A Review on the Fabrication of Electrospun Polymer Electrolyte Membrane for Direct Methanol Fuel Cell

Table 4

Electrospinning parameters and their effects on fiber morphology and fiber diameter.

Parameter	Remarks	Reference
Applied voltage	Deposition pattern of fibers changes from random orientation into a straight arrangement.; Fiber bead density increases with increasing instability due to the increase of the applied voltage.; Increasing applied voltage, thinning the fiber, reducing average diameter of the fiber, and causing multiple jets.; Higher applied voltage broadens the distributions of the diameters of fiber.	[85–88]
Distance between tip and the collector	Jet diameter decreases with increasing distance.; At short distance, the fibers are not completely stabilized and eventually the cross-sections of spun fiber become flatter and some fibers stick together becoming bundle fiber.; At long distance, the fibers exhibit a straight; cylindrical morphology indicates the fiber mostly dried when reaching the collector.	[85, 87]
Concentration	Below critical concentration, the fiber jet will break down due to generation of mixture of fibers and droplets jet.; Above the critical concentration, a stable jet is difficult to form.; Bimodal distribution of fiber diameters is possible to form from higher concentration solutions.; Decreasing concentration will reduce the diameter of electrospun fiber; further decrease will form beaded fibers.	[85, 86, 88]
Viscosity	Too diluted solution is difficult to form a stable jet; the jet will break whereas too viscous solution will make it difficult to form fiber due to the solution drying at the tip.; Higher viscosity produces fiber without beads.	[85, 89]
Surface tension of solution	Reduced surface tension will produce fibers without beads.; Reduced surface tension will form a larger diameter of the fibers.; (Depending on polymer and solvent.)	[89]
Net charge density	Adding NaCI or salts will increase the net charge density and reduce diameter of the fiber.	[88, 89]
Feeding rate	At higher feeding rate, this will exceed the delivery rate of solution with applied voltage and eventually result in tiny drops of jet on the collector.; At low feeding rate, the solution is ejected faster and the shift of the mass balance will result in sustained but unstable jet which eventually forms fiber with beads.	[87]
Molecular weight	Molecular weight affects the manipulated concentration in order to electrospin fine fibers.; Low molecular weight can easily form nonuniform fibers with bead.; High molecular weight will be able to produce uniform fibers without bead.	[88]