的直径分布范围均集中在 200 nm-400 nm之间。接收距离从 10 cm 增大到 20 cm 时，收集到纤维的形貌变化不大，所得超细纤维的直径分布范围均集中在 100 nm-300 nm 之间。本文中对 PVDF/DMF/丙酮体系进行电纺的最佳条件是溶液浓度为 15%、DMF/丙酮为 8:2、电压为 5 kV、流速为 0.3 mL/h和接收距离为15 cm。 用金属转筒包裹铝箔作为转动接收装置进行电纺，经8-10小时后可收集到具有膜厚度为20 μm -50 μm 之间的PVDF超细纤维膜。将所得纤维膜烘干，测得PVDF超细纤维膜中的溶剂残留量为0.38%-0.66%。将所得纤维膜制成70 mm×10 mm 的样条进行拉伸试验，结果表明，所得PVDF电纺超细纤维膜的力学性能各向异性不明显，这表明纤维膜中的纤维没有发生明显的取向，而是呈无规的杂乱排布。溶液浓度从 10%增大到17%，所得 PVDF 超细纤维膜的拉伸强度和拉伸模量呈下降趋势，分别由 126.3 MPa 和113.0 MPa 降至 21.59 MPa 和 24.97 MPa。通过差示量热扫描和广角 X 光衍射方法，分析了电纺所得 PVDF 超细纤维膜和原料的结晶行为差异，结果表明，随着 PVDF 溶液浓度的增加，所得电纺纤维膜与原料相比，结晶度有少许增大，结晶形态基本相同。更多还原

【Abstract】 Polyvinylidene fluoride (PVDF) were processed into fibrous membranes byelectrospinning from its solutions in the mixture of N,N-dimethylformamide (DMF)and acetone in this paper. Influencing factors were mainly discussed, includingapplied voltage, concentration of solution, flow rate, collecting distance and ratios ofdifferent components in solvents. The thermal and mechanical properties of theelectrospun PVDF membranes were examined. These electrospun PVDF fibrousmembranes would be potentially applied in electrolyte separators in Lithiumsecondary batteries. The morphology of the electrospun PVDF fibrous membranes was investigatedby scanning electron microscopy. Surface tension, viscosity and conductivity of thePVDF solutions were measured at different concentrations and different ratios ofcomponents. Their changes also had influence on the morphology of the electrospunfibers. Results showed that polymer concentration and ratios of different componentsin solvents had evident influence on the electrospinning process. With theconcentration changing from 10%-17%, the process of electrospinning became moreand more difficult because of increase of viscosity and the distribution of fibersdiameter changed from 50 nm -400 nm to 200 nm -500 nm. It is suggested thatuniform ultrafine fibrous membranes could be obtained when the concentration was15%. With the concentration increasing, the density of beads and beaded fibersdecreased and the morphology became much more orderly. The diameter showed adecrease tendency with increase of the acetone amount in the solvent mixture and thedistribution of fiber was in 40 nm -500 nm when the amount of acetone was 20% inthe solvents. There was no clear difference in morphology when the flow rate increasedfrom 0.3 mL/h to 0.5 mL/h, and the distributions of the fibers diameters both focused on the rangeof 100 nm -400 nm. When the voltage increased from 5 kV to 10 kV, there was littledifference in the morphology and the distribution of fibers diameter both focused on200 nm-400 nm. The deposition distance had little influence on the morphology offibers and the distribution of fibers diameter focused on 100 nm -300 nm. In thisexperiment, the best condition for PVDF electrospinning was that the acetone amountin the solvents was 20%, the concentration was 15%, the voltage was 5 kV, the flowrate was 0.3 mL/h and the deposition distance was 15 cm. A revolving canister connected with ground was selected as a collector, whichwas covered with aluminium foil. And the obtained membrane was about 20 μm-50μm in thickness electrospinning for 8-10 hours. A series of typical stress-strain curves ii<WP=5>were obtained via a group of samples which shape was made to 70 mm×10 mm inpulling experiments. The tropism of fibers was not clear and the distributing of fiberswas disordered. With the increase of concentration, the performance of membranedecreased from 126.3 MPa and 113.0 MPa to 21.59 MPa and 24.97 MPa. The fibrousmembranes were made dry in vacuum oven and the remains in the solvents wereaccounted about 0.38%-0.66%. The crystallization was analyzed via differentialscanning calorimetric and wide angle X-ray diffraction to find their difference. Andthe crystallization of PVDF membrane enhances a little with the increase of solutionconcentration.更多还原