Fine fibers spun by electrospinning process from polymer solutions and polymer melts in air and vacuum: Characterization of structure and morphology on electrospun fibers and developing a new process model.

摘要

The electrospinning process is used to make fine fibers with diameters in the range of nanometers to microns. In this process, when the force from an electric field at the surface of polymer solutions or melts is larger than the surface tension force, an electrically charged jet is formed and ejected. The jet dries and solidifies, resulting in fibers, which are collected on a metal screen. The process produces fine fibers with a high surface area to volume ratio. Electrospun fibers can be used to make nonwoven fabrics, reinforcing fibers, supports for enzymes, pesticide carriers for plants, and solar sails.; The objectives of this dissertation were: to produce fine fibers from several different polymer solutions and melts in air and vacuum by the electrospinning process; to characterize the structure and morphology of electrospun fibers using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM); and to describe the electrospinning process using a newly developed process model.; Fibers were electrospun from both conventional and new polymeric materials which are known to have high strength, high modulus, and good thermal stability. Poly(ethylene terephthalate) fibers with diameters of one micron or less were obtained from polymer solutions. Electron diffraction patterns showed d-spacings which agreed with reported values. Poly(amic acid) fibers with diameters ranging from 45 nanometers to a few microns were electrospun from a solution of poly(amic acid) in N-methylpyrrolidnone (NMP).; Poly(ethylene terephthalate) fibers were spun from the melt in air using a combination of electrical force and mechanical force from a take-up spool. A new system for electrospinning in a vacuum was developed from which both poly(ethylene) and poly(ethylene terephthalate) fibers were successfully spun.; A new model was developed to describe the electrospinning process. The model showed the relationships between applied voltage, electrical charge, fiber geometry, fiber velocity, mass flow rate, and electrical current.