Ultrafine Fibrous Membranes Research Articles

Electrospun poly (arylene ether nitrile) fibers for interlaminar toughening of carbon fiber epoxy composites

The limited shear strength and interlaminar toughness of carbon fiber epoxy composite laminates restrict their further promotion. Traditionally, interlaminar toughening has been achieved using polymers such as polyamide 66, polyamide 69, and poly (ε-caprolactone), but they are limited by physical or chemical performance. As a potential option, poly (arylene ether nitrile) (PEN) could be considered for interlaminar toughening due to its epoxy compatibility, thermal resistance, and excellent mechanical properties. In this work, we prepared PEN ultra-fine fibrous membranes with different areal densities by electrospinning. The best overall performance was obtained by adding 8 g/m2 of PEN fibrous membranes between the layers. The results indicate that PEN fibrous membranes increased interlayer shear performance by 12%, mode I fracture toughness by 69%, and pendulum impact performance by 6%. This work highlights the potential of electrospun thermoplastic PEN fibers for improving the interlaminar toughening of composite laminates.

Preparation of ultrafine fibrous membrane with TiO2/Bi2SiO5 photocatalyst on eggshell and its degradation of organic dye under visible light

Preparation of ultrafine fibrous membrane with TiO2/Bi2SiO5 photocatalyst on eggshell and its degradation of organic dye under visible light

Molecular Design, Preparation, and Characterization of Fluoro-Containing Polyimide Ultrafine Fibrous Membranes with High Whiteness, High Thermal Stability, and Good Hydrophobicity.

Polymeric ultrafine fibrous membranes (UFMs) with high thermal stability and high whiteness are highly desired in modern optoelectronic applications. A series of fluoro-containing polyimide (FPI) UFMs with high whiteness, good thermal stability, and good hydrophobicity were prepared via a one-step electrospinning procedure from the organo-soluble FPI resins derived from a fluoro-containing dianhydride, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and various diamines containing either pendant trifluoromethyl (–CF3) groups or alicyclic units in the side chains. The obtained FPI UFMs, including FPI-1 from 6FDA and 3,5-diaminobenzotrifluoride (TFMDA), FPI-2 from 6FDA and 2′-trifluoromethyl-3,4′-oxydianiline (3FODA), FPI-3 from 6FDA and 1,4-bis[(4-amino-2-trifluoromethyl)phenoxy]benzene (6FAPB), FPI-4 from 4,4′-bis[(4-amino-2-trifluoromethyl)phenoxy]biphenyl (6FBAB), and FPI-5 from 6FDA and 4′-tert-butyl-cyclohexyl-3,5-diaminobenzoate (DABC) showed whiteness indices (WI) higher than 87.00 and optical reflectance values higher than 80% at the wavelength of 457 nm (R457), respectively. The FPI-5 UFM, especially, showed the highest WI of 92.88. Meanwhile, the prepared PI UFMs exhibited good hydrophobic features with water contact angles (WCA) higher than 105°. At last, the PI UFMs exhibited good thermal stability with glass transition temperatures (Tg) higher than 255 °C, and the 5% weight-loss temperatures (T5%) higher than 510 °C in nitrogen.

Preparation of ultrafine fibrous membranes containing graphitic carbon nitride composited photocatalyst and their degradation of methylene blue under visible light

Preparation of ultrafine fibrous membranes containing graphitic carbon nitride composited photocatalyst and their degradation of methylene blue under visible light

Photo-Patternable, High-Speed Electrospun Ultrafine Fibers Fabricated by Intrinsically Negative Photosensitive Polyimide.

