In this work, the effects of processing parameters on the
morphology of individual electrospun PEO nanofibers and
the properties of electrospun non-woven fiber textiles has
been explored. We have found that the morphology of the
nanofibers produced is influenced strongly by parameters
such as feed rate of the polymer solution, the electrospinning
voltage, and the properties of the solution such as concentration,
viscosity and surface tension. Increasing electrospinning
voltage changed the shape of the surface from which the electrospinning
jet originates. This shape change, which corresponds
to a decrease in the stability of the initiating jet as the
voltage is increased, has been correlated with an increase in the
number of bead defects forming along the electrospun fibers.
In addition, the onset of bead defect formation is shown to
signal a change in the slope electrospinning current as a function
of voltage. The properties of PEO solutionswere found to
define the processing window, and to influence the size and
size distribution of nanofibers significantly.
The properties of solutions from which PEO fibers could
be electrospun ranged from 4 to 10 wt% concentration and
J.M. Deitzel et al. / Polymer 42 (2001) 261–272 271
Fig. 15. Photomicrograph of a PEO webs electrospun from a 2 wt% solution
onto an aluminum grid.
Fig. 16. 3D structure in a non-woven fiber mat electrospun from a 7 wt%
solution of PEO in water electrospun at 11 kV onto a cloth substrate.
hadviscositiesandsurface tensionsin the rangesof1– 20 poise
and 55–35 dynes/cm, respectively. The diameter of the electrospunPEOfiberswas
found to increasewith solutionconcentration
according to a power lawrelationship. Fibers spun from
solutions at concentrations of 8 wt% and higher, exhibited a
bimodal distribution of diameters. Although this behavior has
precedence in that bimodal size distributions have been
observed for droplets formed by the similar process of electrospray,
this is the first time that a bimodal distribution of sizes
hasbeenreportedinapopulationof electrospunpolymerfibers.
General properties of electrospun fiber textiles were also
evaluated. The textiles were found to have specific surface
areas in the rage of 10–20 m2/g. Evaluation of structure by
WAXD and DSC showed poor development of crystalline
order in electrospun fiber mats. Finally, it has been demonstrated
that under appropriate conditions, electrospun fibers
may bemade to organize into heterogeneous or 3Dmacroscale
structures due to electrostatic effects, a property that has implications
for commercial application of the technology