Formation of PVP hollow fibers by electrospinning in one-step process at sub and supercritical CO2

• PVP nano-micofibers has been produced via electrospinning under high pressure CO2.
• Hollow fibers with walls made of organic polymer have been successfully formed.
• CO2 improved the solvent devolatilization during electrospinning processes.
• CO2 is shown to be an effective medium for PVP hollow fibers.

It was well known that electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. 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, hollow fibers with walls made of organic polymer composites have been formed by electrospinning in a single processing step under pressurized carbon dioxide (CO2). The experiments were conducted at 313 K and ∼8 MPa. The capability and feasibility of this technique was demonstrated by the production of polyvinylpyrrolidone (PVP) fibers whose size and wall thickness could be independently varied by controlling a set of experimental parameters. The PVP fibers had an average pore diameter 2–4 μm. At low pressures (<5 MPa; subcritical conditions), the solid fibers were formed, the baloon-like structures of PVP was formed with increasing pressure of CO2 at 8 MPa (supercritical condition)