This work describes polyimide (PI) ultrafine fibrous membranes (UFMs) with aligned fibrous structures, fabricated via the high-speed electrospinning procedure. Organo-soluble intrinsically photosensitive PI is utilized as the fiber-forming agent. The effects of different rotating speeds on the fiber morphology and properties are studied. The aligned UFMs possess hydrophobicity, favorable optical properties, and improved deformation durability. The extension strength of the UFMs reinforces obviously with the increased rotating speed and reaches the maximum of 9.18 MPa at 2500 rpm. In addition, due to the photo-cross-link nature of the PI resin, the UFMs present lithography capability, which can obtain micro-sized patterns on aluminum substrates, and even part of the fibrous structure was retained after development. This work shows promise in manufacturing fiber-based photolithographic hierarchical structures on flexible substrates, which exhibit potential in achieving multiple functions on fiber-based electronic devices.

Centrifugally spun starch/polyvinyl alcohol ultrafine fibrous membrane as environmentally‐friendly disposable nonwoven

AbstractWe developed a new environmentally‐friendly disposable nonwoven based on centrifugally spun ST/PVA ultrafine fibrous membrane in this research. The effects of ST/PVA ratio as well as formic acid post‐treatment on thermal properties, tensile strength, and disposability of fibrous membranes were studied. To observe the morphology and chemical structures changing of fibers during fabrication and post‐treatment, the obtained fibers were characterized by scanning electron microscopy, x‐ray diffraction, and Fourier transform infrared spectroscopy. The fibrous membranes with uniform fiber diameters and excellent disposability properties were formed. The ST/PVA ratio of fibers was optimized according to the disposability and tensile strength of the fibrous membranes. Disintegration of untreated and post‐treatment fibrous membrane with ST/PVA ratio of 3/1 was over 80% and 40%, respectively, and the tensile strength was improved over two times comparing with pure starch fibrous membrane.

Highly solvent-stable polyimide ultrafine fibrous membranes fabricated by a novel ultraviolet-assisted electrospinning technique via organo-soluble intrinsically negative photosensitive varnishes

Highly solvent-stable polyimide ultrafine fibrous membranes fabricated by a novel ultraviolet-assisted electrospinning technique via organo-soluble intrinsically negative photosensitive varnishes

Solvent‐resistant ultrafine nonwoven fibrous membranes by ultraviolet‐assisted electrospinning of organo‐soluble photosensitive polyimide resin

AbstractAn ultraviolet‐assisted electrospinning (UVAES) method was investigated to improve the solvent stability of soluble polyimide (PI) electrospun ultrafine fibrous membranes (UFMs) to assist in the development of fibrous polymeric materials with improved resistance to harsh environmental conditions and to expand the potential applications for such soft filaments. A preimidized soluble negative photosensitive polyimide (PSPI) was synthesized via an one‐step thermal polycondensation from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 1,1′‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3′‐trifluoromethylphenyl)methane (TFMDA). The PI resin was then fabricated into UFMs by both conventional electrospinning (ES) and UVAES with N,N‐dimethylacetamide (DMAc) as the solvent. During spinning, photo crosslinking reaction occurred, accompanied by simultaneous micro‐jets of PI‐UV ultrafine fibers in the UVAES procedure. This created fibers that were thermally stable at higher than 500°C, reflection over 77% of the 457‐nm‐ wavelength light, whiteness index (WI) higher than 83, and enhanced solvent resistance in DMAc. Generally speaking, compared with the PI UFMs fabricated by conventional ES procedure, the PI‐UV UFMs obtained by the newly‐developed UVAES procedure showed much superior solvent resistance, comparable thermal stability, slightly decreased optical reflectance and WI values, and reduced fiber diameters. These properties are of great value to future applications in microelectronics and wearable technology.

