Fractionation of Regenerated Silk Fibroin and Characterization of the Fractions

The molecular weight (MW) of regenerated silk fibroin (RSF) decreases during degumming and dissolving processes. Although MW and the MW distribution generally affect polymer material processability and properties, few reports have described studies examining the influences of MW and the distribution on silk fibroin (SF) material. To prepare different MW SF fractions, the appropriate conditions for fractionation of RSF by ammonium sulfate (AS) precipitation process were investigated. The MW and the distribution of each fraction were found using gel permeation chromatography (GPC) and SDS-polyacrylamide electrophoresis (SDS-PAGE). After films of the fractionated SFs formed, the secondary structure, surface properties, and cell proliferation of films were evaluated. Nanofiber nonwoven mats and 3D porous sponges were fabricated using the fractionated SF aqueous solution. Then, their structures and mechanical properties were analyzed. The results showed AS precipitation using a dialysis membrane at low temperature to be a suitable fractionation method for RSF. Moreover, MW affects the nanofiber and sponge morphology and mechanical properties, although no influence of MW was observed on the secondary structure or crystallinity of the fabricated materials.

Production of Styrene-[Ethylene-(Ethylene-Propylene)]-Styrene Block Copolymer (SEEPS) Microfibers by Electrospinning

Thermoplastic elastomer-based fibers have many advantages including lightness, flexibility, resilience. Styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS) is a styrenic block copolymer based thermoplastic elastomer and it can be used for many applications with many functions as a matrix, compatibilizer, modifier or adhesive. It has good resistance to oxidizing agents, weathering, aging, and it can be used under various conditions. In this study, SEEPS block copolymer fibers were electrospun. This study is the first study about the electrospinning of SEEPS block copolymer in the literature. Various spinning solutions were used, and process was optimized by changing the electrospinning conditions. Fiber morphology was analyzed by an optical microscope and fiber diameter distribution histograms were drawn. In order to understand the effects of polymer concentration on electrospinning, viscosity of the spinning solutions was measured. Although electrospinning conditions were found to be critical in terms of spinnability, solution concentration and viscosity were the most significant factors for obtaining flexible SEEPS based fibrous nonwoven mats.

Evaluation of Polyacrylonitrile Nonwoven Mats and Silver–Gold Bimetallic Nanoparticle-Decorated Nonwoven Mats for Potential Promotion of Wound Healing In Vitro and In Vivo and Bone Growth In Vitro

We prepared polyacrylonitrile (PAN) and urchin-like Ag–Au bimetallic or Ag nanoparticle-decorated PAN nonwoven mats using electrospinning and evaluated them in vitro and in vivo for wound healing, antibacterial effects on skin tissue, and promotion of bone ingrowth in vitro. A facile, green, low-temperature protocol was developed to obtain these nonwoven mats. The sterilization rate of urchin-like Ag–Au bimetallic and Ag nanoparticle-decorated PAN nonwoven mats against Staphylococcus aureus was 96.81 ± 2.81% and 51.90 ± 9.07%, respectively, after 5 h treatment. In an in vitro cell model, these two mats did not show significant toxicity; cell viability of >80% was obtained within 5 h of treatment. In vivo animal model preclinical assessment showed that the urchin-like Ag–Au bimetallic nonwoven mat group showed significant wound recovery because of sebaceous gland, hair follicle, and fat formation during skin tissue regeneration; increased neovascularization and compact collagen fibers were observed in the dermal layer, comparable to the findings for the control group. The mother substrate of the urchin-like Ag–Au bimetallic nanoparticle-decorated PAN nonwoven mats, that is, pure PAN nonwoven mats, was found to be a potential scaffold for bone tissue engineering as osteoblast ingrowth from the top to the bottom of the membrane and proliferation inside the membrane were observed. The key genetic factor Cbfa1 was identified as a key osteoblast differentiation regulator in vitro. Thus, electrospun membrane materials show potential for use as dual-functional biomaterials for bone regeneration and infection control and composite grafts for infectious bone and soft tissue defects.

