Preparation of polybenzoxazole fibers via electrospinning

• Main Authors: Kuen-Shian Lin, 林坤賢
• Other Authors: Chi Wang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/04521050695826684680

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 93 === 　Polybenzoxazole(PBO) fibers with submicron-scale diameter have been fabricated from the PBO precursor polyhydroxyamide(PHA) by using electrospinning and thermal cyclization processes. The resulting fibers have exceptional mechanical properties and birefringent. In systems a common solvent we used tetrahydrofuran(THF), which evaporates rapidly at room temperature, the solution droplet at the tip dries out very quickly during the formation of the Taylor cone, thereby blocking the tip and making the collection process discontinuous. Several alternatives have been proposed to overcome this problem, we used nitrogen gas to carry saturated gas surrounding the Taylor cone against volatile solvent evaporates immediately. This method can stabilize the system and make process continuous. 　In this study, PHA was dissolved in the mixture of dimethylacetamide (DMAc) and THF. The results indicate that the morphology of the fibers are dependent on the ratio of DMAc and THF mixture. Besides the solution concentration, solvent properties, and nitrogen gas flow rate, and even the condition of thermal cyclization also can affect the formation and morphology of the fibers. 　Using high speed videography , we can observe the rapid motion of cone and jet splaying. In low solution concentration, the cone vibrated up and down very quickly, and produced spheres. In high solution concentration, the liquid jet followed a bending, winding, spiraling and looping path，and the loops formed immediately on the jet. 　The average diameter of electrospun fibers was 719 209nm from a 20wt% solution of PHA in THF/DMAc=9/1. After thermal cyclization processes, PBO fibers can be fabricated and the fiber diameter is 643 212nm. 　In multi-jet electrospinning, the experiment results were dependent on the distance between needles, the distance between needle and collector and the applied voltage. Due to the electric field effect, it can be observed that the deflection of jet increases with decreasing the distance between needles.