Polymer fibers electrospun using pulsed voltage

Electrospinning processes are commonly conducted with direct-current voltage (DCV) but the fibers can also be electrospun using a pulsed voltage (PV). Although this method has been used in other electrostatic processes, there is little research on its application in nanofibers production. In this work, the voltage was supplied to the polymer solution in pulses with a given amplitude, frequency, and duration. Experiments were performed with two polymers (polyvinylpyrrolidone and polylactide) using both DCV and PV. The shape of the liquid jet formed at the nozzle tip was observed and linked to the structure of the polymer mats, including the diameters of the electrospun fibers and the sizes and the concentrations of spherical elements. Some differences in products electrospun using DCV and PV were observed both for polyvinylpyrrolidone and polylactide. The parameter that most strongly influenced the examined properties of the polymer mats was the pulse frequency. Moreover, for polylactide the PV method eliminates polymer clogging, providing greater stability of the electrospinning and changes the distribution of fiber diameters into a bimodal one. In general, PV gives better control over fiber diameters and bead sizes because of the possibility of more precise electric charge delivery due to a lower effective voltage. [Display omitted] •Fibrous mats obtained in the electrospinning process with direct-current (DCV) and pulsed (PV) voltages are compared.•The solution shapes at the nozzle tip were observed and linked to the structures of the polymer mats.•The average fiber diameter, the bead size (in the bead-on-string type structure) and their concentration were determined.•Electrospinning with PV is possible and, in some cases, may result in more favorable effects than with DCV.•Preliminary predictions in the structure of electrospun products can be made by observing the meniscus at the nozzle tip.