電紡加工條件對紡絲之形貌與直徑之影響

Abstract

傳統紡絲法製造之纖維其直徑多在微米以上，而電紡法是目前製造出微米以下尺度之纖維重要基本方法，其有許多影響成形品的形貌與絲徑的要素，包括操作參數、溶液物性與環境因素，提高高分子溶液濃度可以使得纖維形貌越來越均勻，但是同時纖維絲徑也越來越粗，均勻又細小之產品則為是未來具潛力發展的方向。 本研究以聚乙二醇為溶質，調配純水與乙醇的比例做為溶劑，兩者混和以製成高分子溶液以做為研究，藉以探討是否降低濃度可同時得到均勻又細小之纖維絲。研究中使用黏度計、接觸角儀與電導度計測量溶液物性，高速攝影機觀察電紡成形過程，光學顯微鏡與掃描式電子顯微鏡做為成形品形貌觀察與絲徑計算。 研究結果顯示：溶劑中乙醇占0~50%會使黏度上升，超過50%後黏度反而下降，但因溶劑揮發速率上升所以珠狀物更為減少。濃度越低則乙醇比例需越高才能得到均勻的纖維，但導電度的大幅下降，以高速攝影機的觀察，可知電場拉伸效果下降，在相同操作條件下，濃度與導電度同時下降，纖維絲徑會因導電度大幅下降而先大幅上升，之後才因濃度下降而使纖維絲徑下降。

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.