The Effects Of Processing Parameter And Whipping On Fiber Morphology In Electrospinning

Electrospinning is a popular technique to produce nanofibers.It is applicable to both natural and synthesis polymers.Because nanofibers have several special properties like small diameter,high surface area to the volume ratio and high porosity,they can be used such as filter membrane,wound dressings,tissue engineering and biomedical engineering extensively.In the electrospinning process,when subjected to strong electric field,the pendant polymeric droplet will deform into a Taylor cone and form a liquid jet.The jet undergoes an electrically-induced bending and whipping instability which results in looping and the stretching of the jet.After quick evaporation of the solvent,ultra-fine fibers will deposit on the grounded collector.In this paper,we use the methods of experimental and simulation to study the whipping process of the electrospinning and its influence on the fiber morphology.In the second and third chapter,we use polyethylene oxide (PEO)/water solution as material to study the effects of parameters include the mass percent concentration of the polymer,applied voltage, flow rate of the solution,the distance between the spinneret and the receiver,the inner diameter of the needle,the content of ethanol,on the electrospun fiber morphology.By measuring of the area of the fiber mat, and employing SEM to investigate the morphology and diameter of the fibers to analyze the influence on the morphology of the fibers.We find that the viscosity and the distance from the spinneret to the collector have greater effects on the fiber diameter,which ranges form 47nm to 378nm. The whipping degree can be derived from the area of the fiber mat.We use X-ray diffraction to analyze the crystallinity of the fibers under different processing parameters and find that electrospinning process can help increasing the crystallinity of the fibers.In the fourth and fifth chapter,simulation and experimental methods are employed to study the influence of whipping in the electrospinning process on the fineness and morphology of the fibers.In the experiments, we employ PEO/water solution and PVA/water solution to study the perturbation in the electrospinning process,and we find that air perturbation plays a certain role in the whipping instability.