| Electrospinning is a superior process compared to other conventional spinning methods for the production of fibers in sub-micron to nanometer diameters. Such fiber membranes have exceptionally large surface areas and small pore sizes. The process requires an electrostatic force at the surface of a polymer solution or melt, which overcomes the surface tension and viscoelastic forces to create an electrically charged jet. When the jet stream dries or solidifies, an electrically charged fiber remains, which can be directed or accelerated by the electrical forces and then collected in non-woven fiber membrane or other useful shapes. The current work demonstrates the electrospinning of polycarbonate dissolved in solvent mixtures of tetrahydrofuran and dimethylformamide to obtain fibers on the nanoscale. The solvent mixtures played a significant role on the morphology of the fibers. The spun fibers showed the characteristics of strong networking to each other as the THF ratio was raised in the solvent mixtures (such as 60:40, 70:30 of THF: DMF). The electrostatic voltage, viscosity and surface tension also had major effects on the fiber morphology and formation of beads. At lower THF and DMF ratios and lower spinning voltages, the bead revealed a globular mushroom shape, while at higher ratios and higher voltages, the beads formed the shape of a spindle. The microstructures of the electrospun polycarbonate fibers were quantitively investigated by Scanning Electron Microscope (SEM) and Transmission Electron Microscope as a function of processing variables. |