Recrystallization of CsPbBr3 Nanoparticles in Fluoropolymer Nonwoven Mats for Down- and Up-Conversion of Light

Inorganic halides perovskite CsPbX3 (X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) nanoparticles are efficient light-conversion objects that have attracted significant attention due to their broadband tunability over the entire visible spectral range of 410–700 nm and high quantum yield of up to 95%. Here, we demonstrate a new method of recrystallization of CsPbBr3 nanoparticles inside the electrospun fluoropolymer fibers. We have synthesized nonwoven tetrafluoroethylene mats embedding CsPbBr3 nanoparticles using inexpensive commercial precursors and syringe electrospinning equipment. The fabricated nonwoven mat samples demonstrated both down-conversion of UV light to 506 nm and up-conversion of IR femtosecond laser radiation to 513 nm green photoluminescence characterized by narrow emission line-widths of 35 nm. Nanoparticle formation inside nonwoven fibers was confirmed by TEM imaging and water stability tests controlled by fluorimetry measurements. The combination of enhanced optical properties of CsPbBr3 nanoparticles and mechanical stability and environmental robustness of highly deformable nonwoven fluoropolymer mats is appealing for flexible optoelectronic applications, while the industry-friendly fabrication method is attractive for commercial implementations.

The Development of High-Power LIBs Separators

Separators present the crucial functions of separating the positive and negative electrodes due to the free flow of lithium ions through the liquid electrolyte that fills in their open pore. Separators for liquid electrolyte Lithium-ion batteries can be classified into porous polymeric membranes, nonwoven mats, and cellulose separators. When a lithium-ion battery is being overcharged, it releases the heat and results in the inner-short. The polyethylene (PE) separators used here had shut down at around 135°C to cool the exothermal batteries. To enhance the meltdown temperature of the separator, a PE separator was coated with polymers synthesized from various ethylene glycol dimethacrylate monomers. At the same time, nonwoven mats have the potential to be low cost and thermally stable separators. Furthermore, the lithium-ion phosphate/lithium half cell using cellulose separator exhibited stable charge-discharge capability even at 120 °C. This paper presents an overview of the PE and PP membranes of lithium-ion battery separators, discusses how to solve their disadvantages, and reviews the cellulose-based materials developed for potential application in the lithium-ion battery.

Garment Waste Recycled Cotton/Polyester Thermal and Acoustic Properties of Air-Laid Nonwovens

This research paper reports a study on thermal and sound insulation samples developed from garment waste recycled cotton/polyester fiber (recycled cotton/PET) for construction industry applications. In this research work, the piece of clothing waste recycled cotton and polyester fiber is a potential source of raw material for thermal and sound insulation applications, but its quantities are limited. To overcome the above problems, apparel waste recycled cotton fiber was mixed with recycled/PET fiber in 50/50 proportions in the form of two-layer nonwoven mats with chemical bonding methods. The samples such as cotton (color and white), polyester (color and white), and cotton–polyester blend (color and white) were prepared. All the samples were tested for thermal insulation, acoustic, moisture absorption, and fiber properties as per the ASTM Standard. Also, the behavior of the six recycled cotton/polyester nonwoven samples under high humidity conditions was evaluated. The sound absorption coefficients were measured according to ASTM E 1050 by an impedance tube method; the acoustics absorption coefficients over six frequencies of 125, 250, 500, 1000, 2000, and 4000 Hz were calculated. The result revealed that recycled/PET/cotton garment waste nonwoven mats were absorbing the sound resistance of more than 70% and the recycled nonwoven mats provided the best insulation, acoustic, moisture absorption, and fiber properties. The recycled pieces of clothing waste cotton/polyester nonwoven mats have adequate moisture resistance at high humidity conditions without affecting the insulation and acoustic properties.