Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-0613103-130015


Document Typethesis
Author NameTao, Jing
URNetd-0613103-130015
TitleEffects of Molecular Weight and Solution Concentration on Electrospinning of PVA
DegreeMS
DepartmentMaterials Science & Engineering
Advisors
  • Satya Y. Shivkumar, Advisor
  • Chrysanthe Demetry, Committee Member
  • Richard Sisson, Department Head
  • Keywords
  • concentration
  • molecular weight
  • PVA
  • electrospinning
  • structure
  • Date of Presentation/Defense2003-06-12
    Availability unrestricted

    Abstract

    The effects of molecular weight (Mw) and concentration (c) on the structure of electrospun PVA have been studied. Experiments have been conducted for Mw values ranging from 9000 g/mol to 124,000 g/mol. The concentration was varied from 5 to 35 wt %. Data were acquired for several solvents including water, Dimethyl Sulfoxide, Ethylene Glycol and N-Methyl Pyrrolidone. The transient phenomena occurring during jet breakdown were examined by high speed digital photography. The structure in the electrospun polymer was analyzed by scanning electron microscopy. The fiber diameter distribution for various conditions was characterized by optical image analysis. The effects of additives such as NaCl and Poly Ethylene Glycol on the structure have been studied. The results indicate that a minimum Mw and c corresponding to [h]c ~ 5 or Capillary number, Ca ~ 0.5 is necessary for forming a fibrous structure. As Mw or c increase, the fiber diameter becomes larger and a broader distribution of fibers may be obtained. The average diameter of the fiber, D, follows a Power law relationship: D (nm) = 18.6([h]c)1.11. Round fibers may be obtained at low Mw and c, while flat fibers are observed at high Mw and c. The transition from round to flat fibers appears to begin at [h]c ~ 12. At any [h]c, there is a minimum Capillary and Ohnesorge numbers at which fibers are stabilized and a maximum at which viscous effects become dominant. The addition of NaCl lowers the average fiber diameter in PVA samples with a high molecular weight. Electrospinning can be used to produce nanofibers of PVA with various architectures.

    Files
  • jtao.pdf

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