Study On Electrospinning Of Fluoro Polymers And Its Application

Electrospinning has been found to be a viable technique to produce nanofibers. Electrospinning origins from that electrically charged fluid is forced jets in the high voltage electrostatic field. The as-prepared fibers with diameter ranging from tens of nanometers to several micrometers deposite randomly to form mats with pore-size of 0.1-10μm. The mats with high surface area and porosity may be applied in areas such as catalysis, filtration, tissue scaffolds, drug delivery systems, protective textiles, separator of cells. In this paper, nanofiber mats of fluoro polymers were prepared by electrospinning and the structures, mechanical properities, water contact angles of the nanofiber mats for potential application on polymer electrolyte barrier of lithium-polymer cells were also investigated.Fluoro polymers were electrospun into nanofiber mats from their solutions in the mixture of N,N-dimethylformamide (DMF) and acetone. Influence factors were analyzed including concentration of solution, ratios of different components of solvent, flow rate and distance between the capillary tip and the collector. The mechanical properities of the electrpspun fluoro polymer membranes were examined. The concentration of solution has a singnficant influence on the morphology of the as-electrospun fibers. The results show that diameter of the fibers increased with the concentration increasing. The fiber mat electrospun from solution with mixture of DMF and acetone with volume ratio of 8:2 has homogeneous morphology than that from solution with DMF used as solvent. The diameter of the fibers increased with the increase of flow ratio. The distance between the capillary tip and the collector has little influence on the morphology and distribution of diameter of fibers. PVDF fiber mats had tensile strength of about 20MPa. PVDF-TFE fiber mat electrospun from solution with concentration of 30% has tensile strength of 13.60MPa but that electrospun from solution with concentration of 20% has tensile strength of 5.15MPa. Almost all the electrospun PVDF-HFP fiber mats have tensile strength more than 22MPa.Nano-porous nanofiber mats of fluoro polymer were prepared by a combination of phase separation and electrospinning. Morphologies of the nano-porous nanofiber mats were observed in detail by field emission scanning electron microscope (FESEM). The mechanical properities of the nano-porous fiber mats were also measured. The FESEM images show the formation of nanopores on the surface of fluoro polymer nanofibers. The molecular weight of PVP of porogen plays an important role on the surface structure of nano-porous fibers. With the molecular weight of PVP increasing, the average diameter of nano-porous fibers increases. Nano-porous fluoro polymer fiber mats with PVP K30 used as porogen has highest tensile strength. The nano-porous fiber mats of PVDF-HFP have similar tensile strength and Young's modulus as the content of PVP of porogen changed.A primary investigation was conducted using electrospun fluoro polymer fiber mats as electrolyte barriers for lithium ion polymer batteries. Electrospun PVDF fiber mats have the porosity of 212.0% and the PVDF electrolyte fiber mat has ionic conductivity of 1.92×10-3S/cm at room temperature. Nano-porous PVDF fiber mats with PVP K30 used as porogen had similar porosity and ionic conductivity to the electrospun PVDF fiber mats. Electrospun PVDF-HFP fiber mat has the porosity of 161.4% and the PVDF-HFP electrolyte fiber mat shows lower ionic...