An ultraviolet-assisted electrospinning procedure of polyimide ultrafine fibrous membranes fabricated by ester-type negative photosensitive polyimide

An ultraviolet-assisted electrospinning (UVAES) procedure was performed using in situ photopolymerization during the electrospinning process to enhance the solvent resistance of polyimide (PI) ultrafine fibrous membranes (UFMs). The resultant PI UFMs were fabricated via solution electrospinning using photosensitive poly(amic acid ester) (PSPAE) modified with unsaturated double bond side chains as the main fiber-forming agent, diethylene glycol diacrylate as the crosslinker, and titanocene as the photoinitiator. The precursor PSPAE UFMs were prepared via both of normal electrospinning and UVAES procedures and then were converted to PI using thermal imidization at 350 °C in a nitrogen imidization. The physical and chemical properties of the obtained PI UFMs were subsequently studied. The fibers exposed to ultraviolet irradiation possessed a smooth surface morphology and maintained their fibrous structure after thermal imidization at elevated temperature as high as 350 °C in nitrogen, whereas the crosslink-free PSPAE fibers lost their fibrous structure after heating. Furthermore, as well as providing enhanced thermal decomposition stability, the introduction of a crosslinked structure via ultraviolet irradiation also protected the molecular chains from organic solvents, resulting in excellent solvent resistance of the PI UFMs.

Amphoteric Soy Protein-Rich Fibers for Rapid and Selective Adsorption and Desorption of Ionic Dyes.

Uniquely amphoteric soy protein (SP)-rich ultra-fine fibers (231 nm average diameter) have been facilely electrospun from aq. colloids and rendered water-insoluble by heating (150 °C, 12 h) to be highly stable over 14 d (pH 7) as well as under extremely acidic to basic (pH 0–10, 2 d) or at boil (2 h) conditions. The SP-rich fibrous membranes are easily tuned to be charged either negatively by deprotonation above or positively by protonation below the 4.5 PI of SPs. This pH-responsive amphoterism has been demonstrated for rapid adsorption of either cationic or anionic dyes, selective adsorption of either dye from their mixtures, and repetitive adsorption/desorption to recover and reuse both dyes and membranes. Chemisorption and heterogeneous adsorption of ionic dyes was confirmed by close fitting to the pseudo-second-order kinetic model (R2 = 0.9977–0.9999) and Freundlich adsorption isotherm (R2 = 0.9879). This is the first report of water-resilient and pH-robust ultrafine fibrous membranes fabricated from aqueous colloids of neat globular SPs, the major byproducts of under-utilized edible oil and biodiesel. The natural polyampholyte origin, amphoterism, and green processing make these fibrous materials unique and versatile for many potential applications involving both anionic and cationic species.

Polyphenylene Sulfide Ultrafine Fibrous Membrane Modified by Nanoscale ZIF-8 for Highly Effective Adsorption, Interception, and Recycling of Iodine Vapor.

In this study, two novel composite membranes containing nanoscale ZIF-8 and polyphenylene sulfide (PPS) nonwoven fabric were prepared via hydrothermal (PPS-ZIF-8) and biomimetic mineralization (PPS-ZIF-8-BSA; BSA, bovine serum albumin) approaches. The biomimetic mineralization approach in particular was extremely rapid and mild, and crystalline ZIF-8 was coated on the PPS substrate in only a few seconds at room temperature. The maximum iodine adsorption capacities of the PPS-ZIF-8 and PPS-ZIF-8-BSA membranes were 2.51 and 2.07 g/g, respectively. The composite fibrous membranes were able to capture trace iodine vapor under differential pressures ranging from 0 to 1000 Pa without almost any iodine vapor leakage. The composite membranes can be applied in harsh environments because of the excellent stability of ZIF-8 and the PPS high-performance fibers. This study provides a promising strategy to fabricate novel adsorption materials for the collection of radioactive iodine during nuclear waste disposal.

Target regulation of both VECs and VSMCs by dual-loading miRNA-126 and miRNA-145 in the bilayered electrospun membrane for small-diameter vascular regeneration.

