Water treatment to reduce the porosity of nanowebs: A novel way

One of the main properties of nanofiber webs is their porosity, and any application needs its porosity value. There are many applications which they high or low porosities. Electrospinning is a way to get high porosity, but in some applications, higher or lower porosities than electrospun webs are needed. Up to now, removing one part of the nanofiber web has been used to change the porosity. Here, a new way is introducing for reducing the porosity of the nanowebs, which chose a hydrophilic nanofiber as one part. In the past, only hydrophobic one’s use. We can get the visa versa results. Here a way used to reduce the porosity of the electrospun web which removed PVA nanofibers from PVA/PA6 hybrid nanoweb by water treatment. Measuring the porosity of the electrospun web before and after treatment by the BET method, density method, and image processing proved this. The specific surface area of the web was 70 % reduced after water treatment. After water treatment, the surface roughness and pore volume reduce. Also, the best way introduced for measuring the porosity. Image processing introduces as the best method for measuring the porosity of the nanowebs.

Sound absorption and thermal insulation properties of composite thermoplastic polyurethane/polystyrene (TPU/PS) nanofiber web and TPU nanofiber web and PS-extracted TPU/PS microfiber web

In this study, composite thermoplastic polyurethane (TPU)/polystyrene (PS) nanofiber web and TPU nanofiber web and PS-extracted TPU/PS microfiber web have been experimentally investigated with regard to sound absorption and thermal conductivity coefficients to observe a potential use in sound and thermal insulation areas. Moreover, other properties such as surface area, morphology, tensile strength/elongation, air permeability, and thermal degradation have been analyzed. It has been observed that nanofiber web properties such as fiber diameter, extensibility, pore volume, and porosity have been clearly changed by Soxhlet extraction of PS from the composite TPU/PS nanofibers. PS-extracted TPU/PS fibers can be preferred for the low frequency (600–800 Hz) due to higher SAC (0.7). On the other hand, TPU nanofibers were more effective at medium frequencies (around 3000 Hz, SAC 0.6). Both TPU and PS-extracted TPU/PS composite fibers had similar thermal conductivities, whereas TPU/PS composite nanofibers had lowest thermal conductivity (0.05 W/mK) with moderate maximum SAC value (around 1000 Hz, SAC 0.5–0.6).

Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/nylon 6 nanofiber web treated with repetitive coating cycles and dimethyl sulfoxide multi-step treatment for electronic textiles

Highly conductive nylon 6 nanofiber web was fabricated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and dimethyl sulfoxide (DMSO) for electronic textiles. To improve electrical conductivity, repeated coating with PEDOT:PSS and multi-step treatment of DMSO was performed. The effects of these treatments on electrical conductivity, surface properties, and chemical structures were investigated. For repetitive coating cycles, pristine PEDOT:PSS dispersion was dropped onto a nylon 6 nanofiber web for between one and four times of coating. For DMSO multi-step treatment, in the one-step treatment, the nanofiber web was repeatedly treated using PEDOT:PSS doped with DMSO. In the two-step treatment, the nanofiber web was repeatedly treated with doped PEDOT:PSS at first and, then, it was immersed in a DMSO bath. As a result, the sheet resistance decreased dramatically as the number of coating cycles increased. When the two-step treatment was applied, the sheet resistance was much lower compared to that of the one-step treatment, and thereby sample PD4-D with the lowest resistance showed 6.56 Ω/sq. As a result, the surface of the nanofiber web was covered with more PEDOT:PSS as the coating cycle was repeated. The PEDOT particles became large and long shapes after the two-step treatment of DMSO. This inferred that the contact area among conducting PEDOT particles increased because insulating PSS was removed by DMSO. In addition, the presence of PEDOT:PSS and nylon 6 was confirmed. This study proved that the simultaneous treatments of repeated coating with PEDOT:PSS and multi-step treatment of DMSO can improve electrical conductivity, and it developed the highly conductive PEDOT:PSS/nylon 6 nanofiber web.

Nylon 6 Nanofiber Web-Based Signal Transmission Line Treated with PEDOT:PSS and DMSO Treatment

Highly conductive nylon 6 nanofiber webs, incorporating poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and dimethyl sulfoxide (DMSO), were prepared for textile-based signal transmission lines. To improve the electrical performance of the textiles, they were optimized by the number of coating cycles and the solvent treatment step. The nanofiber web coated four times with PEDOT:PSS showed a six-times reduction in sheet resistance compared to that of once. In addition, the sample treated with both adding and dipping of DMSO showed a significant decrease of 83 times in sheet resistance compared to the sample without treatment of DMSO. Using samples with excellent electrical conductivity, the waveforms of the signal in the time domain were analyzed and shown to have an amplitude and phase almost identical to that of the conventional copper wire. As a result of the S21 characteristic curve, selected textiles were available up to the 15 MHz frequency bandwidth. In the FE-SEM image, it was observed that the surface of the coated sample was generally covered with PEDOT:PSS, which was distinguished from the untreated sample. These results demonstrate that the nanofiber web treated with the optimized conditions of PEDOT:PSS and DMSO can be applied as promising textile-based signal transmission lines for smart clothing.

Fabrication and Electrochemical Characterization of Sulfurized-Polyacrylonitrile Nanofiber Electrodes for Na/S Batteries Using Various Polyacrylonitrile Solutions

A polyacrylonitrile (PAN) nanofiber web was prepared by electrospinning PAN solutions with dimethyl sulfoxide (DMSO) or Dimethylformamide (DMF) as solvent. The PAN web was heated with sulfur to synthesize a sulfurized polyacrylonitrile (SPAN) nanofiber web. The shape of the SPAN web was found to depend on concentration of the PAN solution and properties of the solvent. The SPAN web synthesized using 8 wt% PAN solution in DMSO showed the highest capacity of 1053.3 mAh g−1sulfur under a current density of 526 mA g−1sulfur. Thus, we determined that DMSO could be a potential solvent for preparation of SPAN web electrodes.

Preparation of Poly-1-butene Nanofiber Mat and Its Application as Shutdown Layer of Next Generation Lithium Ion Battery

Nonwoven nanofiber webs from polyolefin show great potential in various fields such as nanofilters, high performance membranes and separators in lithium ion batteries (LiB). Although nonwoven microfiber webs can be obtained by the well-established melt-blown method, it is relatively difficult to produce nonwoven nanofiber web using polyolefin (polyethylene and polypropylene). There have been several reports on the preparation of polyolefin nanofibers by melt-electrospinning, although this approach presents several intrinsic disadvantages, i.e., high processing costs, the requirement of complex equipment, and poor control over pore size or fiber diameter. Solution-based electrospinning has the potential to overcome the drawbacks of melt-electrospinning, but the solubility of most polyolefin is poor. In this study, we found that poly-1-butene, a member of the poly(alpha-olefin) family, can be used in the electrospinning process. We set the concentration of the polymeric solution for electrospinning at 0.65–1.7 g/mL. Here, we report on the fabrication of nonwoven fiber webs composed of poly-1-butene and their copolymers. The diameter of the nonwoven fiber mat was 0.2–0.4 μm, which can be applicable for shutdown layer. As a representative application, we prepared a poly-1-butene nanofiber separator with an appropriate pore size by electrospinning for use as the shut-down layer of a next-generation LiB. The PB-based nanofiber mat provided shutdown ability at around 100 to 120 °C.