Solution blowing (SB) is a promising and scalable approach for the production of nanofibers. Air pressure, solution flowrate, and nozzle-collector distance were determined as effective process parameters, while solution concentration was also reported as a material parameter. Here we performed a parametric study on thermoplastic polyurethane/dimethyl formamide (TPU/DMF) solutions to examine the effect of such parameters on the resultant properties such as fiber diameter, diameter distribution, porosity, and air permeability of the nanofibrous webs. The obtained solution blown thermoplastic polyurethane (TPU) nanofibers had average diameter down to 170 6 112 nm, which is similar to that observed in electrospinning. However, the production rate per nozzle can be 20 times larger, which is primarily dependent on air pressure and solution flow rate (20 mL/h). Moreover, it was even possible to produce nanofibers polymer concentrations of 20%; however, this increased the average nanofiber diameter. The fibers produced from the TPU/DMF solutions at concentrations of 20% and 10% had average diameters of 671 6 136 nm and 170 6 112 nm, respectively. SB can potentially be used for the industrial-scale production of products such as nanofibrous filters, protective textiles, scaffolds, wound dressings, and battery components.

In this paper, the active photovoltaic fibers consisting of nano-layers of polymer-based organic compounds are presented. A flexible solar cell, including a polymer-based anode, two different nano-materials in bulk heterojunction blends as the light absorbing materials, and a semi-transparent cathode to collect the electrons, was formed by coating these materials onto flexible polypropylene (PP) fibers layer by layer, respectively, to produce electricity. Photovoltaic performances of the fibers were analyzed by measuring current versus voltage characteristics under AM1.5 conditions. The maximum value obtained as the short-circuit current density of photovoltaic fibers was 0.27 mA/cm2. The fabrication issues and also possible smart textile applications of these photovoltaic fibers were discussed.

We use polypropylene (PP, an apolar polymer) and cellulose nano whiskers (CNW, a polar material) to produce nano polymer composites with enhanced mechanical and thermal properties. To improve compatibility, maleic anhydride grafted PP has also been used as a coupling agent. To enhance the uniform distribution of CNW in the composite, the matrix polymer is dissolved in toluene, and sonification and magnetic stirring are applied. Good film transparency indicates uniform CNW dispersion, but CNW domains in the composite film observed under an scanning electron microscope may indicate slight agglomeration of CNW in the composite film. The tensile strength of the composite compared with neat PP improves by 70-80% with the addition of CNW. The crystallinity has also been improved by about 50% in the CNW reinforced samples. As the content of CNW increases, the composite exhibits higher thermal degradation temperature, higher hydrophilicity, and higher thermal conductivity.

As one of the nanofiber production processes, the electrospinning process has a conventional configuration consisting of a charged syringe and a grounded collector plate. In this study, the polarities of the electrodes are reversed so that while the collector is charged by power supply, the syringe is grounded. A solution of 7.5 wt % polyvinyl (alcohol)/water is electrospun. The conventional setup and the new inverse setup are compared in terms of production efficiency and the diameter of the nanofibers is produced. Thus, it is aimed to determine which configuration best suits for an extruder-collector system in an industrial context. Results showed that the conventional setup has a noticeably higher nanofiber production efficiency than the new setup due to a lack of Coulombic force acting on the polymer jet in the new setup. Also, nanofiber diameters and web layer pore sizes produced by the conventional setup are much finer and more homogenously distributed than those produced by the new reversed setup.

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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.

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