Clinical utility of small-diameter vascular grafts is still challenging in blood vessel regeneration owing to thrombosis and intimal hyperplasia. To cope with the issues, modulation of gene expression via microRNAs (miRNAs) could be a feasible approach by rational regulating physiological activities of both vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). Our previous studies demonstrated that individually loaded miRNA-126 (miR-126) or miRNA-145 (miR-145) in the electrospun membranes showed the tendency to promote vascular regeneration. In this work, the bilayered electrospun graft in 1.5-mm diameter was developed by emulsion electrospinning to dual-load miR-126 and miR-145 for target regulation of both VECs and VSMCs, respectively. Accelerated release of miR-126 was achieved by introducing poly(ethylene glycol) in the inner electrospun poly(ethylene glycol)-b-poly(l-lactide-co-caprolactone) ultrafine fibrous membrane, reaching 61.3 ± 1.2% of the cumulative release in the initial 10 days, whereas the outer electrospun poly(l-lactide-co-glycolide) membrane composed of microfibers fulfilled prolonged release of miR-145 for about 56 days. In vivo tests suggested that dual-loading with miR-126 and miR-145 in the bilayered electrospun membranes could modulate both VECs and VSMCs for rapid endothelialization and hyperplasia inhibition as well. It is reasonably expected that dual target-delivery of miR-126 and miR-145 in the electrospun vascular grafts has effective potential for small-diameter vascular regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 371-382, 2019.

Novel Ultrafine Fibrous Poly(tetrafluoroethylene) Hollow Fiber Membrane Fabricated by Electrospinning.

Novel poly(tetrafluoroethylene) (PTFE) hollow fiber membranes were successfully fabricated by electrospinning, with ultrafine fibrous PTFE membranes as separation layers, while a porous glassfiber braided tube served as the supporting matrix. During this process, PTFE/poly(vinylalcohol) (PVA) ultrafine fibrous membranes were electrospun while covering the porous glassfiber braided tube; then, the nascent PTFE/PVA hollow fiber membrane was obtained. In the following sintering process, the spinning carrier PVA decomposed; meanwhile, the ultrafine fibrous PTFE membrane shrank inward so as to further integrate with the supporting matrix. Therefore, the ultrafine fibrous PTFE membranes had excellent interface bonding strength with the supporting matrix. Moreover, the obtained ultrafine fibrous PTFE hollow fiber membrane exhibited superior performances in terms of strong hydrophobicity (CA > 140°), high porosity (>70%), and sharp pore size distribution. The comprehensive properties indicated that the ultrafine fibrous PTFE hollow fiber membranes could have potentially useful applications in membrane contactors (MC), especially membrane distillation (MD) in harsh water environments.

Superhydrophobic Hexamethylene Diisocyanate Modified Hydrolyzed Polymers of Intrinsic Microporosity Electrospun Ultrafine Fibrous Membrane for the Adsorption of Organic Compounds and Oil/Water Separation

Polymers of intrinsic microporosity (PIMs) have gained significant research interest because of their successful applications in adsorption and separation. PIM-1 is the first and most studied member of this class because it shows specific interactions with some certain organic species. Chemical modification of PIM-1, which can be achieved by simply hydrolyzing the nitrile groups in the backbone, provides an advantage of tailoring its adsorption and separation performances. In this study, electrospinning of ultrafine fibers from hydrolyzed polymer of intrinsic microporosity (HPIM) and blends of hexamethylene diisocyanate (HMDI)/HPIM was achieved in several different ratios of HMDI/HPIM ranging from 1:9 to 1:1 (w/w). Bead-free and uniform fibers were obtained in the form of self-standing ultrafine fibrous membranes, which were then thermally treated at 150 °C to introduce chemical cross-linking between HMDI units and carbonyl groups of HPIM, resulting in HMDI-modified HPIM fibrous membranes (HMDI/HPIM-FMs)....

