Electrospinning of thermoplastic polyurethane microfibers and nanofibers from polymer solution and melt

Abstract

Electrospinning technique was used to produce ultrafine fibers from thermoplastic polyurethane (TPU). A direct comparison between melt and solution electrospinning of TPU was provided for the evaluation of process-structure relationship. It was found that the deposition rate of melt electrospinning (0.6 g h À1 ) is four times higher than that of solution electrospinning (0.125 g h À1 ) for TPU under the same processing condition. However, the average fiber diameters of solution electrospun TPUs (220-280 nm) were much lower than those of melt electrospun TPUs (4-8 lm). The effect of processing variables including collection distance and electric field strength on the electrospun fiber diameter and morphology was also studied. The findings indicate that increasing the electric field strength yielded more electrical forces acting on polymer jet and resulted in a decrease in fiber diameter as a result of more fiber drawing in both solution and melt electrospun fibers. It was also demonstrated that increasing the collection distance led to an improvement in the solidification of melt electrospun fibers and thus less fused fibers were obtained. Finally, a close investigation of fiber structures revealed that melt electrospun TPU fibers had smooth surface, whereas solution electrospun TPU fibers showed high intensity of cracks on the fiber surface.

Electrospinning of highly aligned and covalently cross‐linked hydrogel microfibers

“…A wider range of diameters can be obtained when using higher molecular weight thickeners. This result is similar to other results found in literature on polymer solution and melts . For a given precursor, thinner fibers are generated at lower thickener concentration as well at lower flow rate and higher voltage.…”

Melt Electrospinning and Its Technologization in Tissue Engineering

“…If the collection distance is increased there is another effect; the fiber has more time to cool down, which increases the viscosity and therefore resistance of the jet to being stretched. As a result the diameter of the fiber arriving to the collector is larger in these cases 40,41,43,57 although this outcome is not always observed. 33,35,44 Larger collection distances also result in a loss of focus of the melt electrospinning jet as it deposits, which is not favorable for direct writing approaches (described later).…”

“…In this case the electrical charge density the jet is subject to is increased and the electrostatic drawing effect is increased. 25,35,38,40,41,45,48,57 However, this phenomenon has not always been clearly observed to have a significant influence on the diameter of the jet. For example, when PCL was melt electrospun using a laser as the heating system, changes in voltage did not significantly change the fiber diameter when using 5-25 kV.…”

Electrospun Polyurethane Nanofibers

“…Several authors investigated the effects of solution and process parameters such as material composition, concentration, rheological properties, applied voltage, tip-to collector distance, collector types on the resultant PU nanofibers [26,27,[47][48][49]. Among these parameters, polymer solution properties have the most significant influences on the process and the resultant fiber morphology [9], since viscoelastic and gravitational forces play a major role.…”