| Summary: | 碩士 === 國立交通大學 === 機械工程學系 === 98 === Traditional fiber spinning always produces fibers with a greater than micro-scale diameter. Electrospinning has been recognized as an efficient technique for the fabrication of polymer nanofibers. The fiber diameter and morphology of fibers produced in this manner are affected by a number of factors, such as processing parameters, ambient parameters, and the properties of constituent solutions. Uniform electrospun fibers can be obtained by increasing the concentration of the polymer solution, but this leads to an increase in the thickness of the electrospun fibers. The ability to produce uniform but thin electrospun fibers is the key to future development in the field.
In the study, we prepared a polymer solution using polyethylene oxide as the solute and a mixture of water and ethanol as the solvent. To investigate whether uniform but thin electrospun fibers could be obtained with a lower polymer concentation, we measured the viscosity, surface tension, and conductivity of the polymer solution, with a viscometer, contact angle meter, and conductivity meter, respectively. We observed the electrospinning process by high-speed camera; used optical microscopy to observe the electrospun fibers; and scanning electron-microscope to measure their diameter.
The results of the experimental showed that solution viscosity increase with a 0~50%wt. of ethanol added to the solvent and decreased above 50%. Due to an increase in the evaporation rate of the solvent, we observed a reduction in the number of beads . If the concentration of PEO dropped, the content of ethanol in the solvent would have to be increased, to improve the uniformity of the electrospun fibers. This, however, would lead to a substantial decrease in conductivity. Through observation of the jets with high speed cameras, we determined that the electrical force applied to the jets had dropped. Under identical electrospinning conditions, a decrease in conductivity in the PEO lead to an increase in the fiber diameter; and a decrease in concentration of the PEO led to a decrease in the fiber diameter.
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