A Comparative Study of Poly(tetrafluoroethylene) Ultrafine Fibrous Porous Membranes Prepared by Electrospinning, Solution Blowing Spinning, and Electroblown Spinning

Poly(tetrafluoroethylene) (PTFE) fiber is a kind of high-performance fiber, which shows excellent performances and has been widely used in many fields. In this study, PTFE nanofiber membranes were prepared by electrospinning, solution blowing spinning (SBS), and electroblown spinning (EBS). Compared with other methods, the EBS method was more successful in producing excellent flexible, uniform, and continuous PTFE nanofiber membranes, with a mean diameter of approximately 414.54 nm, which was lower than the traditional electrospinning and SBS PTFE fiber diameters, 785.27 and 446.03 nm, respectively, and the diameter distribution of the EBS fiber was more uniform. The EBS PTFE fiber mat with a pore size of 0.74 µm was obtained, which was smaller than the traditional electrospinning (1.58 µm) and SBS (0.90 µm). The lower fiber diameter, smaller pore size, and better hydrophobicity made the EBS PTFE fiber mat more fit for thermal filtration and other applications compared with the electrospinning and SBS one.

Design and fabrication of imidazolium ion-immobilized electrospun polyurethane membranes with antibacterial activity

By covalently immobilizing imidazolium ion onto molecular chain, functional polyurethane (PU) is fabricated and thus an effective way is initiated to prepare electrospun membranes with antibacterial activity. In the experiment, PUs containing imidazolium ion side group (Bmim-PUs) are synthesized through a two-step polymerization process. It includes prepolymerization of isophorone diisocyanate (IPDI) with polyester glycol and chain extension polymerization using imidazolium-based ionic diol (Bmim-OH). Then, the obtained Bmim-PUs are electrospun into fibrous membranes with a diameter of ~640 nm. After a careful assessment, antibacterial activities of electrospun membranes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are clearly exhibited. The antibacterial efficiency of Bmim-PUs on both bacteria species improves by 60% in comparison with PU without imidazolium ion. This research suggests a simple but effective methodology to design and fabricate ultrafine fibrous membrane with significant antibacterial activity. Moreover, the obtained fibrous membranes have widely potential applications in protective textiles, filtration, and biomedical engineering.

Preparation and Mechanical Properties of Polystyrene Fibrous Membranes via Electrospinning

Polystyrene (PS) ultrafine fibrous membranes were prepared by electrospinning. The effects of PS molecular weightand auxiliary electrode on jet splitting behavior, fiber morphology and mechanical properties of the fiber nonwovens were investigated. The jet splitting behavior was examined by high-speed camera, the fiber morphology was observed with scanning electron microscopy, the mechanical properties of the membranes were measured with universal tensile machine. The results showed that, the stable jet length, the fiber diameters and the density of the mats are all increased in the presence of auxiliary electrode. The increase of polymer molecular weight postpones jet splitting, and enlarges fiber diameters and elevates the tensile strength of the membranes. Heat treatments of the membranes both at atmospheric pressure and high pressure significantly promote conglutination among filaments and heighten the tensile strength. The presence of solvent molecules in the fiber mats impairs mechanical properties to some extent when the two heat treatment modes are contrasted.

Electrospinning of ultrafine core/shell fibers for biomedical applications

Because of the inherent appearance similar to the natural extracellular matrix, ultrafine fibrous membranes prepared via electrospinning exhibit widespread applications, especially in the biomedical area. Extensional modifications of coaxial and emulsion electrospinning have drawn much attention in preparation of core/shell fibers for applications as tissue engineering scaffolds and controlled delivery systems for bioactive substances. Due to incorporation of multi-components in the electrospun core/shell fibers, the process of coaxial and emulsion electrospinning became more susceptible. The theories have not been fully understood. A series of investigations were carried out evaluating the systematic and processing parameters. This paper reviews advantages and potentials of electrospun core/shell fibers as well as factors influencing their formation on the basis of our research and new progress.

