Generation of PVP fibers by electrospinning in one-step process under high-pressure CO2

Background: Electrospinning is a process of electrostatic fiber formation using electrical forces to produce polymer fibers from polymer solution in nano/micrometer scale diameters. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years, mostly in solvent solution and some in melt form. In this work, electrospinning was conducted under high-pressure carbon dioxide (CO2) to reduce the viscosity of polymer solution. The experiments were conducted at 313 K and approximately 8.0 MPa. Polyvinylpyrrolidone in dichloromethane was used as a polymer solution with 4 wt.% of concentration. The applied voltage was 17 kV, and the distance of nozzle and collector was 8 cm. The morphology and structure of the fibers produced were observed by scanning electron microscopy. Results: When the CO2 pressure was 5 MPa, the resultant fibers had an average diameter of 2.28 +/- 0.38 to 4.93 +/- 1.02 mu m. The ribbon-like morphology was formed with increasing pressure of CO2 at 8 MPa with a tip 0.75-mm inside diameter. Conclusions: The results show that the depressurization of CO2 at the end of experiment assists the removal process of the polymer solvent and produces the porous nature of fibers without collapsing or foaming. These behaviors hold the potential to considerably improve devolatilization electrospinning processes.