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Gas jet process for production of sub-micron fibers.

机译：气体喷射工艺用于生产亚微米纤维。

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摘要

A new, simple, and effective method was developed for production of fibers from polymer solutions with diameters ranging from a few tens of nanometers to a few micrometers. The process, termed gas jet nanofibers (GJF), bears several similarities and contrasts with electrospinning and melt-blowing processes. The method capitalizes on a high velocity expanding gas jet to turn polymer solutions streaming from nozzles into fibers with smooth or wrinkled fiber surface morphology and with core-shell and side-by-side arrangements. The polymer solution is brought in contact with the gas jet on a flat surface, at the tip of a circular needle, and on the surface a pendant drop. The fiber diameter bears relationship with capillary number of the liquid jet and polymer concentration in the solution. Several levels of fiber conglutination are observed as function of the collection distance from the nozzle.;The dynamics of the formation of the fiber in the GJF process was inferred from the high speed video images of the liquid jet emanating from the nozzles. The fiber diameter attenuation was found to originate from flapping and bending instabilities and concurrent solvent evaporation. The fiber is initiated by a single liquid jet formed as the liquid emerges from each nozzle configuration. The liquid jets of diameters from around 40 mum to 600 mum are attenuated to the sub-micrometer level within a small distance from the point of liquid-gas contact.;The process adaptability was demonstrated with several case studies. First, the production of compound fibers with core-shell and side-by-side configurations was studied for pair of immiscible polymers. Polyvinyl acetate (PVAc), polyethylene oxide (PEO), and polyvinyl pyrrolidone (PVP) were used to create compound fibers with different sizes and configurations. Second, the production of bi-component nanofibers with controlled morphology produced from homogeneous solutions of an immiscible pair of polymers in a miscible pair of solvents was developed. The approach is based on evaporation rates of selected solvents and solvent-evaporation-induced phase separation of the polymers during stretching of the liquid jets by the gas flow. The approach yielded nanofibers from blends of polyvinylacetate and polyvinylpyrrolidone with diameters below 500 nm exhibiting several morphological forms after phase separation of the polymers including interpenetrating, bi-lobal, and core-shell.;The gas jet method was also used to produce carbon fibers with diameters ranging from 100 nm to several micrometers from mesophase pitch by using a patented nozzle system. The process is based on force exerted by coaxial hot jets of air on the molten mesophase pitch in the nozzle. The dynamics of the gas jet and the formation of the fibers were studied by using computational fluid dynamics (CFD) models. It was learned that fibers are formed from a combination of ripples and growth of wave perturbations in the interphase between the fiber precursor and air due to the competition between the forces originated from aerodynamics, surface tension, and inertia.
机译：开发了一种新的，简单而有效的方法，用于从直径在几十纳米到几微米的聚合物溶液中生产纤维。该过程被称为气体喷射纳米纤维（GJF），与静电纺丝和熔喷工艺具有几处相似之处并形成对比。该方法利用高速膨胀的气体喷射流，将从喷嘴流出的聚合物溶液转变为具有光滑或起皱的纤维表面形态，并具有核-壳和并排布置的纤维。使聚合物溶液在平面上，圆形针头的尖端和悬垂液滴的表面上与气体喷嘴接触。纤维直径与液体射流的毛细管数和溶液中的聚合物浓度有关。观察到几个水平的纤维粘连，这是从喷嘴收集距离的函数。GJF过程中纤维形成的动力学是从喷嘴喷出的高速视频图像推断出来的。发现纤维直径衰减源自拍打和弯曲不稳定性以及同时发生的溶剂蒸发。纤维由液体喷出时形成的单个液体射流引发。直径约40微米至600微米的液体射流在与液-气接触点的一小段距离内衰减到亚微米水平。该过程的适应性已通过多个案例研究得到证明。首先，研究了成对的不互溶聚合物的核壳结构和并排结构的复合纤维的生产。聚醋酸乙烯酯（PVAc），聚环氧乙烷（PEO）和聚乙烯吡咯烷酮（PVP）用于制造具有不同尺寸和结构的复合纤维。其次，开发了由可互溶的聚合物对在可互溶的溶剂对中的均匀溶液制得的，具有受控形态的双组分纳米纤维的生产。该方法基于所选择的溶剂的蒸发速率以及在由气流拉伸液体射流期间溶剂蒸发引起的聚合物的相分离。该方法由聚乙烯乙酸酯和聚乙烯吡咯烷酮的共混物制得的纳米纤维，其直径低于500 nm，在聚合物相分离后表现出几种形态形式，包括互穿，双叶和核-壳型。通过使用获得专利的喷嘴系统，直径从中间相间距到100 nm到几微米不等。该过程基于同轴热空气射流对喷嘴中熔融中间相沥青施加的力。使用计算流体动力学（CFD）模型研究了气体射流的动力学和纤维的形成。据了解，由于由空气动力，表面张力和惯性产生的力之间的竞争，纤维是由波纹和在纤维前体和空气之间的相间的波动扰动的增长共同形成的。

著录项

  • 作者

    Benavides, Rafael E.;

  • 作者单位

    The University of Akron.;

  • 授予单位 The University of Akron.;
  • 学科 Chemical engineering.;Polymer chemistry.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 198 p.
  • 总页数 198
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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