Preparation of high strength ultrafine polyvinyl chloride fibrous membrane and its adsorption of cationic dye

The polyvinyl chloride (PVC) ultrafine fibrous membranes were prepared by electrospinning. After solvent and thermal treatments, the membranes were used for the adsorption of cationic dye. The factors, the solvent ratio, the time of solvent treatment and the temperature of thermal treatment, were studied to enhance the mechanical properties of the membranes. The effects of the initial dye concentration and the solution temperature on the adsorption behaviors of the membranes were investigated. The results indicate that, long and uniform PVC ultrafine fibers were steadily electrospun at the PVC concentration of 10 w/v% in the mixture solvents of THF and DMF. The highest tensile strength of membranes reached 7.87 MPa, whereas the value of untreated counterpart was only 0.67 MPa. The equilibrium sorption capacity Qe increased with the increases of the initial dye concentration and solution temperature. The equilibrium adsorption of the membranes followed Freundlich isotherm and the adsorption kinetics observed Lagergren’s pseudo-second order equation.

Controlled release of siRNA nanoparticles loaded in a novel external stent prepared by emulsion electrospinning attenuates neointima hyperplasia in vein grafts

To evaluate a strategy of using TF siRNA loaded in a novel external stent prepared by hybrid ultrafine fibrous membrane consisting of PLGA/Chitosan nanoparticles as a therapy for vein graft disease. Hybrid ultrafine fibrous membranes consisting of PLGA/Chitosan nanoparticles were fabricated via a specially designed electrospinning setup. After soaking in chloroform to dissolve PLGA, the amount of chitosan in the hybrid membranes was determined. The water uptake of the hybrid ultrafine fibrous membranes was investigated by incubation in phosphate buffer solution. Right jugular vein-carotid artery interposition grafting models in Sprague-Dawley rats were randomly divided into five groups:Group A (external stent consisting of PLGA/CS-TFsiRNA nanoparticles), Group B (external stent consisting of PLGA/CS-Stealth(TM) RNAi negative control nanoparticles), Group C (external stent consisting of PLGA/CS blank nanoparticles), Group D (external stent consisting of PLGA), Group E (without perivenous external stent). BLOCK-iT(TM) Fluorescent Oligo was used to confirm its stability and successful transfer into the vein graft wall. The vein grafts were harvested at 1, 3, 7, 14, 28 d after operation, respectively. The TF protein expression of vein grafts was analyzed by Western blot and immunochemistry at 1, 3, 7 d after operation, respectively. The expression of proliferating cell nuclear antigen (PCNA) was identified by immunochemistry methods. The thickness of neointima at 28 d was calculated by computer imaging analysis system. The PLGA and CS amount in PLGA/Chitosan nanoparticles membranes could be well controlled by adjusting the flow rate for electrospinning of PLGA and chitosan nanoparticles, respectively. Because of the introduction of chitosan, which is a naturally hydrophilic polymer, the hybrid membranes exhibited good water absorption properties. BLOCK-iT(TM) Fluorescent Oligo could be detected in the graft wall even 12 days after operation. The expression of TF protein in Group A was significantly less than that in control groups at 3 d after operation (P < 0.05, 0.40 +/- 0.03 vs 0.75 +/- 0.01, 0.75 +/- 0.05, 0.77 +/- 0.07) and at 7 d after operation (P < 0.05, 0.30 +/- 0.03 vs 0.84 +/- 0.05, 0.86 +/- 0.06, 0.85 +/- 0.06). The expression of PCNA in Group A decreased significantly in comparison with control groups at 14 d after operation (P < 0.01, 13.0% +/- 2.6% vs 25.0% +/- 2.8%, 24.2% +/- 3.9%, 24.0% +/- 4.1%, 44.8% +/- 3.7%). The thickness of neointima at 28 d after grafting in Group A was significantly less than the untreated group (P < 0.01, 18.8 microm +/- 2.9 microm vs 38.7 microm +/- 5.0 microm, 37.3 microm +/- 3.6 microm, 37.2 microm +/- 2.6 microm, 67.5 microm +/- 4.8 microm). The novel external stent prepared by hybrid ultrafine fibrous membrane consisting of PLGA/Chitosan nanoparticles inhibits early neointima formation in rat vein grafts. This strategy may be a practicable and promising form of gene delivery against vein graft failure.